6 ms·

Networked traffic routing apps like Waze ought to nullify the Braess' paradox; if everyone used Waze, new roads would always have a positive marginal impact.

• stuaxo 11y ago
  In London they are proposing to build new tunnels under the Thames which will could massively increase traffic in east London. Whether traffic moves faster or slower pollution is bound to increase.
• gizmo686 11y ago
  That only works if the app is willing to give individuals sub-optimal paths in order to optimize total performance. If that is the case, then an individual has incentive to not listen to the app.
  • matthj 11y ago
    Unfortunately, Waze has at least two incentives not to provide socially optimal paths. First, individuals would have an incentive to find individually-optimal paths by using a different app that provides them. Second, it seems likely that more people turn Waze on when traffic is bad, so social suboptimality might actually be good for Waze. On the other hand, with socially optimal traffic patterns there would be induced demand and more drivers would come on the roads and potentially use Waze. It's actually difficult to know what would make Waze better off, providing socially optimal routes or individually optimal routes. Waze might also behave like many companies and ask for subsidies from local governments for turning on the social optimization, and the local governments are ill-equiped to know how much to pay.
    • benbou09 11y ago
      If driverless cars always for go for the most favorable route for them, they might increase traffic a lot. Fortunately, it is also probably easier to force computers than people to follow socially optimal routes.
      • eru 11y ago
        Especially if there's a way to redistribute the social gains.
  • deleted 11y ago
    [deleted]
• pash 11y ago
  The situation is complicated by induced demand [0], the phenomenon in which providing more roadway capacity tends to raise demand for it by reducing the cost of travel. What typically happens when a new roadway opens or a congested route is widened is that travel times first fall, as expected; but soon the reduced travel times attract drivers who previously had used other routes, or who had commuted at off-peak times, or who had used public transit. Thus the improved roadway ends up with significantly more traffic than the old roadway, and the price (in travel time) of the increased capacity is bid back up near its previous level. Added roadway capacity can lead to a welfare improvements, but it mostly comes in the form of fewer people shifting their schedules to beat rush-hour traffic or deigning to take public transit, and not through reductions in travel times. In actual fact, as we've seen throughout the era of American suburbanization, vast new roadways have probably substantially increased average travel times [1] by markedly changing patterns of land use (i.e., by giving rise to the modern low-density, car-dependent suburb), albeit while also engendering some welfare gains (e.g., increased suburban living space). If you want to prevent induced demand from gobbling up expected improvements in travel times when you build new roads, you pretty much either have to (a) decrease demand by deliberately increasing the financial cost of travel (e.g., through tolls or congestion charges), or (b) over-build roadway capacity in the extreme, to the extent that just about everyone in the region can fit on the roads at once, alone in his or her own car (as is the situation in cities like mine). 0. https://en.m.wikipedia.org/wiki/Induced_demand https://en.m.wikipedia.org/wiki/Induced_demand 1. I mean in comparison to a counterfactual alternative history in which the urban-suburban commuter freeway systems typical of American cities went unbuilt. Commute times in European metropolises, which mostly lack the extensive commuter roadways and concomitant suburban sprawl of their American counterparts, are broadly lower than in American metros of similar sizes, for example.
  • sandworm101 11y ago
    That is true if the new road does is indeed the source of the new traffic. But it all falls apart if that future increase in traffic will be coming regardless of whether the road is built. that's where the paradox really breaks down. You cannot solve the problem of an external source of new traffic, be it a new stadium at the edge of town or new machine added to the edge of a network, by not building in any new capacity. Well, you could if you simply chose not to serve that new node. Not running any new roads to a new airport is a great way to get that airport to close, just as not serving that new customer on your network is a great way to make that customer go elsewhere. The other flipside to the pardox is that it really is applicable to any network. Sometimes the best way to improve the efficiency of mass transit is to cull bus/train routes. But try selling that in a modern city.
• reddytowns 11y ago
  If you believe that, then you don't understand Braess' paradox.
• oceanpumpkins 11y ago
  Does Waze optimize for the socially optimal distribution over the whole network, or does it optimize for each individual traveller? If it optimizes for each individual traveller, then Braess' paradox still applies even with Waze because all the travelers in Braess' paradox make the individually optimal choice. If it optimizes for the socially optimal distribution, then it does solve the problem. But this sounds like an optimization problem that would be really hard to formulate and solve in practice, so I'd be surprised if Waze (or any other networked traffic app) did it right now. Maybe eventually?
• abhgh 11y ago
  I wonder how a route suggesting app, that accounts for traffic, avoids the El Farol Bar (lets call it EFB) problem. EFB essentially is people in the town of El Farol want to have a good time, and they the option of staying at home or going to the one bar the town has. If a lot of them end up at the bar, people would have had a better time staying at home. And if a lot of them stay at home, the bars are not crowded and they'd have had a better time in the bar. The catch is no one knows in advance who is going to go the bar. It can be shown that no pure strategy can work for EFB.
  • micwawa 11y ago
    "Nobody uses pure strategies anymore. They're too popular" - Yogi Berra