Monthly Archives: March 2014

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.


Why You Need Through Running

Through-running usually comes up in the context of New York (ARC vs Alt-G; NJ Transit, LIRR, & potentially MNR all turning back at PSNY; East Side Access not connecting to existing Grand Central) and sometimes Boston (no connection between South Station & North Station).

Well guess what you East Coast pikers, there is a city about to rectify its dead-end downtown terminal – Los Angeles. As is often the case in LA, the plan involves a lot of concrete and aesthetics that would make other cities blanche.

Let’s leave aside the question of whether current Metrolink and Amtrak volumes warrant the run-through tracks at LAUS, and review that particular plan in a future post. For now, let’s explore why through-running is important. This is something that people who know railroad operations would take as self-evident. But most people, whose frame of reference is auto traffic or bus operations, might not understand what dead-end operations mean for a railroad.

Capacity Curves

First, let’s borrow a basic graphic from freeway engineering. This plots traffic speed (x-axis) against traffic volume (y-axis).


On the right end, we have high speeds with little traffic. As you add more cars, increasing traffic flow,  the speeds get lower, which is what you’d expect. Then at some point you reach a maximum possible throughput. Add more cars to the freeway, and traffic volume actually starts to go down. This is a little counterintuitive for some people – when the freeway is totally full of cars, the traffic volume is very low. It makes sense if you think it through, though – if the freeway is totally gridlocked and no one is moving, the volume of cars passing a fixed point is zero because, well, no one is moving.

That curve is the reason every freeway on-ramp in Los Angeles has ramp metering. By regulating the flow of cars onto the freeway, you hope to stay on the right hand side of the curve, maximizing throughput. Even if average volume is below maximum throughput, a small burst of cars entering all at the same time can push you onto the left side of the curve. Once you go over the top onto the left side of the curve, you’re doomed to have congestion and unstable traffic flow, which won’t clear until after rush hour when the volume of cars trying to enter the freeway drops way off. (If your state DOT doesn’t have ramp meters and they want to widen freeways, well. . .)


Ok, back to trains. Some basic about rail operations. Trains move proceed along the tracks as directed by the signal system. Since we don’t ever want to have opposing trains heading towards each other on the same track, the signal system is set up to enforce the direction of traffic between interlockings. Interlockings are locations on the track where switches allow trains to move from one track to another.


So, in the graphic above, there is a train moving east between B and C. Traffic on this section is to the east. There’s a train waiting to go westbound. The dispatcher can request a route for the westbound train, but that route won’t clear (be given a green signal) until the eastbound train clears the interlocking at C and the signal system checks that there are no other trains between B and C, and no conflicting routes requested.

Even in this simple case, the dispatcher has to make a decision. When the route is cleared for a westbound train, the following eastbound train (between A and B) will have to wait at B. If there are a lot of eastbound trains, it’s possible that they’ll start to get backed up at B. And just like that, you’re on the wrong side of the capacity curve, and all your trains are delayed. If your station throats are operating near maximum throughput – like, say, the Hudson River Tunnels entering Penn Station – it doesn’t take much of a delay to make that happen.

Smooth Operator

That’s a simple case with an obvious capacity constraint in the single-track section. Now, let’s consider a more complex case. Suppose that we have a terminal station like Penn Station New York, where the tracks run through, and that the service is planned with through-running.


This is a really easy system to dispatch. Eastbound and westbound trains never conflict with each other. The dispatcher never has to change the direction of traffic. We could even set up the signal system entering the station to automatically throw the switch to whichever platform track is clear. All the dispatcher has to do is set routes for trains leaving the station, in the proper scheduled order.

Rough Sailing

Now take the same station and have service from each side operated by different agencies, with no through-running; each agency treats the station like a stub-ended terminal.


Consider the red trains entering eastbound. Should the dispatcher send the westbound train out in front of the first eastbound train, hoping it doesn’t cause delays to tumble back? Or should the dispatcher wait for the first eastbound train to enter, and then send the westbound train? What if the westbound train is running a minute or two late? The platform needs to be made available for following trains to enter the station. Is it better to delay that one westbound train a minute or two than to risk delays to eastbound trains? Even in this simple terminal, the dispatcher faces tough decisions, and if train volumes are high, they must be made every few minutes.

Consider a more complex stub-ended terminal like LA Union Station.


The dispatcher faces many difficult choices. In addition to deciding which trains to prioritize, the dispatcher must decide the track on which to berth each train. Poor decisions can come back to haunt you. For example, suppose a train is entering from the Ventura Line and is berthed on Track 13. If that train’s next trip is to the Antelope Valley Line, it will have to cross the entire terminal interlocking on its way out. During that time, no other trains will be able to enter or leave the station. However, if that train is heading out to the Orange County Line, putting it on Track 2 when it comes in might be a good decision, because it won’t interfere with any other moves on the way out!


The situation gets worse if, in addition to the two stub-ended operations, we have some through trains, like Amtrak service at Penn Station. Now, the choice to delay the westbound red train could cause delays to a westbound through train, which could tumble back to the operator of the blue trains to and from the east.

If the services are all being operated by different agencies, it’s inevitable that one service is going to come out on the top of the heap – probably, whichever service is provided by the operator that dispatches the terminal. That employee has an incentive to try to keep their trains on time, meaning they might dispatch their trains first even if the overall result is more delay on the network. Consider, for example, South Station in Boston, where Amtrak has dispatch rights. How much is Amtrak going to worry about the on-time performance of the Worcester Line if its trains are late?

Of course, all of this can be ameliorated by good scheduling, which includes a plan for assigning trains to the right track. But even in that case, service disruptions are harder to deal with and have a greater chance of getting out of control.

Don’t Dwell On It

This analysis hasn’t even touched on another issue, which is the platform dwell time required to switch train directions. In the US, this is generally a minimum of 10 minutes, enough time for passengers to alight, the engineer to switch ends and do the FRA-required brake test, and new passengers to board.

I’ve heard that in other countries, they turn trains faster. Even so, it’s obviously more efficient if the engineer doesn’t have to switch ends of the train. You can avoid that if you have a new crew waiting to board the train at the station, and in fact, this is how LACMTA runs things at 7th/Flower on the Blue and Expo Lines. The downside is increased labor costs, because you always have at least one crew just waiting around the terminal.

Through-running eliminates these problems and reduces dwell time, which increases the capacity of the terminal. This is one of the reasons why a place like Shinjuku Station can handle 750,000 passengers per day on 16 platform tracks while places like Boston South Station are planning expansions because they’re having trouble handling 45,000 passengers (6% of the ridership) on 13 platform tracks. (After glancing at track maps of Shinjuku, I also suspect that they keep things running smoothly by blocking off the terminal into operating segments, rather than sending trains all the way across a massive terminal interlocking like US operators are wont to do, but more on that another time.)

Run Through If You Can

So that’s a simple summary of why you need through-running. US operations don’t need more tracks; they need better operations. As Alon Levy says, organization before electronics before concrete.

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.

Neil Young, Environmentalism, and LA

Just a quick post; working on some longer things, one of which will hopefully be ready later this week.

I’m finishing up reading Neil Young’s book, Waging Heavy Peace. Not exactly your normal land use and transpo fare, but there are interesting lessons everywhere. The book, like Young’s music, does what it wants and is sort of all over the place, but there’s a couple things that stick out in my mind.

First, Young was of course part of the hippie dream, and caring about the environment was a huge part of that movement. It’s something that’s still a huge part of his character; for example, the home page on his website talks about smog in China and the need to reduce greenhouse gas emissions. However, like I tweeted about Randal O’Toole’s backstory (fighting to stop the USFS from clear cutting national forests), the relationship between environmentalism and cities has always been uneasy. US environmentalism is not just about preserving nature, but about the right to be among nature and enjoy it on one’s own terms. Young’s automobile project – converting a 1959 Lincoln Continental to run on biomass – is typical of that view: that you should be able to have your cake and eat it too. That’s not always the case. Dense cities, which inherently require individuals to surrender some connection with nature and share space with others, are not a natural complement to that type of environmentalism.

That brings me to the second notable thing in Young’s book – the City of Los Angeles. It isn’t explicit, but if you pay attention it’s there. Young moved to Los Angeles in 1966 and formed Buffalo Springfield, playing at clubs on the Sunset Strip and trying to get exposure to the Hollywood-based music industry. The band members, along with many of their musical contemporaries, lived in rented houses in Laurel Canyon and Topanga Canyon.

Stop and think about that for a second. A 21-year old with no money moved from Canada to Los Angeles. . . and rented in Laurel Canyon! And he didn’t even have a green card until 1970! That’s what cities are supposed to be about: providing that type of opportunity for anyone. It only worked because Young and many like him could afford to be near the strip and Hollywood, where matching in the music industry was taking place. Affordable housing in the IE wouldn’t have helped. To provide opportunity for all, the city has to be affordable for all. And that’s the biggest challenge facing LA today.