stupid traffic light programming
PostPosted:Fri Dec 02, 2011 2:49 pm
There's a major road at where I go to work that's in a T junction area. Most of the traffic is on the horizontal section of the T with relatively little traffic from the vertical section and little traffic turning into the vertical section. On the main road there are only two lanes each way. It used to be the case that opposing lane has a left turn only lane as one of their two lanes (turning into the vertical section of the T), so this means opposing traffic only has one lane to use for going straight, which is the majority of the traffic, so the opposing traffic usually is pretty slow since they can only use one lane for the bulk of the traffic.
So someone got the great idea that the second lane should be a straight/left turn. Of course, given the volume of the traffic there is no way you can make a left turn without a left turn signal. However, I'm pretty sure the length of the left turn signal is done by your standard 'smart' sensors, i.e. if there are still cars in the lane then the left turn signal stays there.
So what happens is that the opposing traffic has left turn basically FOREVER since this is a high traffic area, so presumably there is always a car in the left turn lane which may not even turn left (in fact most of them move forward), and the forward traffic is perpetually stuck. I was timing the traffic and the opposing traffic has 1 minute of left turn signal, followed by about 25 seconds where the forward direction can actually move forward. So now in this one mile stretch near the T junction, it takes something like 30 minutes get past the T junction.
But it doesn't end here. Someone must have been complaining about the opposing traffic having a protected left turn signal for too long, so what happens? The forward traffic now gets a protected left turn timer to balance it out, except turning left in the forward direction takes you straight into a wall. I was watching this morning and noticed that my lane (the opposing traffic) isn't moving (red light), but the forward traffic is (green light). The traffic on the vertical section cannot move aside from a right turn (which they realistically can never do given the traffic volume anyway). So to make up the fact that one side gets hold up needlessly, the solution is to hold up the other side needlessly too. As I drove fast I noticed the forward section still has a ton of cars piled up since the opposing traffic still gets its 1 minute+ of protected left turn, but now we get to suffer some (though not as much) in case someone in the forward traffic wants to ram their car into the wall out of frustration.
So someone got the great idea that the second lane should be a straight/left turn. Of course, given the volume of the traffic there is no way you can make a left turn without a left turn signal. However, I'm pretty sure the length of the left turn signal is done by your standard 'smart' sensors, i.e. if there are still cars in the lane then the left turn signal stays there.
So what happens is that the opposing traffic has left turn basically FOREVER since this is a high traffic area, so presumably there is always a car in the left turn lane which may not even turn left (in fact most of them move forward), and the forward traffic is perpetually stuck. I was timing the traffic and the opposing traffic has 1 minute of left turn signal, followed by about 25 seconds where the forward direction can actually move forward. So now in this one mile stretch near the T junction, it takes something like 30 minutes get past the T junction.
But it doesn't end here. Someone must have been complaining about the opposing traffic having a protected left turn signal for too long, so what happens? The forward traffic now gets a protected left turn timer to balance it out, except turning left in the forward direction takes you straight into a wall. I was watching this morning and noticed that my lane (the opposing traffic) isn't moving (red light), but the forward traffic is (green light). The traffic on the vertical section cannot move aside from a right turn (which they realistically can never do given the traffic volume anyway). So to make up the fact that one side gets hold up needlessly, the solution is to hold up the other side needlessly too. As I drove fast I noticed the forward section still has a ton of cars piled up since the opposing traffic still gets its 1 minute+ of protected left turn, but now we get to suffer some (though not as much) in case someone in the forward traffic wants to ram their car into the wall out of frustration.