Do Pedestrian Scrambles Make Sense?

Pedestrian scrambles have enjoyed some increased popularity lately, popping up at Hollywood & Highland in LA and Brand & Harvard by the Americana in Glendale. This arrangement is also known as a Barnes dance after the traffic engineer who promoted it. Note that diagonal crossing is permitted at these locations.

There are several advantages to the scramble:

  • Pedestrians have their own phase, with no traffic movements, which decreases the likelihood of drivers crashing into pedestrians.
  • People wishing to cross both streets can do so in one crosswalk phase.
  • There are no pedestrians during the auto phases, which increases the throughput of the turning movements for cars.

However, there are also several disadvantages to the scramble:

  • If the scramble is added at the expense of left turn arrows, the capacity of left turn movements will be negatively impacted.
  • If the scramble is added but the other phases of the light cannot be shortened (i.e. the walk movement was not the constraining factor on phase length), the cycle time will increase.
  • Vehicular capacity in general may be reduced, simply by reducing the percentage of green time in the cycle (g/C ratio).
  • Pedestrians only wishing to cross one street may see an increased delay.

My hunch is that, in general, pedestrian scrambles only make sense where pedestrian volumes are very high. Otherwise, the increased pedestrian wait time (which encourages jaywalking) and reduced vehicular capacity may offset the benefits. Note that even the world-famous scramble in Shibuya only allows the shorter of the two diagonal crossings.

The reason scrambles make sense when pedestrian volumes are very high is that large pedestrian flows will crush vehicular turning capacity, especially for right turns, which rarely have their own turn arrow. When pedestrian volumes are low or moderate, all pedestrians can step off the curb at more or less the same time, leaving the tail end of the green cycle for right turns. When there are huge numbers of pedestrians, though, pedestrian flow will continue right until the end of the cycle, and almost no traffic can turn. This leads to dangerous turns by frustrated drivers and more congestion on city streets. Anyone who has spent time in Manhattan has probably noticed congestion fomented by vehicles stuck trying to turn – and nearly been clipped by a driver turning on their heels.

The scramble solves this by eliminating the conflict for turning vehicles; despite the lost green time in the cycle, this may improve vehicular capacity by preventing gridlock from forming. This is not the only way to address turning vehicle congestion; some traffic lights in downtown LA (east side of Figueroa at 6th and west side of Flower at Wilshire, for example) have a lagging right turn arrow that comes after the pedestrian interval clocks out.

In a future post, we’ll dive a little more into the weeds to compare these options.

Parcel Taxes are Better Than Impact Fees

A short note on housing development impact fees. These fees are popular with California cities for a variety of civic improvements, like parks and affordable housing. They owe their popularity to two facts: one, thanks to Prop 13, cities have the ability to levy them more easily than property or sales taxes, and two, the public sees the tax as falling on Big Bad Developers™ and on people who don’t even live in the city yet.

Unfortunately, because they fall on such a small portion of the city’s land and on such a small number of housing units, impact fees are a poor way to fund civic improvements, and have undesirable externalities. On the first count, the fees will never generate very much money relative to the city’s budget and needs. On the second count, because the fees will be set relatively high compared to the value of the housing in an attempt to at least get some improvements out of them, they will drive up the cost of housing. In the case of affordable housing impact fees, the resulting increase in rents makes impact fees somewhat self-defeating as method of achieving the goal.
The unavoidable problem of impact fees is that unless we are developing a large greenfield master plan housing subdivision in a new suburb, they inevitably place a heavy burden on a small portion of the housing and land.

Consider trying to build 10,000 affordable housing units in LA County – a small number relative to the total number of housing units in the county, which is over 3.5 million. Even when development in the county was occurring at a relatively quick pace in the 1980s, at 75,000 new units per year, the cost per unit would be huge. At an affordable unit cost of $300,000, each of the 75,000 new units would be saddled an impact fee of $40,000; at 4% for 30 years, this is higher mortgage costs of about $200/month. There’s simply no way this fee can be assessed without depressing new housing construction.

On the other hand, if the fee is assessed on all 3.5 million housing units in LA County, the assessment will be about $850 per unit, or about $4/month for 30 years. This will have practically no impact on the cost of housing. Thus, it may even be possible to increase the affordable goal.

Lastly, consider a tax on assessed value, also known as a property tax. The current assessed value of LA County is roughly $1.264 trillion dollars. The tax to fund the affordable units would be about $1 per $100,000 of assessed value, reducing the burden on each unit even further.

Simply put, if we have worthwhile community goals, we should fund them in a way that’s fair and that works. Parcel and property taxes are not as popular, but they are much better, and we should fight to do things that way when we can.

The Money’s in the Infrastructure

This is just a short thought on the economics of transit capital costs and operations, which has been bouncing around in my head in the wake of service reductions at many agencies.

As any transit planner would tell you, reducing service can lead to a vicious cycle, where less frequent and therefore less convenient service causes ridership to drop, which becomes justification for further cuts. This is bad enough in a generic bus system, but at least in that case there’s little capital infrastructure that goes to waste, since most city buses just run on regular streets that are already there.

However, for something like rail transit, it’s truly crazy to cut service (unless you’re forced to by maintenance needs) due to the relative magnitude of capital investment. A brief example shows why.

Consider a 10-mile rail line built at a cost of $150m/mile, a total of $1.5b. Spread out over 30 years at 3%, the cost of construction is about $76m/year. If we run the line for 20 hours a day (4am – midnight) with 6 minutes headways, with reasonable cost per revenue-mile, it costs about $24m/year to run the line. This assumes 320 weekday equivalents, representing slightly reduced service on the weekends. The total cost is about $100m/year, of which capital costs are 75% and operating costs 25%.


Now, let’s impose an austerity plan on the line, reducing service to 16 hours a day (6am – 10pm), cutting frequency in half to 12 minutes, and further reducing weekend service to get weekday equivalents down to 300. The operating cost is reduced by over 60%, but the capital costs cannot be changed. The total cost is about $85m/year, only a 15% reduction from the base plan. As a result, passengers will get much less useful service and some will quit riding the line altogether, further worsening the financial position. And the austerity plan will likely reduce the efficiency of labor and equipment usage, again cutting into the savings.

We can see how illogical this is by considering some simple analogies to driving. Once you have bought a car and committed yourself to monthly auto loan and insurance payments, you can’t cut your costs very much by not driving. In fact, not driving may worsen your position by depriving you of employment. The capital costs are large relative to operating costs.

Likewise, if Caltrans is short on money for maintenance, it would be silly to try to rectify that problem by simply closing one or two lanes on the freeway. No one would ever suggest this because it would be considered intuitively obvious that closing freeway lanes constructed at great capital expense to save a few dollars on maintenance is not in the public interest.

The wrinkle here is that transit agencies often don’t pay for the full cost of capital projects, or don’t account for it out of the same pot of money. In that case, there really should be some mechanism to ensure that adequate operating funds are secured so that the public’s capital investment isn’t wasted. I believe the FTA requires recipients of New Starts funding to demonstrate this in a finance plan, but the enforcement may not be there. The FTA has sometimes demanded that funds be returned when not used for the capital improvements promised – see ARC and Cleveland for examples – so maybe service spans and frequencies should be spelled out in funding agreements as well.

Do Park and Ride Lots Make Sense?

Park and ride lots for transit are common in the US, especially on commuter rail systems and outlying stations of rapid transit systems. Many urbanists do not like park and ride lots, seeing them as a waste of space that could be better used for housing, which would not only provide riders, but reduce car dependence and avoid the capital costs of parking. So, I thought a brief look at the economics of park and ride lots from an agency perspective might be interesting.

Suppose we have a site adjacent to a transit station. We could build a parking lot or garage, and let drivers park for free, in which case a portion of the transit fare is actually covering the cost of parking construction. We could build parking and charge enough for parking to cover the cost of parking construction, so none of the transit fare is subsidizing the parking. Finally, we could build housing, at some density – single-family houses, townhouses, podiums, or hi-rises. In that case, some of the residents would become riders, and the transit agency may be able to collect some profit on the housing.

The analysis below runs the numbers on 8 hypothetical scenarios for a 10 acre transit-adjacent site: free parking lot, $3.00 parking lot, $5.00 parking garage, $10.00 parking garage, single-family subdivision, townhouses, podium-style apartments, and hi-rise development. The assumptions are all laid out in the spreadsheet. Housing profit margin is based on what the National Association of Homebuilders reports. The equivalent zone is what the development would be per City of LA zoning. Transit fare and service cost are per LACMTA data for heavy rail.


As one might expect, free parking loses money for the agency. Since the service cost is greater than the fare, the cost of building the parking is entirely a loss. If the agency can charge a modest amount for parking, in this example $3, the surface lot turns into a little bit of a money-maker. $298k/year is not a huge amount of money, but it’s something, and this option actually performs better financially than the single-family housing or townhouse options.

Due to high capital costs, a parking garage can be either a big winner or a big loser. If the agency can charge $5 for garage parking, the result is a loss of over $8m/year, but if it can charge $10, the result is almost $4m/year in profit, by far the best option. Note, however, that this is dependent on the ability to consistently fill a nearly 1100-space parking garage at $10/day. There are some locations where this will pencil out, towards the edges of the city and some commuter rail stops. (People might pay $10 to park downtown, but then they won’t even bother to ride transit, which is sort of self-defeating from a transportation and land use policy perspective.)

All of the housing options are guaranteed to generate at least some money by virtue of the profit from selling the housing. Obviously, the podium and hi-rise options do best and beat surface parking in nearly any scenario. If you are in a neighborhood where podium or hi-rise development pencils out, you probably don’t want your transit agency to be in the business of building parking garages anyway.

One thing to note here is that the analysis is quite sensitive to the interest rate. This is because the parking options have large up-front costs, while the housing options have large up-front profits. An increase to 5% turns both garage options into big losses, with even a $10/day garage swinging from $3.8m gain to a $1.1m loss. In contrast, the financials of the housing options improve.


Lastly, please note that this is a very rudimentary analysis and does not account for benefits and impacts to other policy goals. For example, a 5445-space parking garage might be a winner for the agency, but if it’s not located close to a freeway, it may cause a lot of neighborhood congestion. Building housing creates the opportunity for more people to live in the city, while building parking only creates the opportunity to live somewhere else and drive. And of course, parking lots and garages create border vacuums and dead zones in the city fabric, which is undesirable.

Bottom line: park and ride lots may make sense in suburban and exurban areas if parking fees are enough to cover the cost of lot construction and help subsidize transit operations. Otherwise, build more housing.

Elsinore Beach

A month ago, I was visiting a friend in downtown Hermosa Beach, and a couple weeks ago I went to dinner in downtown Manhattan Beach. Though the beach cities have a suburban reputation, I’m always struck by just how much density there is in the downtowns – say, within a half mile of the beach.


Further inland you get larger lots of 3500-7500 SF, though many are still developed with two or three small lot size houses that are interesting in their own right, but today I want to focus on the development near the beach.

This is classic LA County development that doesn’t feel dense but is actually has quite a bit of density. Since many people like (or believe they like) suburbs more than cities, development that hits a density of 10k-15k people/sq mi without feeling too urban is extremely useful. The development pattern in this area also provides a ton of small units and small buildings, making it affordable to a many different people. Walkable, ocean breezes and beach access, varied housing stock: so, why don’t we build Hermosa Beach anymore?

The impulsive response is that it’s because there’s nowhere left on the SoCal coast to build it. That’s… mostly true. We’re obviously not going to develop Camp Pendleton, because the Marines need it and it’s nice to have such a large, relatively unspoiled natural coastal area in the otherwise almost unbroken stretch from Imperial Beach to Malibu.

But it’s not entirely true. In fact, Taylor Morrison is currently developing a large (about a quarter of a square mile) site in San Clemente right across the street from the beach. The development will have 330 houses, which will result in a density of about 4k/sq mi, about 25%-30% of the density of Manhattan Beach and Hermosa Beach.


Sure, you say, but that’s southern Orange County. It’s all low density gated community exurbs; they wouldn’t know good design from a hole in the ground. Except… the adjacent census tract is practically an outpost of beach city style development, with a density of 12k/sq mi.


So what gives? Obviously, the zoning: the maximum density is 4.5 dwelling units per acre (du/ac). At that density and what must have been astronomic land costs, all you’re going to get is huge single-family homes, and indeed the cheapest house in the new development is north of $1 million. It kind of makes you wonder what the Coastal Commission was doing not insisting on more density, to make the area more accessible to more Californians.

Beyond that, we don’t have much coastline left in SoCal if you want to build a waterfront city. The Colorado River is too far east, and the Colorado Valley is very hot in the summer. The Salton Sea probably could support some beach city development, but first we really need to figure out an environmental plan to save it. That leaves us with a few scattered waterbodies in the Inland Empire like Canyon Lake (already developed) and Lake Elsinore.

Lake Elsinore isn’t exactly an easy commute to LA or even Orange County, but it is a very pretty spot. Aside from the eponymous lake, the Santa Ana Mountains rise in the background to their crest at over 5,000’ on Santiago Peak. On the north shore of the lake, a small ridge rises, not unlike the beach cities sloping up from the ocean.


Now, the really crazy thing is that while this area is undeveloped, it appears to have been subdivided a really long time ago. It has a ton of small lots and awesome narrow, hillside streets. It’s currently zoned Residential Hillside, which only allows single-family development and has rural type development requirements (30% max lot coverage, 12,000 SF minimum lot, 20’ front & rear setbacks, 5’ & 12’ side setbacks), though you’d likely be able to get variances for existing lots. The lake front itself has its own zone, which allows restaurants and conditional uses for some other commercial development.


Probably because of the zoning and somewhat challenging topography, you can buy land here stupid cheap, by SoCal standards.


This area is pretty close to Lake Elsinore’s downtown district, and strangely enough, the west side of the lake already has some fairly dense (10k/sq mi) development. The city’s clearly not getting much development or benefit out of the current situation, so… why not give it a shot? Why not rezone for something like beach city style development? Or why not buy a bunch of lots and pitch a few projects to the city? Doesn’t anyone want to build the next beach city?


Many moons ago, I wrote an introduction to North American railroad signaling, explaining the difference between fixed block signals (including wayside and cab signals) and communications based train control (CBTC), also known as moving block signals. Railroads that already have fixed block cab signals may not want to spend the money to entirely overhaul their signal systems to CBTC, and for institutional reasons may prefer to stay with traditional North American practices. In this case, there is a way to squeeze a little extra capacity out of the system.

To see how, let’s first remember what causes congestion and how cab signals work.

The relationship between speed and capacity is an upside down U. At high speeds, the number of vehicles that can get through is low, because of the need for more separation between vehicles. At low speeds, capacity is also low because no one’s moving. For any transportation line, there will be a speed (Vmax) that maximizes capacity. As long as speed stays above Vmax, the system is stable. If speed falls below Vmax, congestion quickly builds, because capacity drops and vehicles must slow down more to wait their turn. This is why a seemingly smooth-flowing freeway comes to a sudden halt when a few cars come up an onramp (and it’s why we have ramp meters).


Over to cab signals. The most common cab signal system on northeastern commuter railroads is a three-block, four-aspect system, with cab codes of 0, 75, 120, and 180 pulses per minute, corresponding to speeds of 0 mph (or really 15 mph but that’s another story), 30 mph, 45 mph, and maximum authorized speed (MAS). Historically, these systems were often designed with a mid-block code change from 30 mph to 0 mph, to avoid braking the train too soon and damaging capacity. Keep this in mind, as it’s important for squeezing extra capacity out of the line. (Transit systems usually have more, and different, speed indications, but the basic idea is the same.)


Ok, so in the context of a railroad running near capacity, we really don’t want to tell the train to start braking any sooner than needed to avoid crashing into the train in front. That might be enough to push us onto the wrong side of the speed-capacity curve, and cause delays to cascade backwards. That’s the beauty of CBTC; we don’t start braking until we need to. With fixed block systems, we have the wasted capacity of initiating braking in order to stop at a fixed block boundary, even if the train in front is nearly clear of that signal block.


However, there’s also wasted capacity inherent to the block layout itself. For example, in the graphic shown above, it’s very unlikely that the lengths of the two blocks between Train B and the red signal add up to exactly the stopping distance for Train B traveling at MAS. And even if it were, that might make it impossible to design the adjacent blocks to hit the exact stopping distance. On top of that, because of the effects of grade, it would virtually ensure that the block design would be very poor for train traffic in the opposite direction. Finally, if the block design is optimized for maximum speed, it may have a lot of wasted capacity at the other speed commands such as 45 mph. Signal block designers must consider all of these factors (grade, directional bias of traffic, expected operating speeds) when doing a block layout. Balancing these concerns will always result in some wasted capacity.

The way to get around this is and increase capacity a little bit is to code change every cab indication in every block using timers. In the example above, we can calculate how much extra stopping distance there is for Train B, calculate how much time it takes to traverse that distance at maximum speed, and then hold the cab indication at MAS for Train B for that amount of time when it enters the block. We still have the wasted capacity of fixed block boundaries, but at least we get rid of the wasted capacity from the block design.

Historically, this wasn’t done because railroads didn’t need that extra capacity, and the technology used for code changes (capacitor banks or cut sections) wasn’t great. However, with computer-based signal locations, it’s an easy programming change to implement all these code changes. You could even have multiple code changes in the same block. In fact, a considerable advantage of this approach is that if you have an existing fixed block system installed, you don’t have to install any new signal locations or cables – even if the existing block design is fairly inefficient, provided that the blocks aren’t ridiculously long. Note that for this to make sense, you’d have to get rid of the wayside signals (at least at intermediate locations) and use pure cab signals, to avoid confusing the operator with conflicting wayside and cab indications.

Here’s an example. Let’s say you have 32,000’ (just over 6 miles) of track between two interlockings. The signal designers of yore left you with eight 4,000’ blocks and the territory is good for 80 mph. Using ye old Pennsylvania RR braking chart, the braking distances to stop for 80 mph, 45 mph, and 30 mph are 6313’, 2230’, and 1108’. With this arrangement, you’ll have two blocks to stop, for 8000’ total. Conventionally, this would be set up with the first block receiving a 120 code (45 mph) and the second block receiving a 75 code (30 mph) timing out to no code (0 mph). With 4000’ blocks and only 1108’ to stop from 30 mph, we could give a 30 mph code for about 55 seconds. Don’t worry about the actual calculation, which is complicated by the fact that the train won’t have slowed down to 45 mph before entering the second block.

In this setup, for 80 mph speed we have 1687’ wasted (8000’-6313’), which is 14 seconds. Not huge but it’s something! For reference, the deadweight loss of a 4000’ block at 80 mph is 34 seconds. CBTC would be able to capture both improvements for a total of 48 seconds. By putting 14 seconds of 180 code (MAS) in the first block and then code changing to 120 code (45 mph) we can get about 30% of the improvement we could get with CBTC.

Back to the second block. Conventional wisdom often held that you should always see every signal indication (MAS, 45 mph, and 30 mph) on your way to stop. But really, there’s no need for the 75 code (30 mph) indication at all – the block is plenty long, so we could just code change from 45 mph to 0 mph. In our initial case, we could give 26 seconds of 45 mph code and then 0 mph.

We could also optimize for 45 mph, by ensuring that the train reaches 45 mph before entering the second block. This will allow us to hold up the 45 mph code as long as possible. In this layout, we only gain 1 second (27 seconds instead of 26 seconds) compared to the initial setup above – probably not worth it. To do this, we’d have to start the 45 mph code before the train enters the first block, so we’d have to code change the previous block to 45 mph – in this case 5 seconds before a train going 80 mph would be expected to leave the block, or after 29 seconds of maximum speed.


As can be seen, the capacity benefit of this approach will depend on the existing block layout and the target speed. In some cases it may present a reasonable benefit, considering that no new signal locations or cables are needed.

SoCal Rain: A New Hope?

Last year, El Niño brought lots of rain and snow to northern California, but SoCal residents watched storm after storm pass us by, leaving us with a fifth year of drought. The five-year period 2011-2016 was by far the driest on record, with 38.79” of rain compared to the previous record of 45.63” in the drought of the late 1980s, and an average of 73.70”. (Remember that in California we measure precipitation from October through the following September; this period is called the water year.)

There’s been some positive press lately about the rainstorms we’ve had so far this winter, with December 2016 the wettest month for downtown LA since December 2010. This is true, though this December (4.55”) wasn’t really in the same league as December 2010 (10.23”). December 2010 delivered more rain in one month than any of the drought years other than 2014-2015, which was juiced by tropical storm remnants in September 2015.

Looking at this year in context, we are off to a good start, with 5.95” so far. That already surpasses the worst year of the drought (2012-2013, 5.93”) and is less than an inch away from last year’s final total.


While last month was encouraging, every drought year has had at least one respectable month of rain. We need about 8.5” more this winter, which would give us an average year, just to save us from having the driest six-year period on record. To start making up lost precipitation from the drought, we need the storms to keep rolling through the next few months, so let’s hope they do!

Looking a little more broadly at SoCal, we can see that much of the region has fared better than LA.


(Note: ignore the below normal precipitation along the immediate coast and just offshore, which is a systematic error in the map.)

San Diego County, Orange County, and the Inland Empire are all a little bit more above normal than we are in LA. The SoCal mountain ranges have done even better; the five light blue areas east of LA are the San Gabriel, San Bernardino, San Jacinto, San Diego County, and Santa Ana Mountains (starting top left and going clockwise). This is really good news for the forests and wildlife in SoCal’s wild areas.

The unfortunate exception is parts of the Ventura County and Santa Barbara County mountains in the Los Padres National Forest. Since these areas depend on local water supplies more than other parts of SoCal, they really need to catch up. Let’s hope the storms keep coming and that everyone gets their share of the action!