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.

Leave A Comment

Comments are moderated and generally will be posted if they are on-topic and not abusive.



View All Comments »
  1. Joshua Northey says:

    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.

    Thumb up 4 Thumb down 1
    • James Halliday says:

      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’

      Well-loved. Like or Dislike: Thumb up 6 Thumb down 1
  2. Dan says:

    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.

    Thumb up 2 Thumb down 0
    • Jim says:

      Ironically, the Google Maps link you posted shows a very light traffic load. Not discounting your comments, just amused at the irony of the static photo from the link.

      Thumb up 0 Thumb down 0
  3. Steve S. says:

    “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.

    Thumb up 4 Thumb down 0
  4. Lyndon says:

    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.

    Well-loved. Like or Dislike: Thumb up 9 Thumb down 1
  5. Dave says:

    Your estimates may or may not be valid. First of all, anyone who has ever lived in L.A. can tell you how few people follow the two-second “rule.” So the capacity of the highway lane is probably closer to 2500.

    But the much bigger error is the train. It may well have a capacity of 40,000 people per hour, but you’re making the same mistake the central planners often make in so many places: assuming it will ever be filled anywhere near capacity. In a place like L.A., I can guarantee you it will not be.

    Thumb up 5 Thumb down 1
    • James says:

      When I’ve lived in places where there are trains, they do seem to be filled to capacity – and sometimes beyond – at peak times.

      Thumb up 2 Thumb down 0
      • Philo Pharynx says:

        That may be true, but that doesn’t mean that putting a train anywhere will generate that kind of result. Many of the cities with excellent public transportation had most of their growth before the 20th century. They have a population density and distribution that makes public transit efficient. In many of these cities it is more difficult to deal with a car than public transit. The Southern California sprawl is built very differently – it’s built around the automobile. Changing this would require major rebuilding and cultural changes.

        Thumb up 1 Thumb down 0
  6. Simon says:

    If you built a train, you could get people up and down the 405, but for many people in LA, the 405 is only a part of their commute, not the whole thing. There isn’t much high-speed public transit infrastructure in the vicinity of the 405. (There is a big empty space on the LA metro map around West LA, where the 405 is.) Virtually no one wants to ride a bus in LA when instead of driving, because buses have to travel on city streets, which are even slower than LA’s clogged highways; make frequent stops; and operate on an unpredictable schedule.

    For a train along the 405 to interconnect with existing public transit infrastructure, the Purple Line would need to be extended to run to the 405, and/or a new line along Santa Monica or Sunset would need to be built. This will happen eventually, but the cost is estimated at $4-$9 billion (depending on which lines are built) and will be completed in 2036. When this happens, I’m sure the LACMTA will consider a train along the 405, but it’s a long way off.

    Thumb up 3 Thumb down 0
  7. Ivan says:

    Your solution, though scientifically correct, is also obvious in showing that you really have not spent any time in LA or don’t really understand how a rail system with the 405 would work. This isn’t like New York where the train is within about 15 minute walk to anything, LA is much more spread out and would not only require numerous stops, it would require other trains to pick those people up at those stops because LA is just too damn big. I’ve lived in both LA and New York and I can tell you, they are completely different monsters so next time you try to show “LA” how you’ve found a perfect way to fix your problem, try spending one month here just driving around on different stops at the 405 and you’ll realize how silly you theory is.

    Thumb up 4 Thumb down 1
  8. David says:

    wow pretty detailed information. All i know is im going to be FAR AWAY from here. Plus, I just got this awesome car-mageddon tshirt at http://isurvivedcar-mageddon.com/

    Thumb up 0 Thumb down 0