Solving Traffic Congestion

If a stretch of highway is often congested, we should add another lane to increase capacity. Wrong.

In “The Fundamental Law of Road Congestion: Evidence from U.S. Cities,” researchers show any increased capacity from additional roads is temporary.  Traffic increases to fill the added capacity.  The study’s startling findings include:

  • The number of vehicle-kilometers traveled increases in proportion to the available lane-kilometers of roadways.  If there are more roads, additional drivers start using those roads until congestion returns to the previous level.
  • Increasing the lane-kilometers for one type of road does not significantly reduce congestion on others.  In other words, widening highways doesn’t reduce congestion on city streets.

And perhaps most confounding:

  • Because roadways have natural levels of congestion to which they always return, mass transit projects do not reduce traffic.

So, how should we handle traffic congestion?

The authors conclude that the most effective approach is to charge a fee for cars to travel on roads during peak congestion hours.  This so-called congestion pricing is not yet common but has been applied successfully – and controversially – in major cities around the world. The negative reinforcement encourages people to drive less or to find alternative methods to get to their destinations.

Anyone from London want to chime in?

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3 Responses to Solving Traffic Congestion

  1. Lyndsey Spurgin April 30, 2012 at 5:02 am #

    Hello from London!

    Congestion in London is a constant debate, the age old comment is that traffic in London’s average speed is 11 mph – which is the same as when the motor car was first introduced!

    We do have the congestion charge in London, meaning that Monday-Friday business hours all cars have to pay £10
    it is very much agreed that this has discouraged people driving in – but average speed hasn’t increased…..according to the Mayor this is good as London is safer for cyclists.

    The real test is going to be this summer with the Olympics – will London grind to a halt?!
    If you are coming to London give yourself lots of time to get to the venue and use the tube!

  2. Scott Lawley April 30, 2012 at 6:01 am #

    Did you ever notice how all of the bike racks at the SAP office in Walldorf are always overflowing, even on rainy and cold days? Why is that? I try to bike everyday to the Palo Alto office, and I can’t help but notice the empty bike racks. I am not a big believer in negative reinforcement, and I think with this particular problem, when seeking alternative modes of transportation, ultimately, a significant lifestyle change is required. Perhaps more focus should be given to enhancing the experiences of alternative modes of transportation in order to ease their adoption. Ask people that don’t bike why they don’t bike, and their answers are “it’s too dangerous” or “I live too far away” or “my bike is too old”. How can a sane person say to themselves that they would rather sit in heavy traffic than ride a bike, and yet they let such small issues get in the way. And just think, if they got that bike out, cleaned it up, and rode to work, they might even be able to drop a few pounds while doing it.

  3. Colin Cooper May 2, 2012 at 5:08 am #

    Hi Jonathan,

    The London congestion charge certainly worked in that if it hadn’t been there we would probably have been massive gridlock that we have avoided so far.

    In fact in the first year it worked too well. If I remember correctly they forecast something like a 20% reduction in traffic as a result of the charge. In fact they got a 25% reduction which meant that the equivalent of that 5% of revenue from the charges was not being collected leaving a hole in the funding. Key to this was adding approximately 200 more buses onto the streets as well so people could move around easier.

    Taking the hassle out of public transport has to be the key to diverting commuters from their cars so integrating Tubes, buses and trains together on the Oyster card and capping the amount that it can cost in a day means there is no need to drive into the city during the week unless you have a stack of things to deliver.

    There’s always room for improvement but the system works.

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