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Want less traffic? Build fewer roads.

Want less traffic Build fewer roads plus maths org


If closing roads might help traffic flow, the negative effects of expanding a road network can be observed as well. For instance, in the late 1960s the city of Stuttgart decided to open a new street to alleviate the downtown traffic. Instead, the traffic congestion worsened and the authorities ended up closing the street, which improved the traffic.

Stories like these abound and as you might suspect, some mathematics is lurking behind them all. Indeed, in 1968, the mathematician Dietrich Braess, working at the Institute for Numerical and Applied Mathematics in Münster, Germany, proved that "an extension of a road network by an additional road can cause a redistribution of the flow in such a way that the travel time increases." In his work Braess assumed that the drivers will act selfishly, each of them choosing a route based on their own perceived benefit, with no regard for the benefit of other drivers. It's an assumption that reflects the harsh conditions of rush hour traffic rather well!

The phenomenon Braess observed, now called the Braess paradox, is not really a paradox, but just unexpected behaviour showing that we are not very well equipped to predict the outcomes of collective interactions.

The closing of 42nd street and the Cheonggyencheon stream restoration project are just reverse examples of the Braess paradox, where the removal of one or more roads improves the travel time along a road network.

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The logic seems sound until I look at El Camino Real in Silicon Valley.

It is super congested, and closing the roads that lead into it won't make it any less congested. 

Pity the poor traffic engineer. There is probably no greater gap between ANECDOTAL "common sense" thinking and actual science than on this topic.

Basically the thing you need to understand is that TRAFFIC ENGINEERS DO NOT ARGUE ABOUT THIS ANY MORE. The research, however counterintuitive, has been so thoroughly replicated that there is no point in replicating further from a scientific point of view. The real question is WHY DON'T YOU BELIEVE IT?!?!? And the answer is almost certainly, you are relatively wealthy and a car owner.

So let's take the example of El Camino Real, which I have been following. They aren't talking about closing the roads that lead to it Panda -- they are talking about closing ONE LANE in each direction for a dedicated bus lane. The calculations say that doing so would make the bus like twice as fast and only increase car traffic a few minutes. But you don't ride the bus, do you? You probably don't know anyone who does, or who would even consider doing so if the bus was a lot faster. You probably don't even know the NUMBER of the bus route (22/522). Therefore (not to call you out personally because we all know you are a kind and just panda) you rightly conclude that this move has no upside for you and a lot of downside. But even there you're wrong because every person that chooses to take the bus instead of driving is one person who is no longer clogging up El Camino.

In the bigger picture the Bay Area is a perfect microcosm of why your type of thinking is SO wrong. There is actually EXTREMELY robust demand for public transit, far more than can be handled by the public agencies -- which is why every single Caltrain is packed, even at 8AM on Sunday mornings, and more importantly why Google and Facebook have to run gigantic private bus fleets. Unfortunately this strong demand is countered (and then some!) by strong NIMBYism from both left and right... and most town governments are too weak to re-balance the incentives for everyone. Sunnyvale actually does the smart thing, which is to allow far fewer parking spaces than jobs, and leave it up to the companies to incentivize their workers not to drive -- which I think a lot of them do by either providing private bus service and/or paying for all public transit by their employees. Obviously another type of solution which the Libertarian wing loves is to give out Uber vouchers instead of maintaining bus lines.

Anyway, just wanted to tell you that you are DEAD WRONG, and you need to check your privilege! Have a great day!

That's some real talk about bus lanes and the traffic consequences of fewer roads. 

Dedicated bus lane sounds like a good idea.

As does providing fewer parking spaces than needed so the companies have to incentivize their workers. 

dedicated bus lanes don't mean shit unless there's grade separation... cars have to be prevented from casually using those lanes

also I think we're not only better off, but probably also our only choice, with all our eggs in the self-driving vehicle basket...

There is no reason that there could not be self-driving buses.

If there are already self-driving trucks...

...then self-driving buses seem inevitable.

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