GeekLimit

E-Z Pass and basic math used to catch speeders?

Posted by The Technocrat | Filed under Geeky, Home & Auto

Traffic/Congestion Monitoring
I'm sure this will be IDOT's excuse for installing more of these. This is completely bogus, since there are already thousands of sensors buried in the roadways that can accurately record traffic conditions. Here is a great implementation of the usage of these sensors, which update every few seconds. Unfortunately for IDOT, this doesn't give you any personally-identifiable information about the motorists.

Speed Traps
By taking the distance between the sensors (let's say a half-mile) and taking the posted speed limit (let's say 60 miles per hour), IDOT knows that it should take you exactly 30 seconds to get from sensor to sensor. If you got there in 25 seconds, they can figure out (via basic math) that you were doing 72 miles per hour.

Now I'm not saying that catching speeders is wrong. The speed limit, however wrong that may be, is still the law. The debate as to safety vs. speed limits could go on forever, and it's widely known that there are much less speed-related problems on the interstate than on the streets.

Anyway, my problem is with forcing people into the system by jacking up tolls, knowing that you're going to turn it into a speeding-ticket revenue machine in the near future, and all the while saying that you're not going to use it for that exact purpose.

In addition, the half mile laid out on I-355 is prone to errors. People stopping at the booth would be able to accelerate all the way to the 75th street overpass, exceeding the speed limit, since their average speed would stay below the limit.In effect, starting from 5 mph at the toll booth enables them to basically 'earn' the right to speed later by going below the limit while leaving the toll plaza.

Also, the distance between the sensors is prone to errors. Just one second of delay with either sensor reading (or if one sensor is off by one second compared with the other) would make a computing error of 2.4 miles per hour. (if we used the example data above)

In additon, you're allowed to have multiple cars listed for each transponder. If the transponder doesn't register, the camera looks up your plate # and bills your account. No account, and you get a ticket. So what's stopping someone from registering a second car on their transponder, then taking the car, blasting through the first booth, and throwing the transponder under the seat for the second? The first booth sees the transponder, the second sees the plate#. Pretty sure the camera isn't being used for every car, just the ones that don't register when they drive through…

All in all, these sensors seem to be in the testing phase for catching speeders. Due to the problems I list above, anticipate trying to explain yourself when errors occur, and still being fined because you couldn't explain it in simple-enough terms to your state's EnforceBot.

Also, if you don't live in Illinois, don't laugh. It'll come to you soon enough.

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Comments (0) | May 2nd, 2006