In 2007, the Dutch city of Drachten did away with street lights in 20 four-way intersections, installing traffic circles instead. The shift caused a dramatic decline in the number of traffic-related deaths: one intersection went from 36 in the four years before the shift to two the year after. And vehicles now cross the junction 20 second faster.I hesitate to generalize from a small sample, but a few days ago a traffic light with a 90 second cycle was on the blink. That 90 second cycle includes the left arrow, common in Illinois. A lot of cars can back up in 90 seconds, particularly if the left arrow is in effect for the better part of a minute itself. But cars don't arrive at that corner in packs because these aren't the busiest streets in town, and because it isn't near a shopping center with its out-of-synchronization access signals that generate packs of traffic. So when the light is on the blink, drivers treat the flashing reds as a four-way stop, and with relatively infrequent arrivals of cars at the corner, wait times are a few seconds instead of up to two minutes. Something similar might be at work to the advantage of drivers arriving at those Drachten rotaries.
"The idea is to create space where there is mild anxiety among everyone so they all behave cautiously. No one thunders along at 30mph on a high street thinking that they have priority," Owen Paterson, the Dutch Transport Minister, told Jalopnik. "Instead of the State laying down the rules, we need to give responsibility back to road users."
A related article notes that there is a right way and a wrong way to time the traffic lights, in those areas where the traffic might be heavy enough to require signalling.
David Goldberg of Transportation for America says timed signals can be dangerous if they encourage drivers to speed through lights, and force pedestrians to wait too long for an opportunity to cross. He, like Flocks, is an advocate of systems like HAWK, which empower pedestrians to cross safely.Those lights that favor the speeders are probably accidentally timed, if at all. There used to be several stretches of Warren Avenue in Detroit that somebody going 40 or faster could get a green at Grand and sail all the way to Wayne State without stopping, while somebody obeying the posted 30 (never enforced, even in those days) would encounter reds at each controlled corner. I encountered a stretch of U.S. 1 from Trenton to New Brunswick where I in my rental car was behaving myself and the locals were going 65 to 70 and making all the greens while, once again ...
Flocks says timed lights can work if they're used correctly. She warns against systems that encourage drivers to speed up to get through as many lights as they can.
But some lights are designed to incentivize the opposite, she says. The key is the timing. If traffic lights are designed so that you have to speed a little to get through them all, then that's what drivers will do. But some cities have a system in place that punishes speeding drivers. Drivers going five to ten miles over the speed limit are stopped every third light. If you're going exactly the speed limit, you'll cruise down the road.
Pedestrians are likely to be safer if the engineers make the effort to time the greens to encourage adherence to the speed limit, rather than putting signals in haphazardly with speeding-encouraging patterns that regular drivers discover.