Thursday, November 19, 2009

four way stops

Another chapter in the "Berkeley City Planning Is Stunningly Misguided" series: Four way stops.

Everyone knows the costs and benefits of a single isolated four way stop. In very dangerous intersections, it can reduce accidents. In an intersection where one direction is very busy and the other busy enough to have backlogs that can't get through, or in a busy intersection where pedestrians rarely have a chance to cross, it can improve traffic flow. On the downside, both of those things are better accomplished with intelligent stoplights, which don't cause backlogs of traffic waiting for each individual car to stop and then proceed. And they cause delays and waste fuel. And they are essentially impossible to remove once built, since drivers become accustomed to cross-traffic having to stop.

But there's an ignored cost of having a large percentage of four way stops in an area in general, and I'm surprised I can't find any studies that quantifies. In the few normal two-way stops in low traffic areas, the car that has to stop expects cross-traffic to stop as well and often cuts them off, resulting in many near-accidents. This is the issue in Berkeley, where almost all residential intersections are four-way stops. (I've almost been hit twice this way and now habitually slow down if there's anyone waiting at stop sign even when I don't have one.)

Of course, now that they've implemented such an insane system, it's basically impossible to undo. But since all of these four-way stops are in low-traffic residential neighborhoods where they are entirely unnecessary, and they increase danger in two-way intersections, I'm guessing they make the city more dangerous on net, on top of the time and fuel wasting. Good job, city planners.