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Transportation Science

Unintended Consequences For Traffic Safety Feature 579

An anonymous reader writes: Traffic engineers had a problem to solve: too many pedestrians were getting hit by cars while using the crosswalks at intersections because they didn't know when the 'WALK' sign would change. Their solution was simple: implement a countdown timer. Countless cities have now adopted these timers, but it turns out to have an undesired consequence: motor vehicle crashes are actually increasing at intersections where the countdown timer is used. Researchers think this is because pedestrians aren't the only ones who see the timers. Drivers see them too, and it provides them with information on when the light will change. Then they anticipate the change by either speeding up to beat a change to red light, or anticipating a green light in order to get through before the pedestrians can move into the road. The researchers suggest finding some way to hide the countdown from the drivers, perhaps through the use of an audio countdown that would be difficult to hear from inside a car.
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Unintended Consequences For Traffic Safety Feature

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  • Driverless Cars (Score:5, Interesting)

    by mfh ( 56 ) on Wednesday July 02, 2014 @08:22AM (#47367487) Homepage Journal

    Computers will fix this kind of thing by default.

  • by McGruber ( 1417641 ) on Wednesday July 02, 2014 @08:26AM (#47367527)
    Sacha Kapoor and Arvind Magesan, the authors of the paper, are economists. Slashdot: How Often Do Economists Commit Misconduct? [slashdot.org]
  • Cali... (Score:5, Interesting)

    by bswarm ( 2540294 ) on Wednesday July 02, 2014 @08:29AM (#47367545)
    In Ca, it's a ticket if a car enters a crosswalk while a pedestrian is using it, no matter if they're on the other side of the intersection or not. And the new walk signals have a visor around them so unless you're almost directly in front of it, you can't read it. They also started using audio signals, which beep and talk, for the blind.
  • by KingOfBLASH ( 620432 ) on Wednesday July 02, 2014 @08:31AM (#47367561) Journal

    ...is they try to fix human behavior via engineering, but people can't really be engineered.

    For example, in my home town we had a roundabout from hell. Five highways came into a loop via offramps. Literally once a week there would be an accident and once a month it was a fatal one.

    So some brilliant traffic engineers tried to solve the problem by creating off ramps for each other highway. At highway A you could choose to offramp to highway B, C, or D. But the "offramps" used the roundabout, which now had concrete dividers about curb height. The mayor, the local press, and local government kept trumpeting how many lives this would save.

    Well, turns out the only thing more dangerous then five highways going into a giant roundabout is five highways going into a roundabout with concrete dividers to slalom around. Accidents became a daily occurrence and fatalities went up.

    As it turns out, people are stupid. Sure, if you are new to town and take the time to slow down to read the sign, and drive carefully, you can figure out where you're going. But people zip in at highway speeds, apply the brakes quickly, and try to swerve over.

    The problem is not one of engineering, but one of behavior. Modifying the behavior (via police enforcement) would be more effective then a fancy solution.

  • Re:sound and sides (Score:5, Interesting)

    by Sockatume ( 732728 ) on Wednesday July 02, 2014 @08:34AM (#47367579)

    A lot of crossing signs in the UK have metal boxes around the lights, and horizontal shutters to boot, so you can't really see the light from anything but ground level at the crossing point. I'm guessing it's largely a light pollution and confusion-reduction measure (e.g. you don't see the light for an adjacent crossing and mistake it for your own) but it means that the hardware's already available, probably as an off the shelf component, for some styles of light.

  • Shared space (Score:5, Interesting)

    by Hypotensive ( 2836435 ) on Wednesday July 02, 2014 @08:55AM (#47367723)

    A better solution might be to remove the signals altogether. Several European towns have tried shared-space experiments where there are no signals or markings and the pedestrians and vehicle drivers have to actually watch out for each other. In all such experiments so far, traffic fatalities have dropped significantly.

  • by Anonymous Coward on Wednesday July 02, 2014 @09:14AM (#47367863)

    The most dangerous place to cross a street is at an intersection. Pedestrians have to look in 4 different directions to be sure no cars are going to hit them. Drivers have to consider the same 4 directions. But if you walk across the street half way between intersections, then you only have to consider cars coming from TWO directions. I did the math, and that's half as many ways you have to look.

    As a pedestrian who nearly got hit recently (while crossing at an intersection, WITH a walk signal--and yes, I took the initiative and moved out of her way before she hit me), this has seemed obvious for quite a while now. I will admit that if we made this official, it would cause more work for drivers, as they would have to be on the lookout in twice as many places. But it beats getting hit.

    Think of it this way: It's not jaywalking, it's civil disobedience! There, much more amenable to slashdotters! 8-)

  • by GbrDead ( 702506 ) on Wednesday July 02, 2014 @09:20AM (#47367891)

    Here in Bulgaria we have many (in fact, most) traffic lights with countdown timers for cars. Most don't even have timers for pedestrians. And these timers started to appear about ten years ago.
    I haven't heard of increased car crashes at intersections. My own observations also don't point in this direction. People are (or at least I am) using these timers as a more precise yellow light. And drivers in Bulgaria don't have to twist their necks in order to see them. Maybe this is the problem?

    Disclaimer: Bulgaria has a very high fatality rate on intercity roads. These are not related to traffic lights, though.

  • by cloud.pt ( 3412475 ) on Wednesday July 02, 2014 @09:23AM (#47367911)

    In some areas of Portugal we have exactly the opposite - timers applied to traffic lights instead of crosswalks. In some places we also have crosswalk timers together with traffic light timers.

    Why is this a solution? Because drivers will stop paying attention to crosswalk timers and use their own traffic light timers instead, which have a security offset of 1-3 seconds. This not only makes standing at a traffic light much more dynamic and time-efficient (drivers will know how long they have to do imprudent things like fixing a rear glass, looking at the mirror, texting or picking something out of a glove box, with a high degree of safety), but it also prevents them from prematurely hitting the gas, as most drivers feel it is unsafe to go before the timer hits 0.

    Also, the timer works in both waiting for a green and waiting for a red. Yellow lights could be fully substituted by a red and green light only with a timer which would turn yellow on the last 1-3 seconds before a red. It would also prevent a lot of ambiguity in yellow light ticketing which is very common in urban areas and is reason for dispute between veteran drivers and over zealous traffic authorities.

  • Re:OR (Score:5, Interesting)

    by drerwk ( 695572 ) on Wednesday July 02, 2014 @09:48AM (#47368065) Homepage

    One could argue that in most cases, a pedestrian paying attention could have avoided getting ran over if they'd pulled their heads out of their phones long enough to look around them.

    SFPD claims to be keeping better stats these days but I could not find them online.
    However here is what I did find: http://www.ktvu.com/news/news/... [ktvu.com]

    All three victims this year entered the crosswalk only after pushing a button to activate several flashing beacons to alert drivers to stop. There are six lanes of traffic across Sunset with an island in the middle. Thursday's crash occurred when several drivers stopped, but a Honda CRV kept going. The driver noticed the woman too late and skidded into her, clipping her with the front bumper and spinning her to the pavement. "She said she didn't see her, " San Franicsco Police Officer Gian Tozzini told KTVU. "I don't know how she didn't see the flashers. Maybe they're just looking forward and not paying attention."

    That is three victims, one fatally injured, at a single crosswalk with flashing lights in the Sunset. The description matches what I see in my little New England town where I'll slow because I see a deer stepping into the road and the car behind me thinks they need to pass me on a two lane road so as not to slow down at all - not sure how bad I'd feel other than for the deer. A pedestrian was hit in our crosswalk same way - one car stopped, person started walking, car behind did not even slow down and passed in the next lane hitting the person in the crosswalk - actually tossing them into the front window of another car that had also stopped on the other side for the pedestrian - that car was full of kids coming home from little league.

  • subject (Score:4, Interesting)

    by Charliemopps ( 1157495 ) on Wednesday July 02, 2014 @10:26AM (#47368403)

    Not all crashes are created equal. Simply stating "Crashes increased" means nothing. Scratched paint? Were they fatal? The perfect example are roundabouts. When they were introduced in the US years ago, the number of accidents in those intersections actually increased rather dramatically. People were up in arms, but then the statistitions came out and explained that while the number of accidents increased, they were on average far more minor incidents. Mostly side swipes and such. It was damned near impossible to get into a fatal car crash in a roundabout. Compare that with our old red light system where accidents are very often bad enough to total both cars and are frequenty fatal and suddenly that increase in total accidents doesn't seem so bad.

  • Re:OR (Score:2, Interesting)

    by Anonymous Coward on Wednesday July 02, 2014 @10:35AM (#47368509)

    There's a solution for this. Confiscate cars when people are driving recklessly. Drunks, in particular. The "destroy a white collar career, minimally affect those on welfare, and it's just a lawyer bill to the rich" penalties for DUI are stupid. If you're driving in a manner that can kill someone, among other things, your weapon should be confiscated. Just like guns and knives, except the part where cars are much more deadly than guns and knives.

  • by Anonymous Coward on Wednesday July 02, 2014 @10:53AM (#47368645)

    Please don't use audio count-down. There is too much irritating noise pollution in our cities at night. There is no point in having audible signals making noise 24/7 if there is no one there to hear it most of the time.

To write good code is a worthy challenge, and a source of civilized delight. -- stolen and paraphrased from William Safire