L.A.'s Carmageddon: Would Building a Train Be Smarter Than Widening the 405?

Photo: sontag1

The “mother of all traffic jams,” in the words of L.A. County supervisor Zev Yaroslavsky, is coming to Los Angeles. On the weekend of July 16/17, an 11-mile segment of Interstate 405 will be closed as part of a $1 billion widening project. Reading of the expected traffic jams, and having recently returned from western Europe, where I traveled mostly by train, I was reminded of an earlier traffic nightmare.

This example I learned from Robert Caro’s 1974 masterpiece The Power Broker: Robert Moses and the Fall of New York. Robert Moses was New York City’s “master builder” in the mid-20th century, and famously hated public transportation. When he was in charge of building the Van Wyck Expressway to the new Idlewild airport (now JFK), F. Dodd McHugh, chief of the Office of Master Planning of the City Planning Commission, argued that a train line be part of the plans. Or at least, he suggested, when taking the land by eminent domain to build the expressway, why not take an extra 50 feet of width? The land would still be cheap, before the existence of the road increased population density and property prices, and the extra width could be reserved to build a train later. Moses vetoed these ideas.

Let’s see who was right by using my favorite street-fighting tool for mastering the numbers around us: comparing apples to apples. Here the apple is capacity; the comparison is the capacity of a highway to the capacity of a train line.

I’ll first estimate the carrying capacity of one lane of highway; it is the number of passengers who pass by during a fixed time (usually 1 hour). For this estimate, a lesson from driver-education classes is helpful. Driving courses teach, and many drivers-license exams test, the 2-second following rule:

Each car should leave a distance between it and the next car equal to 2 seconds of travel time.

If the drivers follow this rule, a single lane of highway carries one car every 2 seconds (no matter how fast the traffic is flowing!). Each car carries roughly 1 person, making for a flow of 1 person every 2 seconds. With 3600 seconds in 1 hour, a single lane of highway carries:

1 person    3600 seconds     1800 people

——— * ————  =  ———–

2 seconds     1 hour            hour

These figures are all rough anyway, so let’s call it 2000 people per hour. This estimate is one apple in the comparison.

The other apple is the carrying capacity of a train line. To make a fair comparison, I’ll compare highly developed roads to a highly developed train system: say a French, Swiss, or German train. (About the American train system, my mother taught me that if you cannot say something nice, don’t say anything.)

One train car may hold about 150 people. The whole train may contain 20 cars. And on a busy train route, one train might run every 5 minutes or 12 times per hour. Therefore the capacity of the train line is estimated with the following product:

150 people    20 cars    12 trains     36,000 people

———– * ——- *  ———  =  ————-

train car     train       hour           hour

These figures are also rough, so let’s call it 40,000 people per hour. (Even though the individual factors are highly variable, the final estimate is reasonable. According to the figures at this commuting blog, one track of the highly optimized Parisian commuter-rail system, the RER, can carry 55,000 passengers per hour. And Caro himself quotes “40,000 persons per hour” for a single lane of rapid transit.)

This capacity is 20 times the capacity of a highway lane! Even allowing that a train track could be wider than a highway lane, one train line could replace an entire highway, even a highway with five lanes in each direction (such as L.A.’s Interstate 405).

In theory, therefore, Robert Moses was wrong and city planner F. Dodd McHugh was right. And in practice, the city planner was also right. Not long after the Van Wyck Expressway opened in 1950, when air travel was much less widespread than today, the airport traffic alone exceeded 10,000 vehicles per hour– the official peak capacity of the whole highway. Anyone who lives in New York City will confirm that the situation has only gotten worse in the intervening decades. An original train line would have made the journey faster and more pleasant for so many New York residents and visitors. It would have also been easier (and cheaper) to build than the $1.9 billion AirTrain monorail completed in 2003.

The cost of building the original train line (3 miles of surface rapid transit) was estimated at $9 million in 1950 dollars. Let’s call the $9 million then a rough $200 million today. Multiply that by 2.7, since at 8.1 miles, the AirTrain is 2.7 times as long as the original line. And you still don’t come close to reaching AirTrain’s $1.9 billion price tag.

In a bitter twist, L.A.’s project of widening Interstate 405 includes building a carpool or HOV (high-occupancy-vehicle) lane. What the estimates above show, and the sad experience of driving to JFK airport confirms, is that the highest-occupancy vehicle is a train. If Los Angeles had learned the lesson, Angelenos today would not have to worry about Carmageddon.


As one who commutes on the 405 from the San Fernando Valley to the LAX area, I have often thought how my commute could be made better. My favorite idea -- and it would be a good tourist draw too -- would be a monorail from South Redondo Beach to Malibu with another feeder line from Valencia through the Valley to Santa Monica.

The problem with a rail line through the Sepulveda Pass (the section of the 405 which will be closed this weekend) is that it is too steep for a train. They would have to dig a tunnel of 7 or 8 miles, which would be very expensive. A practical alternative would be an elevated bus lane on TOP of the 405 (or perhaps alongside it on the canyon walls, like the Getty shuttle). We already have a dedicated bus lane in lieu of light rail in the Valley (the Orange Line). At first I thought the Orange Line was cheesy, but not only is it much cheaper to operate than light rail, it is also much quieter.



"...it is too steep for a train."

Too steep for a train? I suggest a visit to Switzerland, and a few trips on some of the mountain railways (Rochers de Naye or Les Diablerets, for instance). Then tell us anything in the LA basin is too steep for a train.

But to the original article, how many of those LA commuters do you suppose really need to physically move between the SF Valley and downtown to do their jobs? The highest occupancy vehicle is in fact a fiber optic cable :-)

Joshua Northey

It'll take another 40 years of baby boomers/gen-xers dying and/or retiring out of corporate decision making roles before we fully realize the huge transportation gains of telecommuting.

Hell at Merrill in 2006-2007 had a job which was 100% electronic, and they would still pay me 3 times as much to sit in their office and do it there rather then letting me do it at home for less (I offered).

At least at my current job which is 80% electronic I at least need to speak to my coworkers face to face once or twice a day.

Oh well institutions change direction like aircraft carriers.

Adam Hibbert

How do I like dem apples? Not a lot.

Primarily because one train car "may carry 150" - but does it, or do they tend to operate at something approaching the lower occupancy/capacity relationship you assume for automobiles? Taking your precedent and counting auto seats, not bods on seats, and multiplying your single highway lane by four or five, seems to make the scales balance. If it didn't the next question would be why those highways don't run coaches packing 50 seats every 2 seconds?


Your numbers only work if everyone in a single lane are going to somewhere within walking distance of the train stops. Far too many drivers get off at the ramp and then drive another several miles to get to their destination. European cities grew up along the rail or tram lines and everything is within 4 blocks of the line. Where in your calculation do you figure in the impossibility of reasonably getting to the train from home and to the office from the train?


The title from the Twitter feed has, "In terms of increasing capacity, yes" added to the end of the article's title. He is arguing about capacity, not ease of use. I don't have a lot of city experience, but the times I've used Calgary's transportation system (I know it is little league compared to LA) I've thought it worked well, besides needing more parking at transit stations. If rail was used to get to the center of the city or other high density areas, that would ease traffic congestion immensely. If the walk is too much once you get off the train, catch a bus from the station.

I believe that there are enough people within walking distance of potential train stops to offset another lane of traffic. And people will adapt to train travel. It will be a pain at first, but it will become part of their routine and won't think twice about it once settled in.


I think there have been countless examples of freeway closures not resulting in the apocalyptic traffic jams that anti-transit people tend to predict. The theory of induced demand states that increased capacity actually generates new driving (people driving instead of taking transit; driving closer to the peak period; taking the highway route rather than surface routes - referred to as 'triple-convergance' and nearly guaranteeing that new capacity makes congestion working); and that subversively, removing highways reduces overall demand on the system.


The Highway Capacity Manual sets the maximum capacity of a freeway lane at 2,200 vehicles per hour per lane. You need to cut back this number for narrow lanes, roads with lots of turns, and roads with hills. So your math isn't too far from the engineering practice. Also, auto occupancy is often assumed to be 1.1 when no other information is available.

I agree that trains make considerably more sense for capacity studies like this. Running the math on capacity alone will always show trains as having the advantage. But we also need to consider the fact that people neither live nor work on the expressway; you need to calculate the capacity and operations of the collector/distributor network as well. While transit-oriented developments help people live and work closer to the rail line, convincing developers and tenants is a very difficult proposition.

Taking a city built around trains and making it fit the automobile is very difficult and expensive (London/Paris), and doing the opposite will be the same. Transportation is a derived demand, and our transportation networks are the product of generations of policy decisions. Simply replacing a freeway with a rail system will not solve anything.



It seems only fair that we also consider the capacity of a sidewalk.

The average highway lane is 12 feet wide; an average person walks three miles per hour. This gives us 190,080 square feet per hour. If we give each person a generous four square feet to occupy, we get a capacity of 47,520 people per hour.

Obviously, then, we should close all the highways to vehicular traffic and make everyone walk everywhere.


You estimate is fine, as is your conclusion, but you e estimate THE WRONG QUANTITY.

The key number to understand human interaction with a transit system is not carrying capacity, but MODE TRANSFERS.

That is, how many times does a passenger have to change between modes of transport to get where they want to be. Bitter experience shows that Americans will only tolerate zero or sometimes one mode transfers. For a typical American, using the high capacity train involves two mode transfers:

place of Origin -> station / transfer / station-to-station/ mode transfer / station to destination.

By contrast, driving to long term parking only involves one mode transfer ( car to parking shuttle) Even better is having your spouse drop you off at the airport : zero mode transfers.

So those trains may have high potential capacity, but there rider ship will be limited to those who live AND WORK close to a train station.

Returning to Moses, this calculation shoes Moses did get JFK transit wrong, provided that the train goes INTO the terminal, like at O'Hare or Dulles. Going near the airport, like Oakland, still involves a mode transfer, and there is not a wise use of transit dollars.


Eric M. Jones

"PaulD: The problem with a rail line through the Sepulveda Pass (the section of the 405 which will be closed this weekend) is that it is too steep for a train."...is exactly correct. Those who doubt this have never been there. The Western mountains have their own unique challenges.

My own solution to LA traffic is to switch industrial and residential spaces. Move all the industry inland and put all the people near the coast. Now there is far too much of the reverse, caused basically by the fact that LA grew up from the coast. This wouldn't be fast or easy, and would have to be driven by punitive taxation, but over the long run, it is the only thing that would work.

Start by moving LAX to Palmdale with fast feeder rail to various points.


Let's think ahead to 2050. The US Census Bureau projects a population of 392 million a 50% increase from 1990. How many times can we widen the highway? We have to think differently about how we live and move.

Joshua Northey

Why not just make actual single occupancy vehicles? Cars the size/weight of motorcycles?

You could still have larger cars for those rare occasions when someone needs more, but even a smartcar is frankly war more then most people need. Combine smaller vehicles with automated control while on the freeway and you could have a much more efficient transportation network while using the same infrastructure and preserving people's desire to avoid modal changes and develop in a sprawling unplanned way.

James Halliday

I always liked the idea containerizing people.
You buy a little powerless-pod, or maybe has a small electric motor for short trips on minor roads. When you get to a major artery your pod just hooks onto a drag-line (or loaded onto a train-like vehicle) that recharges it and distributes you automatically to the vague locality of your destination.
Or the ultimate (until we get around to teleportation) fantasy of falling asleep in your pod as you're halled to the airport, loaded on the plan, unloaded and parked outside your hotel.
Obviously all sounds a little bit ridiculous, but seems to blend together the efficiency of centralized transport (any of you hire a gulfstream, rather than getting on a scheduled flight) with the ownership of your own personal space (i.e. the car).
If you're still hell-bent on public transport, then you could just hire the pod each-way.
OK, you're probably still not convinced - just it eternally pisses me off that 'logistics' seem to have completely and utterly bypassed 'people'


James Halliday

Sorry - "hauled"


Regardless of how close or far away a destination might be to a train station, you still need to ask yourself what is the maximum width possible/tolerable in a highway. I live in Atlanta where we have I-75/85 running straight through the city.


Despite being gigantic, heavy congestion is constant on it at all hours of the day. At this point widening it would literally mean knocking down some of the very buildings that people are trying to get to in the first place. Thankfully we do have an alternative in the form of MARTA which is a much faster and cheaper way of reaching the cities three major business districts and airport.

Steve S.

"The crisis of today is the joke of tomorrow" - HG Wells

Not to downplay the impending carmageddon, and the population estimates for 2050 - but how often do these oft dire predictions come to fruition? Have we gotten better at predicting the future than in the past? According to a recent freakonomics podcast, we have not.


LA is not organized nor dense enough to support public transportation the way people wish it would. This is a cute little utopian wish; but having a car is a part of living in LA. I like the pod idea, public trans would be awesome but it needs to be more adaptable to individuals or smaller groups to fit the needs of Angelenos.