Tag Archives: urban freeways

Freeway Ramp Removal – the 134 at Colorado

Recently, we took a look at an opportunity to improve access to the LA River and create space for building a bunch of badly needed housing by eliminating some ramps on the 2 that were probably causing freeway congestion anyway.

There’s another set of ramps on the other side of Eagle Rock that could go, and while eliminating them wouldn’t do much for the freeway (which is rarely congested there anyway), it’s perhaps an even better development opportunity. If you know the area at all, you’ve already guessed that we’re talking about the long ramps from Colorado to the 134. As Walk Eagle Rock explained, these ramps are leftovers from an early interim terminus of the 134, when the state planned to run the freeway through Eagle Rock rather than the through the hills above it.


Like its companion on the 2, this interchange provides very limited function for traffic circulation. Traffic exiting the 134 westbound could exit at Figueroa, the same off-ramp with a terminus a little over a half mile away; traffic entering the 134 eastbound could simply continue on Colorado, turn left on Figueroa, and use the Figueroa on-ramp. According to our friends at Caltrans, the ramp volumes are pretty unimpressive. Assuming all the traffic from the Colorado ramps went to Figueroa instead, the combined ramps would certainly be the most heavily-travelled ramps between the 2 and the 210, but still well less-used than the 134 ramps in downtown Glendale.


This is a large area, so rather than detail a development concept, let’s just look at how much space we’d have to work with in general terms. The following table shows the freeway parcel areas (according to ZIMAS), and the number of housing units that could be developed on each at R3 (classic dingbat) and R4 (small podium) zoning density.


Of course, it’s probably not practical to develop the entire area as residential buildings; we are talking about 10 acres of land after all. Some roadways for circulation would be needed, and a little open space wouldn’t be bad despite the proximity of some other parks. Still, you could reserve 40% of the space for other uses and produce about 650 units of housing at R4 density, all without demolishing any existing buildings. R4 is probably not an unfair assumption, as some nearby commercial zones are C4, which allows R4 uses.

In addition to bureaucratic challenges, you’d have to get rid of the existing pavement and utilities, which shouldn’t be a huge deal. The ramps are elevated, which means you’d probably have a large amount of earth to move, but there’s an old saying in civil engineering that earthworks are cheap, and there’s always someone looking for good fill. While it wouldn’t help freeway operations, this project would take six bridges off of the Caltrans roster, and they can’t be the newest bridges around, so maybe there’s some long-term maintenance savings there.

All in all, it seems like a possibility at least worth exploring in more detail.

Freeway Ramps and Crosswalks

We haven’t had a freeway post in a long time, but a while back we talked about short-term improvements that can improve the interface between freeways and city streets for pedestrians and bicyclists. The principle goal is to reset drivers’ minds for the urban environment by forcing them to slow down or stop when exiting the freeway, so that they don’t hit city streets at freeway speeds. The best designs for this are the tight diamond and the tight four-ramp partial cloverleaf.

Ideally, we’d like to also strengthen pedestrian connections by providing crosswalks on the city street that would run concurrent with the freeway off-ramp. The city street is often a major arterial road where the crosswalk spacing is too large, and a crosswalk at the ramp would help alleviate that problem.


Here are two locations where such crosswalks were actually installed.

First, the 134 and Glendale Ave:

Second, the 134 and Pacific St:

Nice work, Glendale, on getting those tight diamonds, tight four-ramp partial cloverleaves, and extra crosswalks!

However, freeway ramps are not great locations for crosswalks. At most intersections, the majority of traffic goes straight, with smaller turning volumes, making it feasible to have concurrent pedestrian movements without much danger to pedestrians or impact to traffic capacity. At freeway ramps, though, the situation is reversed. Almost all traffic is turning, so concurrent pedestrian movements create danger to pedestrians and significantly reduce traffic capacity. While pedestrian safety can be improved at such intersections with a leading pedestrian interval, the other problems remain.

Fortunately, there’s a way around this issue that improves pedestrian connections, has a low impact on traffic capacity, and serves the goal of forcing drivers to adjust to city driving conditions. We can simply move the ramp crosswalks away from the freeway, and synchronize the traffic lights so that the crosswalk movement is concurrent with the ramps.


This creates space for the traffic exiting the freeway to queue up. Since drivers exiting the freeway will always encounter a red light at the crosswalk, they will be forced to stop and reset their minds. Pedestrians do not have to contend with conflicting traffic, and the location of the crosswalk might better serve them. A crosswalk adjacent to a freeway will be located such that the freeway is occupying much of the nearby street frontage, whereas a crosswalk further away will serve more development.

If there’s an unsignalled minor street nearby, that’s a natural location for a new traffic signal and the crosswalk. Let’s look at a few examples around the county.

The 134 & Pacific in Glendale:


The 10 & Normandie in LA:


The 405 & Artesia in Torrance:


The 405 & Western in Torrance/LA:


These improvements obviously require new traffic signals, which is a considerable expense. Therefore, they should be rolled into either freeway improvement projects or arterial corridor improvements. The pedestrian signal is only a simple two-phase signal, and doesn’t need much intelligence since it will be synchronized with the ramp, which will help some with costs, especially if part of a larger job.

Eliminating Loop Ramps: The 10 at La Cienega and La Brea

In this introductory post on urban freeway improvements, the elimination of loop ramps and slip ramps was identified as some of the lowest-hanging fruit. It’s relatively cheap to do, and it makes things much better for bikes and pedestrians by getting rid of long, skewed crosswalks and road geometry that encourages drivers to speed. Since loops take up a lot of real estate, it also frees up a decent amount of land for development. Inspired by a recent comment, here’s a look at two interchanges on the 10: La Cienega and La Brea.

La Cienega

The westbound ramps at La Cienega are already in a tight diamond configuration, so there’s nothing to change there. The eastbound ramps are in a cloverleaf configuration, albeit a modified one, since Venice cuts through the vicinity. Thus, the northbound La Cienega on ramp to the 10 eastbound is a right on Venice, then a right on the ramp. The loops are very tight, with curve radii down in the neighborhood of 80’.

The basic idea here would be to remake the eastbound ramps in the image of the westbound ones. The interchange would become a modified tight diamond, with a new road connecting the two ramps between La Cienega and Venice. This would reconfigure the free movements to and from the ramps into normal city intersections, making them less hazardous for pedestrians and bikes. It would also yield new signalized pedestrian crossings of La Cienega and Venice, making things a little more walkable.


click to embiggen

This concept uses 10’ lanes and 6’ curbside bike lanes on La Cienega. Now, I know what you’re thinking – why is there no crosswalk on the north side of the intersection of the new ramps and La Cienega? Three-legged pedestrian crossings are horrible! The reasoning is that adding a crosswalk there makes things considerably harder for the traffic engineering, and this location is a rare exception to the rule that you should never omit a crosswalk. Because there’s nothing on either side of La Cienega on that side of the ramps, there’s no chance a pedestrian would have to use all three crosswalks in lieu of the missing crosswalk. Anybody walking here is going to either a destination north of the 10, in which case they can cross at David Ave and the onramp to the 10 westbound, or a destination south of the new ramps, in which case they can cross on the south side of the intersection.

This concept adds two lanes under the freeway bridge. It looks like this might just fit under the existing bridge, because the east side has a row of parking between the existing edge of pavement and the columns.

On the traffic side, the loop ramps are both serving over 10,000 vehicles per day. Those turning movements, which are currently free (unsignalized) right turns, will be replaced with left turn phases at the new traffic signal. Excluding the crosswalk on the north side of the intersection makes that left turn easier, reducing the green time needed for the eastbound movement. Again, this is only acceptable because it’s a special situation. Here are the traffic volumes at the new intersection.

LaCienega-table1 LaCienega-table2 LaCienega-sketch

Traffic volumes are from Caltrans and LADOT. This is a really rough estimate. The approach was to guess at the worst conflict group (combination of movements that can’t proceed at the same time) for each intersection, and figure out the sum of capacities needed for each movement in the group. That’s the “g/C” column (green time divided by cycle time), representing the percentage of the total intersection capacity needed for that movement. For example, the left turn from the 10 eastbound to La Cienega northbound needs 23% of the capacity at the intersection. If the total of that column is greater than 100%, or even relatively close, the intersection is close to failing.

La Brea

The existing interchange at La Brea is a full cloverleaf, with loops almost as tight as 100’ radius. However, the interchange doesn’t function like a true cloverleaf, because the outer ramps have very sharp cure radii to and from La Brea, and the offramps using the outer ramps have traffic lights instead of free-flowing turns.

The plan at La Brea would be to reconfigure the interchange as a tight diamond, using the same parameters – 10’ lanes, 6’ bike lanes. There are two options, one with the ramps tight up against the freeway, and one with the ramps intersecting La Brea near where the outer ramps do today.


click to embiggen


it’s a perfectly cromulent word

The advantage of the first option is that it lets you do the same crosswalk trick as at La Brea. However, unlike at La Cienega, there’s no extra room under the freeway at La Brea. We can steal the weaving lane to get four lanes under the bridge, but that leaves only a single lane for the left turns onto the 10. Unfortunately, that probably won’t work on the traffic side.

By pushing the ramps further away from the bridge, the second option lets you fit in a second left turn lane, though due to the lane’s short length, it might be a little optimistic to assume it could be used to its full capacity. Also, because the second option puts the new development between the ramp intersections, it’s no longer acceptable to omit a crosswalk. That makes the traffic design more challenging.

Traffic volumes on La Brea are daunting – the road serves nearly 70,000 vehicles per day here, more than many freeways that are two lanes per direction. The heaviest ramp volumes are to and from the east, all approaching 10,000 vehicles per day.

LaBrea-table1 LaBrea-table2 LaBrea-sketch

This design would require the crosswalks closest to the freeway to be concurrent with the left turns from the freeway offramps, which might be difficult given the traffic volumes.

Palmer Paradise

Now normally this is the part of the post where I’d suggest auctioning off the real estate to the highest bidder, as long as they agree to do something with it other than surface parking. That way you don’t end up with prime real estate owned by the government sitting vacant for years because it was impossible to come to a consensus on what to do with the land.

But you know what? F!@# it. These freeway-adjacent sites are right in GH Palmer’s wheelhouse. Just dial him up and let’s get us a few hundred Italianate apartments built. We can call them The Palude and The Catrame (the Italian equivalent of La Cienega and La Brea).

Traffic Troubles

While the idea of improving these interchanges for pedestrians and bikes, and freeing up space for urban development, is appealing, the worst g/C ratios approach 1 at both interchanges. More traffic study would certainly be required to see if these plans are viable.

Politically, any plan to eliminate loop ramps is going to have to win the support, or at least the grudging tolerance, of drivers. Unfortunately, these interchanges are not the best candidates for the first project, because if the first project doesn’t go well, there won’t be any more. Back to the lab again. . .

 The sausage-making behind this rough traffic analysis: I assumed the ramp volumes have the same peaking as the through movements on the 10, and 1,700 veh/hr capacity for each lane at the intersections. The critical conflict group at La Cienega was assumed to be Offramp EB – La Cienega NB – La Cienega SB left turn. At Venice, Onramp EB (from the La Cienega SB left turn) – Venice EB – Venice WB left turn. No volume was available for the last movement so it was a wild guess. The critical conflict groups at La Brea were assumed to be Offramp EB – La Brea NB – La Brea SB left turn, and Offramp WB – La Brea SB – La Brea NB left turn.

Congestion Pricing Questions

Congestion pricing for freeway capacity is a hot topic. The basic implementation of price-managed lanes known as high-occupancy toll (HOT) lanes has been rolled out in many cities, including the new lanes on the Capitol Beltway in Virginia and the retrofit of existing HOV lanes on the 110 and the 10. These lanes operate on a simple principle: when traffic increases in the lane, prices (tolls) are increased to decrease the number of people using the lane and prevent congestion.

Beyond that, though, a wide range of people have called for congestion pricing on all lanes of freeways. This ranges from libertarians who favor user fees, like Randal O’Toole, to urbanists that want to decrease the amount of driving by increasing costs, to cities and states that see potential revenues.

Theoretically, it is easy to extend the concept of HOT lanes to the entire freeway. However, it seems to me that to do so, you have to make a major simplifying assumption about your freeway network – that there are no capacity mismatches. What does that mean? It’s probably easiest to show by way of a few examples. Note that traffic jams on freeways do not necessarily indicate there’s a problem on the road at that location; rather, they are often acting as a queue of cars, pointing towards a downstream bottleneck. There are also questions for long distance trips.

The Off-Ramp Strangler: The 10 at Cloverfield

On weekday mornings, the 10 westbound into Santa Monica backs up starting at the Cloverfield/26th off-ramp. There’s a lot of employment in the area around the future Olympic/26th Expo Line station, and the local streets can’t handle the traffic volumes at peak times. The off-ramp acts as storage for cars waiting to distribute themselves on the local street network, and when the off-ramp gets full, cars start queuing up on the mainline of the freeway.



If you’re managing an HOT lane, it’s pretty easy to keep that lane flowing at a reasonable speed. You’d just charge a higher toll for the lane up to Cloverfield, and then a lower toll beyond that. The general purpose lanes act as a spillway, soaking up whatever traffic comes out of the HOT lane.

What would happen in practice if the whole freeway was tolled? Some people will try to change their travel patterns by leaving earlier or later, which is the real intent of congestion pricing. However, some people will just hop out onto the free local street network. If you charge an arm and a leg to get from Bundy to Cloverfield, maybe I decide to get off at National, Overland, or Bundy. That moves the queue of cars trying to get to office parks in Santa Monica off of the freeway and onto the arterial grid.

Disastrous Lane Drop: The 5 at Norwalk Narrows

Everyone in LA has probably experienced this at some point: you’re cruising north on the 5 in Orange County, enjoying some of the world’s finest freeway engineering, and then boom! You pass the 91 and you slam (figuratively, we hope) into gridlock on the three-lane section of the 5 through Santa Fe Springs and Norwalk. This is one of the last unreconstructed 1950s-era freeways in LA. It’s being widened as we speak, but it’s a great example of a capacity mismatch between adjacent sections of a freeway mainline.



If you’ve got a managed HOT lane here (and the Orange County section is clearly designed for that possibility), you can keep it flowing by charging a punitive toll through the Norwalk Narrows. If the entire freeway is tolled, you’d have to charge very high tolls to keep things moving on the three-lane section – so high, that you might not be able to charge anything on the five-lane section to the south. That results in a very cheap section leading into a very expensive section.

Again, the incentive is going to be for people to use the cheap section of the freeway, and then bail out onto the free local arterial grid.

Alternatives with Issues: The 405 vs North-South Arterials

This one isn’t quite so much about a freeway capacity mismatch as it is about the amount of existing congestion on local arterials.

Northbound congestion on the 405 has several causes. For one, the prolonged steep grade approaching Sepulveda Pass degrades vehicle performance, resulting in some vehicles slowing down. At the top of the pass, you have an intense weaving section leading up to the busiest interchange in the country, the 405 and the 101. Further upstream, you simply have a lot of traffic from Westside employment centers entering the freeway between the 10 and Wilshire to head home to the Valley.


Contrary to popular conceptions of LA, the north-south arterials on the Westside are significantly underpowered. Sepulveda is the only true through arterial between Lincoln and Robertson; the rest – Bundy-Centinella, Sawtelle, Barrington-McLaughlin, Westwood-Overland, Beverly-Beverwil-Castle Heights – are Frankenroads, incomplete, cobbled together from various parts, and not even two lanes in each direction. This contributes to a major lack of north-south mobility on the Westside.

If the 405 were tolled to maintain higher speeds, some traffic would shift to this free ragtag network of north-south arterials. Again, this might be an undesired side effect of tolling all freeway capacity.

Long-Distance Trips

Existing HOT lanes, like the express lanes on the 110 and the 10, are managed dynamically: prices are adjusted to respond to real-time traffic conditions. If the lane starts to get congested, prices are increased to reduce the number of drivers that decide to enter. Pricing information is conveyed to drivers using variable message signs. If you’re already in the lane, the price you saw when you entered is honored for your destination.

This works well for a managed HOT lane in isolation; no one knows what the toll will be when they enter the freeway, so the general purpose lanes just soak up whatever traffic doesn’t want to use the HOT lane. With a network of HOT lanes, this will still work pretty well. The number of destinations you can reasonably indicate on a VMS sign is limited, but you’d always have the option to leave when you reach the next tolling section. Let’s say you’re in the HOT lane on the 10 east and you hop on the 5 south to go visit the mouse, and you don’t like the prices. No problem, you just take the free lanes.

If the entire freeway is dynamically tolled, this starts to fall apart. What do I do if I get on a freeway and I’m not willing to pay the going price? For short trips, you could check before you leave, but for long trips, it would be an issue. If you get on the 101 in Woodland Hills and you’re going to Anaheim, what happens if you get on the 5 and the toll is more than you’re willing to pay? Do you take arterials? Do you just get off and park somewhere, waiting for prices to go down?

Private Parts

Now, you may have been chomping at the bit as you read this post, thinking that there are technological solutions to these problems: use congestion pricing on the arterials as well as the freeways, and quote people a price for their entire trip before they start it.

Those ideas are certainly theoretically possible. However, they may prove politically impossible, for some very good reasons.

Tolling arterial capacity, using existing electronic tolling methods, would prove unreasonably costly. It would more or less require turning every traffic light into a tolling location. It would require trying to communicate toll rates on a block by block basis. Both of these would be impractical. You could do it without any roadside equipment by requiring every vehicle to be equipped with GPS, and having the vehicle’s on-board equipment report the GPS data to a central facility for calculation of tolls.

Getting a price quote for a trip before you take it is something we’re all familiar with for things like flying, ferries, tours, and so on. In the case of flying, the details of your travel are reported to the government in advance. However, flying is something most people do rarely. Requiring advance requests for auto travel fees would bring that level of oversight into people’s everyday lives.

To be blunt, I don’t think many people would be comfortable with having to tell the government where they’re going before they leave, and I don’t think many people want their movements being tracked by GPS. If you don’t like the NSA recording your phone calls and reading your emails, you should be worried about the prospect of having the government follow your whereabouts. While this would obviously still leave walking, biking, and transit as options for anonymous travel, it would be an imposition on people’s right to freedom of movement.


This isn’t to say we should give up on the idea of tolling highway capacity. I would be curious to see research on detailed modeling of a real road network (freeways and arterials) under these scenarios. For example, what would happen on the Westside if the 405 and the 10 were dynamically tolled but the arterials were still free? Regarding privacy, would people be more comfortable if the advance price was obtained through a third-party intermediary (such a car-sharing service) that could make the reservation with the system in the corporation’s name?

In the meantime, a more realistic option than real-time dynamic pricing might be managing freeway capacity the way that street parking is managed in downtown LA. In that model, utilization of street parking is monitored, and then prices at different times of day are adjusted up or down to try to optimize utilization. For freeways, a schedule of prices could be published and updated every month, so that users would be able to determine prices before they leave.  For example, say that in August 2014 it costs $0.25 to go from La Cienega to Robertson on the 10 on weekdays at 12:30pm, and the level of congestion is still too high. The rate for September would be increased to $0.30 or $0.35.

In the case of capacity mismatches, it might be desirable to deliberately underprice freeway capacity so that the amount of traffic diverted to arterials isn’t too large. Many people would rather have a queue of cars on the freeway, leaving arterials a little less congested and available for things like local trips and emergency vehicles.

Congestion pricing has great potential to improve mobility in urban regions. But the devil’s in the details, and we don’t have them worked out just yet.

Brighten Up the Bottomside of the 10

Wut, another freeway post?

We’ve talked before about the need to think about short-term improvements to freeways that strengthen the city fabric and make streets safer and more comfortable for bikes and pedestrians. That post was really geared towards everything on the surface of freeways and interchanges, but what about the area underneath freeway viaducts? There are things that could be done in the short term to improve these environments too.

Keep Houston Houston already did the legwork on this one; here’s the quick takeaway on how the undersides of viaducts and bridges should be designed:

  • Face with a solid surface. Beams and trusses create cavities that get filled with trash, guano deposits, and in some cases, affordable housing. California has an advantage here because most of our freeway bridges are continuous reinforced slabs or box girders, which already have a smooth, solid, continuous underside.
  • Paint a bright color, for obvious reasons.
  • Illuminate with bright lighting, also for obvious reasons. The lights used should be cool white LEDs, which produce a more appealing light spectrum. Traditionally, this type of outdoor lighting has been done with sodium vapor lamps, which are cheap and bright, but produce that characteristic industrial yellow glow. However, LED capital and operating costs have fallen to the point where they’re practical.
  • Bump up the level of density and activity abutting the freeway. If you want it in Jacobsian terms, a freeway viaduct is a long, skinny border vacuum. Making each side more active helps bridge the gap.

Quick Fix Bridges

For a simple case, here’s how things look today in Palms, on National underneath the 10:

What does this need? New lighting fixtures, a coat of white paint on top, and maybe some murals from local artists on the walls. This can be done quickly and for low cost. Here, enjoy an awesome MS Paint rendering of the same:


In some places, there’s already been some progress. For example, in Santa Monica, Pico was spruced up where it goes under the 10. It’s not all the way there, but it’s a start:

A Little More Work for Viaducts

I think the most interesting candidate for improvement right now is the 10 between the 110 and Olive Street. This area has already seen significant infrastructure investment in the Expo Line, and more is hopefully on the way with My Figueroa. On the north, the area bounded by the 10, the 110, 7th, and Hill is one of the hottest development markets around. To the south, USC has plans to develop new buildings, in addition to the massive Lorenzo project.

This makes the 10 viaduct a good candidate for enhancement, since it would contribute to growth in the area by making the street fabric more inviting for walking and biking. The 10 viaduct continues all the way to the river, of course, but east of Hill things are more industrial, so focusing on the stretch from the 110 to Olive will give the most bang for the buck.


Viaducts are a little harder to deal with than simple underpasses, because they create a long continuous break in the city. Often, the space underneath is used for low end uses like car or bus parking, partly because it’s not exactly a pleasant area and partly because those uses can easily be moved if you need to do maintenance.

However, it’s possible to locate more active land uses under freeway viaducts. It’s probably not a good location for apartments, but commercial, retail, and light industrial uses can work. For example, here’s some simple commercial/retail uses under the 10 between Olive and Hill:

And here’s a building (with unfortunately solid walls) under the 10 at National and Robertson:

If we look beyond LA, here’s a supermarket under the rusting hulk of the West Side Highway in Manhattan. It was always pretty busy whenever I visited:

Or try on this example near Smith-9th in Brooklyn, with a 4-track railroad viaduct going over buildings.

The key is having enough of an active city around the viaduct that it can support those retail or restaurant uses. As the corridor between LA Live and USC continues to grow, that’ll happen. I’m sure some enterprising businessperson can figure out how to turn the challenges into opportunities. For example, I’m told that exposed concrete columns are more authentic than drywall, and can be an attractive design feature in a building. Another opportunity would be to use the transverse gaps in the viaduct, say near Flower and Figueroa, to create interesting architectural features that would channel sunlight to the insides of the buildings underneath.

Maintenance Matters

Like anything, a big question is how much this will cost and who will pay for it. Caltrans probably isn’t interested in doing anything other than meeting their core mission of keeping these things in a state of good repair. The city probably isn’t interested in picking up the tab for upkeep like painting and washing either. With all the development in the area, maybe there’s an opportunity for a business improvement district to be organized to be in charge of such a project, which would increase property values in the area.

Again, it’s important to look for easy opportunities like this to make short-term improvements to the city. There’s probably more disagreement about the long-term disposition of urban freeways, but that shouldn’t stop us from doing what we can quickly to make the city a better place.

The 101 – Four-Level to Hollywood Split

‘Bout time for a freeway post, no? Prerequisite: principles for urban freeway improvements.

When it opened in 1954, the 101 was a revolution in freeway engineering, incorporating many lessons engineers had learned on earlier efforts. Gone were the tight corners of the 110, and interchanges now had acceleration/deceleration lanes. Breakdown lanes also appeared.

However, the 101 also features the typical shortcoming of 50s-era freeways: interchanges are spaced too close together. Maybe engineers expected lower speeds or smaller volumes, or maybe they just didn’t understand the impact of weaving. Either way, with distant rumblings about the need to widen the 101 – an expensive and disruptive endeavor for sure – it’s time to offer an alternative that helps improves traffic and coincidentally improves the city too. (Or, look at the other way around if you want.)

One good aspect of 1950s freeway engineering is that it usually didn’t blow enormous holes in the street grid to shave a few seconds off motorist delay at offramps and onramps. Instead, ramps are cleverly feathered into the street grid. Consider a typical interchange on the 101 (left) compared to the 105 (right).


So the biggest thing to fix on the 101 is interchange spacing. As a general rule, urban freeway interchanges should be spaced like rapid transit stops: about every mile. Ramps spaced less than a mile apart are counterproductive unless you go to the expense of braiding them, which costs a lot of money and disrupts the city – the opposite of what we want to do here. Don’t take my word for it, ask the folks who wrote the book on freeways. A quick look at the 101 shows that they apparently stuffed in as many ramps as they possibly could, regardless of whether the local street warranted it.


First step, figure out the interchanges. We’ll revisit the design of each in more detail later. Courtesy of our friends at Caltrans, here are ramp volumes for the 101. I used all 2006 data, because this was the most complete set. Numbers marked with a star are 2007 data. The changes since 2006-2007 have been trivial, and reflect a time of very high unemployment anyway. I’ve arranged the data so that complimentary moves are next to each other (e.g. northbound off and southbound on).


Shooting for an interchange every mile, and trying to can the low volume ramps first, here’s my rough layout. Mileposts start from the freeway center of the universe in East LA.

  • Four-Level Interchange (MP 3.1)
  • Alvarado (MP 4.4)
  • Silver Lake (MP 5.3, NB off & SB on only)
  • Vermont (MP 5.9)
  • Santa Monica/Western (MP 7.3)
  • Hollywood (MP 8.0)
  • Franklin/Vine (MP 8.6, NB on & SF off only)
  • Cahuenga (MP 9.0, SB off & SB on only)
  • Highland (MP 9.5)
  • Barham/Universal Studios (MP 11.1)
  • Campo de Cahuenga (MP 12.1)
  • Hollywood Split (MP 13.0)

Ten miles, eleven interchanges.

Note: in all the graphics, green is freeway replaced with undeveloped land. Orange represents land to be developed with new buildings.

Four-Level Interchange

I’m still leaving this one alone for a future post. For now, let’s say that obviously, we’re going to have an interchange with the 110.

Alvarado St

The ramps to/from Echo Park Av (northbound) and Union Av (southbound) are too close to both the 110 ramps and the Alvarado ramps, and they dump freeway traffic onto local streets. The NB off/SB on pair has higher volume than Alvarado, but that may be due to people using those ramps to avoid traffic on the 101 as soon (or for as long) as possible. No one using those ramps would have to go more than 0.7 miles out of their way to get to Alvarado.

Therefore, the Echo Park and Union ramps should be eliminated. The street grid would be reconnected and some property would be redeveloped. No changes are needed at Alvarado, which is a tight diamond.


Silver Lake Blvd

The ramps to/from Rampart Blvd and Benton Way are too close to both the Alvarado ramps and the Silver Lake ramps, and they too dump freeway traffic onto local streets. Closing these low volume ramps would be only a minor inconvenience to those drivers, who would have to travel a maximum of 0.6 miles to get to Alvarado. These ramps should be eliminated.

Meanwhile, the Silver Lake ramps are heavily directionally biased – that is, volumes to and from the south are much higher than volumes to and from the north. (See the ramp volume table; NB off/SB on are much larger than SB off/NB on.) The SB off and NB on ramps are also very close to the Vermont ramps, making for a punishing weave section on the 101. While it’s usually bad practice to not offer all ramp movements at every interchange, in this case an exception is warranted. The SB off and NB on ramps at Silver Lake should be eliminated. No one would have to drive more than about a mile out of their way due to this change.

Again, this would allow the street grid to be reconnected and some property to be redeveloped. No changes are needed at Silver Lake, which is a tight diamond.


Vermont Av

Vermont has by far the highest volume NB off/SB on ramp pair, and the SB off/NB on ramp pair volume is large as well. This interchange is definitely staying.

That creates an interesting question regarding the ramps at Melrose and Normandie. The SB off/NB on ramp pair volume isn’t that bad, but the NB off/SB on pair is high – in fact, the second highest such pair in the corridor. Eliminating those ramps is a tall order, but if they’re not eliminated, they probably need to be braided – the opposite of what we’re trying to accomplish here.

As luck would have it, an accident of history created an opportunity to solve this problem. The median of the 101 is very wide, up to 160’, between Virgil and Melrose. Students of LA freeway history will recall that this is because it was planned to be the location of a freeway interchange between the 101 and the 2, which was to be extended from Echo Park west to Beverly Hills and Santa Monica.

That freeway is never getting built, and the wide median is currently occupied by a self-storage facility. Time to put it to better use.

Between Virgil and Vermont, the southbound side of the 101 would be shifted north. There’s already an empty bay in the middle of the Vermont Av bridge that was reserved for the 2 freeway, so there’s no need to do any work on it. From Vermont to Melrose, both sides of the 101 would be shifted towards the middle, eliminating the wide median. New frontage roads would be constructed from Vermont to Melrose, accommodating the traffic currently using the NB off/SB on pair at Melrose/Normandie.

Finally, the Vermont ramps would be reconfigured to square up the intersections, eliminate traffic lights, and free up land for development. In particular, note the relocation of the SB onramp to line up with Rosewood Av and the new frontage road. This allows Oakwood St to be reconnected and for new development on the north side of Oakwood to screen the freeway.


Santa Monica Blvd/Western Av and Hollywood Blvd

Things are a little bit simpler at Santa Monica, Western, and Hollywood. There’s no need to modify those interchanges. The partial interchange at Sunset/Wilton has high volumes for the NB off/SB on pair, but it’s just too close to the Santa Monica/Western ramps. I’d expect most of that traffic to shift to the Hollywood interchange, which currently has smaller volumes. The SB offramp to Sunset isn’t a huge issue because it’s braided, but its volume is pretty low. That ramp and the SB onramp from Hollywood would be modified into a frontage road and onramp, reconnecting a north-south street in the adjoining neighborhood.


The changes on the southbound side aren’t that big, but eliminating the loop on the NB offramp frees up a lot of land for development and is a huge improvement to the pedestrian environment at Sunset and Wilton.

Franklin/Vine and Cahuenga

The ramps to/from Gower St and Argyle Av are all low volume ramps. They can be eliminated without much issue. The SB offramps to Cahuenga and Franklin/Vine are both high volume ramps, as is the NB onramp from Franklin/Argyle, so they remain. The SB onramp from Cahuenga should remain just because there needs to be a SB onramp somewhere in the area. The NB offramp to Cahuenga should be eliminated, since it is a low volume ramp and creates a murderous weave with the high volume NB onramp from Franklin/Argyle.

Another option would be to replace the braided SB ramps, on from Cahuenga and off to Franklin/Vine, with a frontage road and SB onramp. This would eliminate a couple bridges over city streets, and free up land on the north side of Franklin for development.



The SB off/NB on ramp pair at Highland is the highest volume ramp pair on the whole corridor, and it’s in a very logical and undisruptive location. That pair is definitely staying. The NB offramp to Highland needs to stay, just to have a ramp in the area, since the Gower and Cahuenga offramps would be eliminated. It’s closer than ideal to the Franklin/Argyle onramp, but so it goes.

The SB onramp from Highland should remain but be closed except when events are ending at the Hollywood Bowl. It’s much too close to the Cahuenga offramp for everyday operations, but it makes sense to keep it for Hollywood Bowl events so that the large bursts of traffic from those events don’t have to go through city streets to get to the freeway.


The NB off/SB on pair at Barham has fairly high volumes. The NB on ramp at Cahuenga near Pilgrimage Bridge also has high volumes and should remain. The NB offramp to Universal Studios is lower volume, but can remain because it’s not taking up useful real estate or causing any major weave problems. The NB onramp at Universal Studios should also remain.

For reasons unknown to me, the original NB off/SB on pair at Barham was abandoned long ago – all the way back in 1957, according to California Highways. If it can be reactivated, the original NB offramp would increase weaving distance between the Cahuenga onramp and the Barham offramp. However, that might encourage drivers entering northbound at Highland to try to cut across to Barham, which is a major weave and therefore undesirable. Instead, perhaps the Cahuenga onramp to northbound could be relocated south to increase the weaving distance between it and Barham.

Campo de Cahuenga

The Lankershim NB off/SB on ramp pair has larger volumes than Campo de Cahuenga, but it’s too close to the Barham ramps. In addition, eliminating the ramps at Lankershim would improve the pedestrian environment. Pedestrian volumes should be lower on Campo de Cahuenga because there’s nothing there. A SB offramp should be constructed at Campo de Cahuenga, and all movements provided for the NB ramps. The Campo de Cahuenga interchange would replace both the Lankershim interchange and the Vineland interchange, which is too close to the Hollywood Split.


This frees up land for redevelopment on Vineland where the SB loop ramps would be eliminated.


Hollywood Split

The Hollywood Split, with its missing ramps and left-hand exits and entrances, is a project unto itself. I’m going to leave it alone for the time being.

Implementation Timeline

Some of these improvements require building new ramps, which would require more traffic studies and engineering design than easier locations where ramps would just be eliminated. There’s no reason to hold up the easy projects to wait for the more complicated ones to be ready for construction; the easy ones could be completed in less than a year. A few improvements could be accomplished in the midterm, e.g. closing braided ramps with bridges that would need to be demolished. I’d break things down as follows.

Short-term improvements (<1 year):

  • Close Echo Park Av & Union Av ramps
  • Close Rampard Blvd & Benton Way ramps
  • Close Silver Lake Blvd SB off/NB on ramp pair
  • Close Normandie Av/Melrose Blvd SB off/NB on ramp pair
  • Close Sunset Blvd/Wilton Pl NB off/SB on ramp pair
  • Close Gower St/Argyle Av NB off/SB on ramp pair
  • Close Cahuenga Blvd NB offramp
  • Close Highland Av SB onramp
  • Close Vineland Av NB offramp

Mid-term improvements (1-3 years):

  • Close and demolish Sunset Blvd SB offramp
  • Close and demolish Gower St SB offramp

Long-term improvements (3+ years):

  • Close Normandie Av/Melrose Blvd NB off/SB on ramp pair, realign the 101 mainline lanes, and build frontage roads between Vermont Av & Melrose Blvd
  • Close and demolish Franklin Av/Vine St SB offramp, construct SB frontage road between Cahuenga Blvd & Franklin Av/Vine St, and reconstruct Cahuenga Blvd SB onramp
  • Complete tight diamond interchange at Campo de Cahuenga, close Vineland  St SB off/SB on ramps, close Lankershim Blvd ramps

Staging the implementation allows low-cost improvements to be constructed first. In fact, almost no upfront expenditure would be necessary for the short-term improvements if the land was sold for development, since the developers would assume the cost of removing the existing ramps. This would create some immediate benefits while long-term improvements were studied in more detail.


I know a lot of people really, really don’t like urban freeways. But just saying “tear them down” is a throwaway response that ignores the related issues like land use controls and the role of transportation in cities and economies. It also misses out on opportunities to improve the city that can be made quickly and low cost. The 101, as LA’s first real freeway, is a great place to start, and a successful project here could lead to more short-term improvements across the city.

How Many Parks Does a Civic Center Need?

In previous posts, I laid out some reasons for focusing some attention on the area between 2nd St and Union Station, and presented an option for improving the 101 in a way that would help restore the urban fabric between downtown and Chinatown. I was originally going to do two more posts, one on land use and one on parks, but they’re so connected that it makes sense to address them at the same time.

Concerning land use, by far the biggest problem in this area is the monolithic area of government buildings, and the accompanying parking uses. In the image below, based on the city’s excellent ZIMAS service, land zoned for public facilities (PF, i.e. government buildings, freeways, schools, fire stations, and so on) is colored blue-green. Other uses per the generalized zoning legend.

2nd-Union Zoning

The heavy concentration of a particular type of employment, while it creates agglomeration effects, results in inefficient use of infrastructure and land. Infrastructure use is heavy during peak travel periods, and businesses are crowded during  workweek lunch times, but the area is practically a ghost town at other times – try hanging out on Temple on a Saturday night, for example. In fact, the blue-green area pretty much corresponds to the district in question.

This is an important thing to keep in mind when it comes to the parks in this area, because the biggest determinant of a park’s success or failure is everything around it. The parks are shown in dark green in the ZIMAS image above.

Grand Park

As one can see, Grand Park is entirely surrounded by government buildings. Some hope that it will become “LA’s Central Park”. Personally, I think trying to make something “our city’s [insert landmark from another city]” is a bad idea, because it sets us up to try to imitate the features of another city and ignore local context. If Grand Park becomes truly grand, there will be no need to promote it by invoking the image of another city. To their credit, the people running the park have done well at programming events and drawing interest in the park.

Their job would be much easier if the land uses surrounding the park contributed a steady stream of passers-by, people for whom the park was a pleasant way between destinations, not a destination unto itself. This is pretty much straight out of Jane Jacobs writing about Rittenhouse Square in Philadelphia – and wouldn’t you know it, Rittenhouse Square’s 8 acres are not a bad comparison for Grand Park’s 12 acres, much better than Central Park’s 840 acre sprawl.

This means that over time, we need to encourage a greater mix of land uses around the park. There are three blocks between 2nd and 1st, from Grand to Broadway that are currently pretty empty. One is a vacant lot that is slated to become a new courthouse, one is a mishmash of parking lots, and one is a steel-frame parking garage that looks like it had no business surviving both Sylmar and Northridge. The first is zoned PF, the other two commercial. After Regional Connector is complete, there will be subway stops at 2nd/Hope and 2nd/Broadway, in addition to the existing Civic Center stop at 1st/Hill.

This is going to create market pressure to redevelop the lots. The parking lots should be upzoned to allow residential, commercial, and retail, with no parking minimums. LA Curbed reports that the GSA is hoping to find a developer to build a new office building next to the new courthouse. Realistically, the downtown office market is already flooded with vacant space. Why not allow residential, for which there is a big demand downtown, to be built here as well? This, along with other proposed developments in the area, will help pull the downtown building boom towards Grand Park.

The government buildings surrounding Grand Park should not be doomed for no reason other than trying to satisfy these urban design goals. Over time, agencies will likely decide to build new, modern facilities and at that time the parcels will become available for reuse or redevelopment. For example, when the new courthouse at 1st/Broadway is complete, the existing courthouse on Temple between Spring and Broadway can be redeveloped. Conveniently, LA Downtown News has a good look at this issue today.

Graffiti Pit

There’s currently one vacant parcel fronting Grand Park – the shattered remains of a state government building that was terminally wounded by the Sylmar earthquake, colloquially known as the graffiti pit. For reasons I cannot comprehend, the powers that be have decided that solution for this lot is More Open Space – this, despite the fact that the lot already borders Grand Park and City Hall Park. The last thing we need here is more green space.

Before you jump on me, I would implore you to think about how parks work. If that’s not enough, reread the parks chapter of Jane Jacobs. In every article I’ve linked to above, parks are “venerated in an amazingly uncritical fashion”, as she put it. Practically no attention is paid to the land uses around the park that will actually determine if the park succeeds.

A parcel that is bordered by two parks, LA City Hall, the LA County Law Library, and the LA Times should not be a park. It would seem to be a strange use of limited public funds to build yet more open space here. Instead, why not demo the graffiti pit and mitigate any environmental hazards, and then auction off the lot (or lots) to the highest bidders, as I suggested in my post on the 101 in the area? Given current market conditions, residential is probably the most viable use, though this lot is a little bit further from the active areas of downtown and Little Tokyo, which would reduce the desirability.

Unfortunately, we may too far down the open space path to change plans now. Because the virtue of open space is accepted as self-evident, people tend to look askance when you say that a park is a bad idea, and once the park is built, it is very difficult to go back. Nevertheless, I’m still going to try. We really don’t need another park here.

Park 101

To the north of Grand Park, Temple is lined with government buildings on both sides, along with the Cathedral of Our Lady of the Angels. To the west of Figueroa, GH Palmer is building one of its Italian-series buildings, the Da Vinci. North of Temple is the 101 freeway trench, about which I’ve previously written in the context of rationalizing the ramps and improving the street grid. Now let’s look at the Park 101 proposal, which in addition to reconfiguring the ramps would build a deck over the freeway trench with new parks.

Obviously, I prefer my ramp configuration. I’m not sure exactly what Park 101 is proposing, since the “Alternative A” shown in the phasing video looks different than the “Preferred Concept” in the study. But any concept is going to require further study anyway, and the most important thing is to get the ball rolling on a rationalization of the ramps that includes getting rid of the loop ramps that chew up an entire city block. That sets the stage for some selling some property that can help pay for improvements. Park 101 overplans the type of development for my liking; as I’ve said before, we should let the market decide the best use.

Principles for Freeway Cap Parks

To my surprise, the Park 101 Study makes only passing reference to Boston, in the context of increasing property values from the Big Dig. I lived in Boston during the opening of the parks that replaced the 93 freeway elevated structure after the Big Dig tunnels were complete, and there are many lessons to learn about linear parks above freeways from that project:

  • The park has to end somewhere, and that location is likely to be unpleasant because it is going to be subject to freeway noise and fumes. No one really wants to hang out at Portal Park. This suggests that the ends of the park should terminate at a building, not a freeway portal. Clearly, in the case of Portal Park, there’s an extenuating circumstance – the desire to provide a view of the bridge – but that’s not the case with the 101.
  • Don’t overplan the land uses. It is now almost ten years since the 93 freeway elevated structure was demolished, and precisely one of the designated parcels has been developed – a mixed use block between Causeway and North Washington. On all the remaining parcels, viable development plans have been repeatedly rejected, while the preferred plans have proven untenable.
  • Don’t hold the park corridor sacred. In Boston, fanatical NIMBYism has resulted in demands that new development not even cast shadows on the park, which makes it practically impossible to capitalize on the increased land values on the corridor.
  • The development is just as important as the open space. The parts of the Central Artery corridor that work well – the North End Parks, the fountain by the aquarium – have strong generators of interest on both sides. The weaker parts – from High St to Congress St – have weak generators on the east side (because there is only one block to a wide expanse of water) and single-use generators on the west side (offices). When the Big Dig started in the 80s, the environmental reviewers arbitrarily decided that 75% of the corridor should be parks because, well, because MOAR OPEN SPACE. Other architects and planners submitted proposals that the corridor should become more like a series of Copley Squares, bounded by development on all sides. In retrospect, these proposals would have made the parks better.

Now, there’s actually another facility in Boston that’s just as instructive: the Massachusetts Turnpike between South Station and Kenmore Square. Like the 101, the Mass Pike is trenched just below street level  along this corridor, and the city would like to cap the freeway with development and parks. Unfortunately, since the construction of Copley Place in 1983, no progress has been made. The Fenway Center might start construction next year, but don’t hold your breath – the Columbus Center actually started construction in 2008, but then withered. A proposed overbuild at South Station seems moribund as well.

The take away here is that air rights have negative value relative to regular vacant lots, due to the need for unusual structural designs and restricted work hours. If there are benefits to the city at large, this may be a rare case where I would make an exception about giving subsidies to developers.

We should also realize that for cap parks design is restricted by structure depth. This restricts the types of landscaping and park features that can be installed. Also, since you’re on a bridge, at some point you’ll probably have to rip everything out to rebuild the structure.

Finally, if you cap a freeway over a long enough distance, it’s functionally a tunnel, which means you need to provide expensive things like tunnel ventilation (far more costly for freeways than for transit), emergency egress points, fire standpipes, and so on. Therefore, to be cost effective, we should keep the freeway cap sections short enough that they don’t trigger tunnel reviews.

Note that as is often the case with urban design goals, sometimes there is synergy between goals, and sometimes goals are in competition. There are trade-offs to be made. For example, the desire to terminate the park with a building is in conflict with the fact that air rights have negative value. The desire to connect the city to the greatest extent possible is in conflict with trying to keep the cap sections short. These trade-offs can be a question of how much money we want to spend. It’s easy to say we should have more freeway caps, but recognize that public funds are not unlimited. Every dollar we spend here is a dollar we can’t spend on improvements somewhere else.

Alameda to Broadway

The need for a better connection between Union Station and downtown is the most acute between Alameda and Broadway, and it’s no coincidence that in this stretch Park 101 makes the most sense. Logically, this is also proposed to be the first phase of the project.

With the principles outlined above in mind, I think we can get the benefits of Park 101 without capping as much of the freeway or spending as much money. I agree with the Park 101 study that the logical first piece of the cap is the block between Los Angeles and Main. That suggests that the blocks to the north and south should be covered with air rights developments. In the interest of reducing tunnel ventilation and egress costs, I would consider the leaving the center portion of the block open to the air, especially on the large block between Alameda and Los Angeles where the freeway is abutted by onramps that make overbuild difficult anyway.

Note that while public subsidies might be required to induce air rights development on these parcels, the public contribution would hopefully be less than what would be needed to build the cap park. The air rights development would also be beneficial because it would create tax-paying properties and generate more users for the cap parks. More users close to the parks means more successful parks.

With the block between Main and Spring used for air rights development, it’s logical for the next block to the north to be another cap park, between Spring and Broadway. I’ve updated the crappy MS Paint graphic from my post on the 101 to show this concept. Click to enlarge.


Broadway to Grand

As you can see from the graphic, I didn’t do much to cap the freeway between Broadway and Grand, because the value of doing so is lower in this area. Between Alameda and Broadway, the 101 is spanned by 5 bridges with spacing between 350 and 550 feet. It’s over 1,200 feet from Broadway to Grand, with no side streets. In addition, this area is bounded by the Cathedral of Our Lady of the Angels and the Cortines School, both of which have logically turned their backs to the freeway.

With no side streets and little prospect of redevelopment on the abutting properties, there will be very few generators of park users for this quarter-mile stretch. Therefore, in this area I think it makes sense to terminate the park with an air rights building between Broadway and Hill. This building could provide a way to bridge the grade difference between Broadway and Hill to help integrate Hill into the street network.

If anything is to be done at Grand, I’d favor an air rights building on both sides of the street, which would reconnect the street façade from Temple to Chavez.

Alameda to LA River

In this area, I disagree with the Park 101 approach. This area is industrial, and there are overhead transportation facilities (the Gold Line and the El Monte Busway). If the Union Station run through tracks and the CAHSR project are constructed, there will be even more overhead transportation facilities. Those facilities are noisy, and the railroad tracks have sharp curves, which makes them noisier. It’s not going to be very pleasant to hang out underneath these bridges, and not many people are going to want to live or work in expensive high-rises adjacent to them.

In this area, Park 101 would also require taking a large amount of property by eminent domain. Progressives seem to have this weird MO where they worry about the loss of industrial and manufacturing jobs in cities in theory, but promote plans that eliminate those jobs in practice (see the Cornfield for example). Now, maybe industry won’t be the best use of this land when Regional Connector is complete and Little Tokyo and the Arts District keep growing, but that can be addressed by upzoning and letting property owners decide what to do. That puts money into city coffers rather than draining them.

For now, this area is a functioning industrial zone, so I think we should let it be. I put in one air rights development on the east side of Alameda to help reconnect the street façade with Union Station.

Main to Spring Option

As another option, I would consider making the block between Main and Spring a park instead of air rights development. This would create a three-block long park between Aliso and Arcadia from Los Angeles to Broadway. With development on Aliso and Arcadia, and air rights development to terminate the view at Broadway and Los Angeles, this would work pretty well too. It would cost a little more in terms of structure and ventilation. Click to enlarge.


Freeway Widening

The Park 101 Study assumes that the 101 would be widened by at least one lane. The conceptual section on page 45 appears to show a clear span of about 100’ on the 101 north and about 85’ on the 101 south. In contrast, most of what I’ve shown assumes a clear span of about 65’-80’. This is a big difference, because the costs do not scale linearly. Long spans require deeper structures and are considerably more costly; this is the reason that air rights have negative relative value.

District 7 may not want to hear it, but the 101 is wide enough here. Much of the congestion northbound is spilling back from the merge at the Four-Level, which means unless they’re planning to build a fifth lane all the way to the Hollywood Split, widening here won’t do too much. Southbound, the congestion builds back from the East LA Interchange and is related to merging, weaving, and capacity issues on the 60 east and the 5 south. Again, those issues are not going away anytime soon. Personally, I wouldn’t feel too bad about locking the 101 into its current number of through lanes here, and this isn’t even an anti-freeway blog.


Both of these options create considerably less open space than Park 101, but I think the open space created would be more valuable. These options would also allow more development, which generates more revenue for the city. I don’t think the area is at a loss for open space; Grand Park is close and the Cornfield and Elysian Park aren’t too far to the north. I think these options would be more affordable, which means they could be implemented sooner and would have less of an impact on our ability to improve parks elsewhere in the city.

No one should interpret this as an attack on the Park 101 concept; I’m sure a lot of work has gone into the project. The point here is to realize that there are many options beyond just capping the freeway with parks, and we should look at a wide range of alternatives and realize the trade-offs between them.

From 2nd to Union

That about wraps it up for my look at this area for the time being. If I could emphasize one point above all else, it would be the thing that makes a park great is the city around it. Planning in this area needs to start with that fact as the central premise.

The 101 – San Bernardino Split to the Four-Level

In a previous post, I provided some setup for studying the area between 2nd and Union Station. In this post, let’s look at the 101. In another post, I set some ground rules for improving urban freeways, the main gist being that freeway projects and urban improvement are not necessarily mutually exclusive goals. So let’s see those principles in use on the 101.

There’s a lot of attention focused on the area between Union Station and 2nd St lately, and why not? With the development boom downtown, the popularity of Little Tokyo, Grand Park, and transit improvements all over the place, there’s a lot to be excited about. Slicing through the area, first west by north, then northwest, is the iconic 101 freeway – symbol of LA freeways, of LA traffic, of LA growth and sprawl, of LA in general. The Four-Level Interchange even appears on book covers and postcards.

The 101 is the prototypical 1950s freeway, showing the lessons that highway engineers learned from their first attempts. The 101 wasn’t even in the same class as freeways like the 110 north of downtown, which was (and is) a disaster of sharp curves and contorted 5 mph ramps. However, the 101 shows typical 1950s flaws, the biggest being interchanges that are too close together. Engineers eventually figured that out too – check out the 210 between the 57 and the 15 for example.

The 101 between the San Bernardino Split and the Four-Level (i.e. from the 10 to the 110) is one of the most congested freeways in the city. I’m writing this at about 10:30pm and I just opened Google Maps and – yep – it’s yellow. It’s also a considerable barrier between Union Station and downtown. So it’s the perfect place to demonstrate these principles. Let’s run through an option for making things better here, from south to north.

Note: you might want to open up Google Earth or another tab to look at how the images below compare to today. The biggest benefits, from an urban form perspective, are on the north side of the freeway between Alameda and Broadway, on Grand on the north side of the freeway, and at Temple and Hope.

San Bernardino Split

This interchange has undergone modifications in the past. There used to be a ramp from the 10 west to the 101 south, which made redundant when the 5 was constructed, because the ramp from the 10 west to the 5 south serves the same movement. This ramp was removed when the El Monte Busway was built. However, the opposite move, from the 101 north to the 10 east, still has a ramp, and it’s just as redundant.

This ramp should be repurposed into an exit from the 101 north to Chavez and an entrance from Chavez to the 10 east. The utility of this interchange will become apparent shortly. Concurrently, the slip ramps to and from Kearney St should be eliminated, removing freeway traffic from local streets in Boyle Heights.  These ramps would also give traffic coming east on Chavez an entrance to the 10 east without going through Boyle Heights.


Mission Interchange

The ramp from the 10 west, to the 10 east, and to the 101 south are relatively benign, so they should be left alone. The ramps from the 101 south to Mission and from Mission to the 101 north are theoretically too close to interchanges to the north. However, they should also be retained, since they provide access to and from industry on the east bank of the river without sending traffic through Boyle Heights. (Issues on the 101 between the 10 and the East LA Interchange will be addressed in a separate post.) Considering the congestion on the 101 north here, you’d be a fool to get on at Mission anyway, and I don’t think many people do so.

Vignes/Garey Interchange

I like to call this style of interchange a “kiss interchange” since the ramp termini look like puckered lips in plan view, making it look like the freeway is kissing the other road. Since they’re cheap to build, these are plunked down all over the place on 50s-era freeways. The ramps at Vignes and Garey are all much too close to the preceding and following interchanges, and they’re redundant anyway, so they should all go. Northbound traffic would get off at the new Chavez ramp I mentioned above or at Alameda; southbound traffic would get off at Los Angeles. Traffic entering northbound should enter further north; traffic entering southbound should enter at Los Angeles or from Mission.


Alameda/Los Angeles Interchange

The ramp from the 101 north to Alameda should be retained and become one of the primary exits to the downtown area. It takes up little ROW, provides access to Alameda and Union Station, and provides access to other north-south arterials via Arcadia.

The ramp from the 101 south to Los Angeles should be retained and reconfigured to also provide access to Aliso eastbound. Access to Los Angeles northbound is not critical because there is a left from Aliso to Alameda northbound. This allows this ramp to serve the functions of the eliminated Garey St offramp.

The ramp from Los Angeles to the 101 south should be retained and lefts should be permitted from Los Angeles southbound onto this ramp. This ramp becomes one of the main southbound entrance points and assumes the functions of the eliminated Garey St onramp.

The ramp from Los Angeles and Alameda to the 101 north takes up an entire city block, directly across from Union Station. This ramp should be configured as a slip ramp from the intersection of Aliso and Alameda onto the 101 north.


Spring/Broadway Interchange

The ramp from the 101 south to Broadway is way too close to the onramp from the Four-Level. It should be eliminated and replaced by an extension of Aliso north to Grand and improvements further north. Due to the crazy grade changes in this area, it’s not possible to have the extension of Aliso intersect Hill – it’s too high up.

The ramps from the 101 north to Spring and from Broadway to the 101 north take up an entire city block, have terrible geometry, and are too close to adjacent interchanges. These ramps? Gone. Arcadia should then be extended north to Grand. Again, the grade differences make it impossible for the extension of Arcadia to intersect Hill.


Grand/Hope Interchange

It would be nice to turn the loop ramp from the 101 north to Grand into a slip ramp on the south side of Grand, but the severity of the topography in that area would push the ramp too far south, close to the Alameda onramp. Instead, the ramp should duck under the onramps  and in a slightly larger loop and terminate at Grand where the onramps currently start. The onramps to the 101 north should be moved to the west and square up with the extension of Arcadia. I considered sending the offramp to turn right onto Bunker Hill and come out at the intersection with Chavez, but that would add a ton of traffic turning right from Bunker Hill to Chavez and then Chavez to Grand, so I nixed that. I also thought about sending this ramp to the left under the 101 to come out at the intersection of Hope and Temple, where the ramp from the 101 south currently ends, but I don’t think that grading would work.

The 101 south ramp that currently goes to the intersection of Temple and Hope should be reconfigured to square up with the extension of Aliso, and Hope should be extended to that intersection. The offramp to Temple from the Four-Level ramp that heads to the 101 south should be reconfigured to square up with the intersection of Hope and Temple (taking the place of the current ramp from the 101 south).


Another option would be to get rid of the fork of the onramp from Grand that goes to the Four-Level and just let that traffic use Figueroa to the 110. The offramp to Temple and Hope from the Four-Level ramp could be eliminated too, and replaced by a better configuration of the offramp from the 110 south to Figueroa. However, I decided against this option because the ramp from Figueroa to the 110 north and from the 110 south to Figueroa should probably be eliminated as part of rationalizing the ramps on the 110 (more on that another time).

Four-Level Interchange

I’m a little gunshy about going after the Four-Level. After all, it’s basically where freeway engineering was born – the  first high-speed semi-direct interchange ever. But LA ain’t a museum, just ask the people in Beverly Hills buying $10m teardowns. Nostalgia is for chumps. The Four-Level was fully opened in 1953, before the 10 and the 5 were complete. At that time, it was necessary to provide all the movements. But at this point all four movements to the 101 south and from the 101 north may be redundant.

I started looking at options for eliminating and reconfiguring ramps at the Four-Level, but you know what? Any changes to the Four-Level are only about eliminating short weaving distances and redundant ramps on the 101 and the 110. They’re not about improving the streets downtown for pedestrians or cyclists, and they’re not about reducing ROW footprints and opening up land for redevelopment. Now, maybe it’s worth doing some improvements at the Four-Level, but they’re a separate issue from what I’m trying to get with this series of posts, which is better connections from the Union Station area to downtown. So let’s leave the Four-Level alone for the time being.

Other Options Abound

This is, of course, just one option, and there are plenty of other ways you could configure things. Come up with your own, and let’s get to work on convincing the city and Caltrans to do an analysis.

Now We Have Real Estate to Work With

The land vacated by these ramps should be redeveloped. And instead of doing the normal deal where we have a design competition, give the developer unreasonable subsidies, and end up with vacant lots for years, how ‘bout this: zone the land for any residential or commercial use (and industrial for the piece on Commercial St), no parking minimums, no tax abatements or subsidies, no FAR/height limits, no nothing. We just auction it off to the highest bidder with two conditions: no surface parking, and you gotta build something there within 5 years. We should also break up some of the larger blocks into a few different parcels and auction them off separately. You want to buy the whole block, ok, but you have to win the bid for each piece.  It’ll be a fun experiment.

This project really is an all-around win. It opens up new land for urban development, which unlike any of the proposed parks in the area, actually helps connect Union Station and downtown. It fixes dangerous conditions on the freeway that waste capacity. It makes things better for pedestrians and bikes by getting rid of loop ramps and improving the street grid. And the ROW sale would help fund the project. What’s not to like?

Note: you used to be able to import Google Earth images and topographic data into AutoCAD, which was pretty sweet, because you could draw real engineering stuff and then export it back to Google Earth. As part of Google’s continuing campaign to make its products worse, this feature is no longer available. This leaves several crappy options for trying to share this kind of work:

  • Find the best aerial you can get in AutoCAD (often way out of date) and work with that (but then it’s a static picture other people can’t look at in Google Earth).
  • Draw with polygons in Google Earth and hope that the geometry isn’t insane.
  • Draw it in SketchUp, which is basically like trying to cut down a tree with a jackhammer: it’s not that it’s a bad tool, but it’s clearly not designed for this type of work. I could write an entire post on how bad SketchUp is for civil engineering, if I was looking for exercises in futility.

Therefore, for now, I’ve gone for the fast route with questionable accuracy – drawing Google Earth polygons. I’m going to try to update this using SketchUp to verify the geometry and give others the ability to edit, but I’m not making any promises.

Contact me if you want the Google Earth shape files.


At Kenny Easwaran’s suggestion, here is an image of the whole corridor. Click to enlarge. Again, apologies for the low quality, but Google Earth and MS Paint is the fastest way to get it done.

101-all2Going north on the 101, after First St, your exits would be Chavez, Alameda, Grand and the Four-Level. Going south on the 101, after the Four-Level, your exits would be Grand, Los Angeles, and Mission. Your entrances to the 101 north would be Mission, Alameda, and Grand; to the 101 south, Temple/Hope, Los Angeles, and Mission.

Principles for Freeway Improvements

Historically, freeway capacity improvements have often been made without putting too much thought into trying to get the most out of existing facilities. Problem: congestion. Solution: MOAR LANES. I think this is for the same reason you see streetcar projects popping up all over the place these days – other people’s money. For a long time, the federal government paid for 90% of freeway construction costs, so states didn’t really care how they spent the money. This has led to maintenance backlogs for states that built more than they could maintain, but that’s a separate problem.

Some readers are no doubt of the opinion that in the long run we should get rid of urban freeways. Let’s leave that debate aside for the moment and note that freeway removals are long-term projects and can be expensive, while the things I’m talking about here are short-term things we can do for cheap.

So, smarter freeway projects. Let’s assume you’ve already taken things like competing against transit and the arguments against new freeway capacity into consideration.  Here’s what you need to pay attention to when you design your project.

Make Things Better for Pedestrians and Bikes

At the end of freeway ramps, cars transition between an exclusive, high-speed facility and local streets, with lower speeds and competing uses. This means ramps are therefore prime locations for terrible incidents with drivers striking pedestrians and bikes. Therefore, it’s important for off-ramps to send a strong message to drivers: you’re not on the freeway anymore, and for on-ramps to send a similar message: you’re not on the freeway yet.

The best way to do this is with design features that force drivers to slow down or stop at the ramp terminus. A hard stop forces you to reset your expectations. To that end, here’s a quick assessment of how different types of interchanges perform:

  • Cloverleaf: probably the worst, since all turns to and from the freeway are free-flowing. Drivers coming off the freeway are likely to keep going too fast, while drivers entering the freeway are likely to accelerate into the ramp, increasing the chance of right-hooking a pedestrian or bicyclist. In addition, the ramp geometry results in long skewed crosswalks or the need to try to force pedestrians out of their way to a shorter crossing. If you try to cross a ramp like this with any regularity, you know how scary they can be.


Cloverleaf: the 710 at Willow. Note long & skewed crosswalks, large ROW needs, and weaving movements on freeway.

  • Partial cloverleaf: a little better, since it probably introduces a traffic light, but still has some free rights. A four-ramp partial cloverleaf is better than a six-ramp.


Six-ramp partial cloverleaf: the 91 at Lakewood. Less ROW and no weaving on the freeway, but still some free rights. In the SW quadrant, we have a crosswalk that forces pedestrians to take a circuitous path. In the SE quadrant, we have a skewed crosswalk.


Four-ramp partial cloverleaf: the 405 at Hawthorne. Note that the interchange ROW is tight to the freeway. The ramps intersect Hawthorne at a tight right angle, and this location has no right on red. This forces drivers to stop and reset.

  • Single-point urban interchange (SPUI) and diverging diamond: these interchanges were designed to move as much traffic as quickly as possible. Pedestrian and bike facilities are an afterthought, and to be blunt, they suck. SPUIs and diverging diamonds might be ok in a suburban or rural context, but they don’t belong in cities.


SPUI: the 10 at Archibald. The ROW is pretty tight, but the pedestrian crossings are skewed, and drivers are encouraged to speed by free rights.

  • Tight diamond: in this design, the ramps intersect the street in essentially the same configuration as a regular intersection. All traffic, including right turns, must stop before proceeding. This is the safest design for bicyclists and pedestrians, so when urban freeways are reconfigured, this is the design that should be used. Note that a properly designed partial cloverleaf can do this job just as well.


Tight diamond: the 405 at Culver. Minimal ROW impact, and the intersection of the ramps with Culver is like a normal intersection.

Reduce the ROW Impact of the Freeway

Freeways make gaps in the urban fabric. In newer areas of development that have grown up around freeways, it’s not that big of an issue, but in cities, freeways can be real barriers. Many older freeways were designed with a callous disregard for context, so any reconstruction projects should try to fix these problems.

Happily, there’s a lot of synergy between the goal of making things better for pedestrians and bicyclists and the goal of reducing the ROW impact. The interchange designs that minimize ROW impacts are also the ones that are best for pedestrians and bicyclists. If you’re in a dense urban area, there’s really no reason to ever build a loop ramp. The marginal benefit to traffic is just not worth it. The only exception to this is where the freeway crosses the intersecting road at a skew, like in the four-ramp partial cloverleaf shown above.

Make the Most of Existing Capacity

Adding lanes is the “dumb” solution, because it requires the least amount of thought. You don’t have to do any critical thinking about what’s causing the congestion. But adding lanes is also usually the costliest solution, and the most disruptive to the city, so adding lanes should be the improvement of last resort. That’s not to say it never makes sense. For example, where the 5 drops from five lanes to three lanes in La Mirada, it’s pretty clear that the inconsistent number of lanes is the source of congestion. (Note that theoretically, you could fix this by adding lanes in LA County or removing lanes in Orange County. If we want to do the latter, that’s fine, but we need to explain how we will accommodate the travel demand.)

However, in many cases, congestion is being caused by deficient design on the existing freeway. These issues should always be analyzed and addressed before adding lanes. The most common deficient design feature is inadequate weaving distance. This is a major source of congestion on many older urban freeways, which were built when the understanding of freeways was primitive, and have entrance and exit ramps placed too close together. Some examples of this in Los Angeles are the 10 between Western and the East LA interchange, the 110 between Florence and Adams, the 101 from the East LA interchange to the Hollywood Split, the 405 between Inglewood and the 110, and the horrible weaves on the 110 between the 10 and the Downtown exit, and between 3rd St and the Four-Level.

There are three options for addressing weaving problems caused by close interchange spacing:

  • Eliminate some of the on and off ramps to increase interchange spacing. This is the cheapest option, and it may be possible to recoup some costs by selling the old ROW.
  • Add auxiliary lanes or collector-distributor lanes. This is a moderate cost option aimed at easing, but not eliminating the weave.
  • Braid the ramps. This is an expensive solution requiring bridges, and probably ROW.

There are two key questions in choosing an option: how important is it to provide ramps to all these surface streets, and how much money do you want to spend? If you really need access to all the streets, auxiliary or C-D lanes will help. Braided ramps should be reserved for only the heaviest volume locations.

In general, I think removing ramps is underappreciated as a viable option. You help solve your freeway congestion problem. You save money. And you get to remove through traffic from neighborhood streets that probably shouldn’t have had ramps in the first place. If your interchanges are less than a mile apart, odds are you’re dumping freeway traffic into the wrong places anyway. Removing ramps is a way to improve neighborhoods. What’s not to like? We should be removing more ramps.

There’s also some synergy to be had with the previous two goals. Cloverleaf interchanges inherently have short weaving distances between the loops, so they can also cause congestion. They also take up a lot of ROW. They should be replaced with other interchange designs, preferably tight diamonds or, where the freeway is crossing at a skew, a tight partial cloverleaf. The 710 is littered with 1950s-era cloverleaf setups, so when that project goes forward, they should rebuilt in that manner. As a bonus, turning those interchanges into tight diamonds frees up some ROW that can be sold for commercial development or whatever.


In conclusion, freeway reconstruction projects on the older LA freeways should be looking to do the following:

  • Get rid of ramps where interchanges are too close together.
  • Get rid of loop ramps that waste urban space.
  • Square up ramp junctions and get rid of free right turns to make things safer for pedestrians and bicyclists.

We’ll see these principles in action in a new post soon.