Sunday, July 23, 2006

Los Angeles Traffic

Finally, a clear-eyed explanation. Really. Includes a modest proposal to import new highway capacity from Mexico.

When not driving in southern California traffic, which I do nearly more than I can bear, I try hard not to think about it -- let alone blog about it. But USC's Peter Gordon, rumored to live in a pedestrian-0riented neighborhood, went ahead and blogged that while I was in Mexico most of July, weakly holding strong opinions on Jaliscan tequilas and Oaxacan moles, the LA Times ran two pieces revisiting the arguments that (a) sprawl is not to blame for our worsening traffic and, relatedly, that (b) inadequate road capacity is. The first is an op-ed by UIC's Robert Bruegmann, boisterous author of the recent book A Compact History of Sprawl; the second an article.

The research on these issues is extensive but unfortunately not exhaustive, meaning there is still some credible evidence to support virtually all sides of these issues.

But wait, you ask, what do I think? A few years ago Rutger's Dan Chatman and I looked at how job sprawl affects commutes, finding some evidence that it can act to shorten them on average nationwide. (I'll post a summary separately but note this is consistent with theoretical work by MIT's Bill Wheaton that since firm suburbanization is likely at the cost of some agglomeration economies it stands to reason it may be at the benefit of improved market access, including access to labor markets, meaning access to suburban workers.) Shorter commutes should translate to lower required wages, all things considered. So while commutes are lengthening, they aren't as much as they would in the absence of job suburbanization ... maybe. (Our data are not the greatest, even if they are the best we know of.)

The capacity argument is probably best known in the work of Anthony Downs, including the associated Downs' Law stating that traffic congestion is at least somewhat self-correcting, so more capacity will rarely relieve congestion over the long run, though it certainly will provide additional travel benefits. This is now mostly referred to as the induced travel debate, on which UC Berkeley's Robert Cervero has recently produced many useful results.

On the policy front, our gleaming governor Arnold Schwarzenegger recently advocated a larger than expected capital investment plan for the state, with $21 billion earmarked for roads over the next 5 years. The state itself estimates a road shortfall of $140 billion. Thus, Martin Wachs, now back in the southland heading Rand's transportation (and Space!) program, probably spoke to the LA Times for an hour but the only quote that survives is, "I'm convinced that there isn't enough money."

(I couldn't help but notice, while researching A-list tacorias in La Condesa, that Mexico City found enough money to start double-decking its main ring highway, the Periferico, with a good part now in service. While ever more US car production is headed Mexico way -- attracted by lower wages -- and the Periferico deck is of a precast, modular form, I suppose it would be naive to suggest we simply import Mexican-made second decks for segments of the 405 and 101 freeways to leverage that $21 billion a bit.)

And yet, we planners are well aware that there are also articulately enthusiastic arguments that too much money is going into additional road capacity. The pros and cons of cars are perhaps uncountable but UCLA colleague Paul Ong and I wrote the following short essay about LA traffic anyway. It originally appeared in the UCLA Institute of the Environment's annual magazine of graded assessments of different elements of the southern California environment.


By R. Crane and P. Ong, UCLA Institute of the Environment, Southern California Environmental Report Card 2004.

Almost everyone complains about the traffic in Los Angeles, and for good reason. We hold the dubious honor of being the most congested and polluted region in the country. Pollution follows partly from congestion since cars, trucks, and buses are the primary sources of many air pollutants and gridlock exacerbates pollution by causing higher exhaust emissions than free-flowing roadways. In addition, our dependence on cars is said to isolate transit-oriented neighborhoods, rob us of exercise and time, and weaken social ties.

How did we get into this mess and what, if anything, can be done? The short answer is that the region’s economic success results in lots of people with lots to do. And, like people pretty much everywhere, they mostly do it by car. Southern California has the 10th largest economy in the world, containing 54% of California’s jobs. On the other hand, the state has less road capacity than all but 2 of the 65 largest U.S. regions. Absent more roads, this strained capacity can be relieved only by substantially less driving per person, many fewer drivers, or both.

Either solution would be a neat trick. Traffic is the product of complex interactions involving the level of economic activity, the region’s spatial structure, the design of the transportation network, and the choices facing individual travelers. As a result, there is no silver bullet for any one of the associated problems, however much we might wish otherwise.

We cannot do away with traffic and traffic problems altogether, but we can manage them better. So, while it is easy to complain, point fingers, and make promises, it is more useful to clarify our circumstances and opportunities, modest though they may be. To show this, we first look at how this region is performing comparatively, then discuss the policy options and, finally, grade the region’s progress in managing traffic problems.

Table 1 presents recent urban form and transportation data on four U.S. regions. New York and Chicago are comparable to Los Angeles in population size, while Houston has at times been ranked as the region with the worst air pollution, briefly replacing Los Angeles for this dubious distinction.

To begin, note that the reputation of Los Angeles as having extreme low density sprawl is an urban myth. Los Angeles has a form typical of metropolitan areas that matured during the latter half of the twentieth century. Population density measured in persons per square mile here is low for the metropolitan area as a whole, particularly compared to the New York metropolitan area. Chicago, however, has a lower population density despite being an older region. And the density in Houston is only one-third of that for Los Angeles. When non-urban areas are excluded from the calculations for the larger urbanized complex, Los Angeles is actually more densely settled than the other three, including New York.

Another urban legend is that Los Angeles is disproportionately automobile dominated. Although the number of personal vehicles per household in Los Angeles is twice as large as in New York, Houston has more cars per person and Chicago is close behind. Moreover, one in eight L.A. households does not own a vehicle. Indisputably, New Yorkers are in a league of their own when it comes to shunning a car, and this is consistent with their extraordinary reliance on public transit. New York has a transit system that is a quantum leap more extensive than in any other metropolitan area in the U.S. Removing New York from the comparison changes the relative performance of Los Angeles. A respectable number of Angeleno workers share a ride in either a car pool or on public transit, for a combined rate that is similar to that for Houston and Chicago. The number of vehicle miles per person also indicates that Los Angeles is not at the extreme.

Finally, the Texas Transportation Institute consistently ranks Los Angeles as having the worst traffic congestion in the nation, but average commute time for its residents is considerably shorter than for New Yorkers, and roughly comparable to Chicago and Houston.

Despite the mixed results in the comparison of urban form and travel patterns, there is no disputing the air pollution problem in Los Angeles, which the EPA rates as the worst in the nation. Table 2 provides comparative statistics. In 2000, Los Angeles had 88 days of unhealthy levels of air pollution. While this is a dramatic improvement over 1993 (137 unhealthy days), Angelenos suffered noticeably more unhealthy days than their counterparts in the other three regions.

Mobile sources are a major contributor to air pollution, as the statistics for carbon monoxide (CO) emissions indicate, and cars contribute more to air pollution in Los Angeles than in the other three regions. The amount of CO produced by passenger cars per household in New York is the lowest because a smaller percent of New Yorkers own a car; but interestingly, the emissions per vehicle are the highest for New York, perhaps due to the way New Yorkers drive and/or higher emissions per vehicle. For the other three regions, this indicator is roughly comparable, with Houston faring the worst by a small margin.

Our comparison of urban form and travel patterns indicates that the severity of traffic and pollution problems in Los Angeles is not determined solely by population density or high car use. Other factors such as the physical geography contribute to the problems.

Transportation planning used to be pretty easy, even in LA. The task was mainly to design streets and highways connecting concentrations of people (emerging towns) to where they wanted to go (jobs and commerce). In much earlier times, fixed rail and bus transit played dominant roles in these designs. However, the primary, almost exclusive, focus during the post-World War II era was to build street and highway systems to accommodate the most flexible and convenient mode, the car.

In doing so, planners reinforced patterns of urban and regional development that moved millions of residents and jobs away from the urban core to emerging centers throughout the region. It would be wrong to argue that freeways created the suburbs, but they worked hand in hand with a decentralized economic base, the rapid increase in women in the workforce (which complicates family commuting patterns and increases income availability for larger houses), the tax subsidy for home ownership, and the desire for a single-family home with a backyard.

Moreover, there seemed to be no downside to automobile dependence. Initially, the car was a huge environmental improvement over its predecessor, the horse, until air quality problems were conclusively linked to automobile travel in the 1950s. The displacement of residential neighborhoods and the impact on habitat were at best secondary concerns— at least in the public eye—until the 1960s.

We all know the urban population in Southern California rose rapidly through the last century, but urban travel grew even faster. In the last two decades, total region-wide “vehicle miles traveled” (VMT) nearly doubled while the population rose 44 percent. Capacity grew even less, with arterial and local lane-miles increasing by only 20 percent. Why? Key trends behind travel demand include the steady increase in women in the work force, leading to more drivers per household; the growth in real incomes that raised car ownership levels and lowered the importance of transportation costs in choosing where to live; and the rising proportion of nonwork-related trips (now over 60% of all trips). On the supply side, California highway building became increasingly subject to a fiscal squeeze after the 1960s. Construction costs climbed, driven by escalating urban land prices, while real revenues fell as gasoline tax revenues failed to keep pace with VMT or even inflation.

As the gap between travel demand and roadway construction grew, so did regional congestion. Congestion cost Americans an estimated $70 billion in 2001, from lost time and extra fuel consumption. Public opinion polls show traffic congestion is often cited as one of the most pressing urban policy problems.

In addition to all these demand and supply factors, which often reflect larger demographic and economic trends, we as a society fail to hold individuals responsible for the traffic costs they impose on others. Both air pollution and congestion are classic cases of market failures that create social cost for others, often known formally as externalities.

The costs of automobile emissions include the impact on the health of those along the roadways, in the region, and ultimately throughout the world. The cost of congestion is more localized to the extra time that others must spend on the road. Each additional car slows traffic, and while the impact on any one other car is tiny, it adds up when summed across thousands or millions of delayed travelers. All of us ignore how much we slow other cars down, which is at the heart of the problem.

To summarize, pollution is explained by the amount and congestion of traffic. Volume growth is explained by demographic and lifestyle changes and economic development. Congestion, in turn, is both a capacity and an incentive problem. In particular, while we should expect some congestion as evidence of a successful economy, there will always be too muchwhen individual drivers ignore the costs they impose on society.

Solving our traffic problems is difficult because they are nuanced, moving targets. One should be leery of simplistic solutions. When stuck in traffic, for example, the knee-jerk reaction is to argue for more road capacity. While understandable in light of the regions’ low road and highway investments in recent decades, finding funds for new construction is extremely problematic. Moreover, more capacity will not by itself substantially reduce congestion. Urbanist Anthony Downs once famously stated that travel demand on freeways rises to meet capacity. If new lanes are added, congestion problems might be lessened in the short run. But that reduced congestion will attract drivers who previously used other routes, traveled at different times of the day, used other modes, or drove less or not at all. New roads and lanes do provide additional mobility and other transportation benefits, but increased road capacity provides less congestion relief than one might expect.

Policymakers must perform a balancing act, addressing air and other environmental concerns without excessively sacrificing the ability to get where we need and want to go. Ideally, achieving one of the objectives should not come at the expense of the other. Feasible approaches include increasing carpooling (including vanpooling), shifting trips to mass transit, adopting efficient pricing, and altering land-use.

“Travel demand management” is one attempt to increase the number of passengers per car. One notable experiment in this vein is the trip reduction policy of the South Coast Air Quality Management District (SCAQMD), adopted in the late 1980s. The initial attempt to increase ridesharing was controversial because many firms argued the regulatory burden was unjustifiably burdensome and expensive. Moreover, only small driving reductions were credited to the early years of the program, which is now voluntary. An alternative strategy is rewarding carpooling by establishing high-occupancy-vehicle (HOV) lanes, which allow eligible vehicles to travel at higher speeds. The hope is that people will respond to the time savings by forming more carpools. Unfortunately, the evidence suggests that dedicated lanes for car-poolers stimulate only a small increase in ride sharing. The average number of occupants per vehicle (about 1.2) is little more than it was twenty-five years ago, before the widespread introduction of HOV lanes.

A second major strategy is to shift trips to mass transit. Intuition suggests that better routes and more comfortable trains and buses will encourage more transit use, thus getting drivers out of their cars. The question here is not the absolute benefits of transit investments, but identifying the most effective use of public funds. In a select few Los Angeles corridors, where the density of both population and destinations assures high ridership, providing heavily subsidized rail transit trips is reasonable in comparison to other congestion-relief and mobility programs. It is wishful thinking, however, to believe this is true for much of the region because most parts of L.A. do not have the density to support rail transit. More sensibly, Los Angeles should enhance its bus service, including express buses, modernizing and expanding the bus fleet, improving the management of the numerous transit systems, and coordinating services across agencies.

For most economists, the Holy Grail for traffic-related problems is charging drivers the costs (externalities) they impose on others. When forced to pay the real price of travel, some individuals would reduce their driving, share the cost through carpooling, and find other means of making trips. Unfortunately, imposing such a charge has not been politically feasible because drivers vehemently oppose paying for previously un-priced travel. With minimal popular support, the pricing solution has been tried in a very limited fashion to address congestion but not environmental externalities. Despite the limited application, the results are revealing.

One example of congestion pricing is the establishment of toll lanes down the median of State Route 91 in Orange County. The franchise for this venture was granted to a private contractor, and the current tolls vary by time of day according to demand. This application of congestion pricing never met with serious opposition because the toll lanes provided new capacity immediately adjacent to existing free lanes. Travel time in the free lanes dropped by as much as twenty minutes as some traffic diverted to the new capacity. This project demonstrates two important points: (1) In a highly congested corridor, people will pay to reduce their travel time, and (2) Even those who do not wish to pay are made better off by the toll facility when traffic is diverted from existing free lanes.

There are two other promising ideas. The first is creating high occupancy toll (HOT) lanes. Because the high occupancy vehicle lanes on the Interstate 15 north of San Diego had been underused, local officials allowed single occupancy vehicles to “buy into” the carpool lanes, initially with the purchase of a monthly pass. The revenues from this project are used, in part, to finance express bus service along the corridor, thus alleviating some of the concern that pricing projects inherently favor upper income individuals who can afford to pay for faster travel. The other promising idea comes from abroad. Singapore and London have implemented congestion pricing—charging more for driving at peak hours—for their central business districts, and this has produced popular results in relieving downtown and regional congestion, and generating revenue for public transit.

Finally, many planners promote various urban design strategies to reduce car use, alternatively known as the New Urbanism, Transit-Oriented Planning, or Smart Growth. These vary in their details, but the idea is that denser and more-mixed use urban development, especially if focused around transit systems and stations, will both reduce VMT and increase walking and transit use. However, these proposals face two uncertainties: the best recent research does not consistently support either claim, and the higher densities could generate yet more congestion. Nonetheless, some project details hold promise, and may well deliver benefits in certain cases.

Each of the above strategies provides only partial solutions. The lesson is that policy responses should be multifaceted because there is no monolithic monster to blame for our traffic ills. More effective use of road pricing can better align individual behaviors with the social costs of traffic, as can more strategic investment in road capacity and express bus systems. The benefits from these actions can be enhanced through better land-use planning and urban design.

Policymakers must perform a balancing act, addressing air and other environmental concerns without excessively sacrificing the ability to get where we need and want to go.

Investment in road capacity: The road network has not kept pace with growth, leaving the region with close to the least capacity per driver in the nation. Grade: D

Investment in and management of transit: Unproven and expensive rail investments have been at the expense of proven bus service. The good news is that Los Angeles now has more express bus routes with dedicated lanes, and is purchasing more buses, albeit under court order. Grade: C

Pricing: California is experimenting with congestion pricing on freeways, but its application is extremely limited and mostly outside of LA. Grade: D+

Land use planning: Los Angeles works reasonably well as a car-based system of relatively dense subcenters. Sprawl complaints lack hard evidence, and the region compares well by national standards. The challenge is balancing high-density in-fill, such as Playa Vista, with mixed uses while conserving open space and managing congestion. Grade: B

ACKNOWLEDGEMENTS The authors are listed in alphabetical order. We thank Brian Taylor for his comments and Matthew Graham for assistance in assembling the emissions data.

DATA SOURCES American Public Transportation Association, Public Transportation Fact Book Texas Transportation Institute, 2003 Urban Mobility Study U.S. Bureau of the Census, 2000 Census Data. U.S. Bureau of Transportation Studies, Highway Performance Monitoring System (HPMS) U.S. EPA, Air Quality System and National Emission Inventory


jesse said...

this is fascinating, thank you. Because of its status as car-Mecca, it's always interesting to see how LA really fares compared to other cities in terms of pollution, congestion, etc. The results sometimes do come as a surprise.

Peter McFerrin said...

Prof. Crane, I have a question concerning the definition of "metro area." Does the figure for that include undevelopable national forest and mountain lands? Does it include waterways within a metro area? Because the development density listed in the chart for New York is so much higher than that for Los Angeles, I am willing to guess that the methodology used for determining "metro area" includes unbuildable land but excludes water. This seems rather silly, given that the Angeles, Cleveland, and San Bernardino National Forests--and the mountain ranges on which they sit--are effectively as impassable a barrier to travel as any body of water.

In any case, the distinction between "urbanized area" and "metro area" is relevant here because, as most serious students of urban planning know and as you mentioned, the urbanized portions of Greater Los Angeles have the highest development and population density of any urban area in the country. Prof. Cervero and others have said that the City of Los Angeles itself has "problematic density," in that population is distributed in such a way that there are only a few corridors in which reserved-ROW transit could be effective (Wilshire, Downtown-Koreatown-Hollywood, maybe the 405/Sepulveda corridor between Sherman Oaks/Van Nuys and LAX) but there are many places in which density and congestion are too high for buses in mixed traffic to provide effective mobility.

Brian V said...

A year later but I feel the need to comment.

1) Buses: A bus trip of significant distance in LA takes 2 to 3 times longer than id done by car. The weakness is LA is so large that it takes hundreds of routes to cover it. The result is any trip usually takes two or more buses to accomplish. The time for transfers and connections adds up quickly making a car ride seem far more attractive. More buses on the road may help short distance commuters, but wont save freeways where people are traveling longer distances.

Subways: Well planned subways such as the Metro Red line have the promise of huge success. At 7am the red line is standing room only by its 2nd station stop. Where the bus moves slow on congested streets the red line flies underground. There are at least 3 or 4 other corridors in LA that could easily support a subway. With trains every 10 minutes, convenient park and rides, and on time station stops the subway is a luxurious way to travel.

Capacity: Adding more capacity is not always the answer. But in LA there are bottlenecks where capacity is the issue. With the exception of a half dozen 2 lane canyon roadways, the anemic 101 and 405 struggle to connect the valley and LA proper. The connecting stretch of the 405 is the number one traffic delay zone nationally over decade running.

Carpools: A great idea for people people who live close to one another, like one another's company,work near one another, and arrive and leave at the same time. Unfortunately finding a carpool partner is often more difficult than finding a spouse.

I think the future of LA will depend on more of everything. Subways, buses, more lanes, and better urban planning. I also think it will depend on LA governments, businesses, and residences changing their habits. Is there a compelling reason telecommuting is the exception and not the norm for some office jobs? Is there a reason 8am is still the standard start time for most businesses and schools, why not 7 or 9? Do large central offices really save money compared to smaller regional offices when we consider traffic and pollution? Our traffic problems are mostly due to too many sheep trying to follow the norm at the same time. Any fix will require everyone to step outside the norms.

Muralidhar Rao said...

The problems are universal. Perhaps it is far more acute in Bangalore because of the sudden acceleration in growth over the past few years. I have listed my suggestions in my blog which can be accessed at
These can apply equally well to other cities, including LA.
Muralidhar Rao

Anonymous said...

Los Angeles Rush Hour
Traffic Solution

Los Angeles should look back to the LA Olympics when LA restricted commercial traffic during
Rush Hours. Traffic really moved well.
A similar policy today would move traffic more smoothly & cut down of freeway accidents involving big rigs. Why would the owners of trucking companies want their drivers unneccessarily bogged down in LA rush hour traffic burning
drivers' wages & fuel? Would rerouting & rescheduling truck traffic be better for all concerned.


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