The (old) Licquia Family Blog
This is the old blog site, powered by a simple blogging system called Blosxom. It's here to keep old links from breaking, and for whatever historic interest might remain.
Here's the current site.
This is the old blog site, powered by a simple blogging system called Blosxom. It's here to keep old links from breaking, and for whatever historic interest might remain.
Here's the current site.
At least, if you believe CBS News, anyway. (Via InstaPundit and TheAgitator.)
How does it work? It's simple. A city installs red light cameras at intersections, which snap pictures of the license plates of cars that run the light. Anyone so snapped gets an automatic ticket. Then, when the city finds itself needing money, it reduces the duration of the yellow light. With a shorter yellow, more people who think they have time to make it end up entering the intersection a split second after the light turns red. That translates into more tickets (remember the camera taking pictures of light runners?), and thus more revenue. The trick seems to work better when the short yellow comes after a series of longer yellows, as was the case in the CBS story; people seem to think that all the yellows will be the same duration.
Let's do the math, shall we? 30 miles per hour translates to 44 feet per second. (30 miles/hr times 5280 feet/mile divided by 60 minutes/hour divided by 60 seconds/minute.) So, reducing the duration for the yellow light from 4 seconds to 2.7 seconds (again, from the CBS article) reduces the "stopping threshold" (the point before the intersection where you can't make it on yellow) from 176 feet to 119 feet, a difference of 57 feet. If we assume a reaction time to the yellow light of 1 second, that means that you have 75 feet to stop on the short yellow, as opposed to 132 feet on the regular yellow. If this site is correct, and it takes 45 feet to stop an average car at 30 miles per hour, that leaves a safety cushion of 30 feet, or about 0.7 seconds, on a short yellow, as opposed to 87 feet, or nearly 2 seconds, on a regular yellow.
(It's worth noting that the site above really thinks that a driver at 30 miles per hour needs 66 feet, or 1.5 seconds, to react, so the numbers are, if anything, generous. Math corrections are welcome in the comments.)
Now imagine someone following you at one car length (15 feet). If he's watching your taillights instead of the traffic signal, on the short yellow he gets 0.7 seconds to stop, which translates into 30 feet. Given the 45 feet he needs to stop, the extra 15 feet back he needs to be to give your car room, and his 15-foot cushion, that translates to -15 feet. One word: crunch.
The story above was from Maryland. Another example, in San Diego, is detailed in this Congressional testimony by the former mayor of San Diego regarding a similar system. In this case, hundreds of tickets were thrown out by a judge. It turned out that the contractor installing the cameras got a kickback for every traffic ticket, and had written a mandate against increasing the yellow light duration. This despite evidence that increasing the duration of the yellow light can dramatically reduce accident rates.
It's also interesting to note that the National Motorist Association is strongly opposed to red light cameras.
Jun 16, 2003 | Comments are no longer available