quote:
Originally posted by Tosh:
A couple of years ago, there was a suggestion in the local paper that a radar should cause traffic lights to turn red ahead of a speeder. I don't know what happened to that idea
After thinking about it: I expect they found out that traffic controllers just don't work that way.
There is no input that forces them to unconditionally turn red, except the preemption input and that turns EVERYTHING red except for the approach the preemption is from, which gets a green. That would really mess traffic up if they tried to use that to slow down speeders, not to mention that if they WERE using preemption for emergency vehicles it would result in big problems because only one approach gets a preempt at a time and all others are locked out.
Now, it is possible, I supose, if they're running a 170 or 2070 controller to use custom firmware to do what they want without having ot use the preempt input..but they would have to find someone to program it for them. (Generally, though, the only reason to be using 170 or 2070 controllers is if the signals are coordinated and having them turn red for speeders totally defeats the purpose of coordination).
NEMA controllers, the most commonly used type, don't have open architecture and therefore cannot have their firmware altered except by the manufacturer, so the preempt input is the only option for these.
If they're still using an electro-mechanical controller (and I somehow suspect that any place that would seriously consider turning the light red for speeders probably is still using one), they'll have to upgrade to modern signal hardware to get a preempt input, which costs real money for which they probably have more important things to spend it on.
