By John Carr, NMA Massachusetts Activist
“Damn the torpedoes. Full speed ahead!” — Admiral David Glasgow Farragut
Unreliability and you
Suppose you hit a red light and it never turns green as long as you wait. You can sit there forever, or you can run the red. A ticket will be in the mail.
You see a yellow and decide you can beat the red. You cross the stop bar, the camera flashes, and a moment later the light turns red. Ticket in the mail, even though the red light wasn’t on when you entered the intersection.
Traffic signal standards let this happen. Vehicle detectors only need to be 98% accurate. They can ignore you once a week and leave the light red. Light bulbs can take hundreds of milliseconds to turn on. The controller thinks it lit a red light before you entered the intersection, but the light didn’t turn red until you were in the intersection.
The specifications were fine decades ago when humans enforced traffic laws. If a cop was watching the intersection he might wave you through when your light failed to turn green. He wasn’t out to write tickets when the race between red light and car ended in a tie.
Robots have no such judgment or mercy. With cameras, lax standards are like a mine waiting to go off.
Is two percent a lot?
Detector failure rate came up during a discussion of intersection conflict warning systems (ICWS). These are flashing lights to warn of cross traffic at a two way stop intersection on a high speed road.
If drivers learn to rely on the flashing light and it fails, somebody is liable to be hit broadside at 60 miles per hour. Engineers don’t like failure modes that put people in danger. A 2% detector failure rate could be a fatal flaw, literally and figuratively.
Fortunately most new hardware is better than standards require. Vehicle detectors see over 99.9% of cars. Traffic safety researchers are studying whether detectors are good enough to avoid crashes. But they aren’t studying whether detectors are good enough to avoid tickets.
Who makes the rules for making the rules?
A few months ago I remarked that the average city engineer is not an expert on the science behind speed limits and stop signs. Posting a thousand signs does not teach you anything about when speed limits improve safety.
There are experts on the effects of traffic control devices. (Some of them are also city traffic engineers.) They figure out if ICWS works, how many crashes justify a stoplight, and so forth. Some of them belong to the National Committee on Uniform Traffic Control Devices. The NCUTCD has a strong influence on traffic control standards. If it says yellow lights should be at least four seconds long, or painted wood signs are appropriate in parks, the Federal Highway Administration will give serious consideration to the proposal.
The National Motorists Association sent a couple observers to the NCUTCD meeting in Portland, Maine, recently. Issues related to ticketing and traffic enforcement aren’t on their minds. They aren’t worrying about how traffic control devices lead to traffic tickets. It’s not that they don’t understand, but they have to be prompted to think about it.
Slowly evolving standards
Vehicle detectors are more reliable than they used to be. LED signals turn on faster than old fashioned light bulbs. Neither improvement is mandatory. Electrical standards still allow the signal to ignore you occasionally and the red bulb to hesitate.
Not only equipment standards are waiting to trap you. How long should a yellow light be? The rules say between 3 and 6 seconds. Longer for higher approach speeds. Whatever that means.
So the department makes up a number. What if it’s too low?
Sometimes badly timed signals cause accidents. Responsible DOTs adjust signal timing. Others ignore wrecks because their computer says crashes shouldn’t happen.
The rest of the time, drivers learn to compensate. I know to look left before starting across Route 62 because either the yellow or all red interval is too short. The technical violation rate is high.
Timing rules are also waiting to blow up. Not only because they turn badly designed intersections into revenue. When aggressively enforced, short yellows become much more dangerous. Drivers pay attention to the signal instead of other traffic.
The people who make standards are not thinking about tickets, and that shows. Camera companies are rushing to exploit their narrow focus.
During the Battle of Mobile Bay Admiral Farragut cried “damn the torpedoes” and sent his fleet through a minefield. He got lucky. The fuses failed.
The traffic enforcement business is pushing us full speed ahead into the minefield left by lax standards. Our wallets and lives may not be as lucky as the Union fleet. We need to take a hard look at how traffic signals are designed and operated.