This is a continuation of the earlier post on detection diagnostics, at:
http://ntcip-unleashed.blogspot.com/2012/02/controller-detection-diagnostics.html
The detector settings need to be reviewed to make sure that the global settings are not creating undue consequences.
In one recent example, a left turn pocket had moderately high traffic volumes, and the stopbar detector was a 60-ft long quadrapole. The length of the quadrapole created a situation where there was never a gap in the traffic, so the standard stopbar (standing queue expected) timing of 5 minutes max time / 10 seconds detector fail time, created a situation where the timer for the left turn signal gapped out cycle after cycle.
This was not a new signal, but one where the operation had been changed from one brand of signal to another brand of signal as a part of a systemwide upgrade. The settings were consistent with the previous brand's operation, but some changes were made in the conversion.
In looking at the new operation, it appeared that the signal was gapping out consistently, but there was a static queue forming. The signal was gapping out because the detector fail mode was only placing a call for 10 seconds, and if the traffic was over the advanced detector, then the siganl would extend for time beyond the 10 seconds.
After observing the operation for a short while, it was apparent that the signal was not getting enough time for the movement. Determing the reason for this operation was complicated by the fact that the 60-ft quadrapole also had NTCIP Queue mode turned on.
The detector diagnostics operate on the raw feed of the detector into the controller, not on the processed controller operations of the detector.
After observing the left turn pocket's operation via video feed, some modifications were made to the detector diagnostics from 5 minutes max time / 10 seconds detector fail time, to 15 minutes max time / 20 seconds fail time.
Once the timing changes were made, the left turn pocket cleared out in a few cycles, and began operating as expected.
The moral of the story is that the signal operation needs to be monitored after changes are made.
http://ntcip-unleashed.blogspot.com/2012/02/controller-detection-diagnostics.html
The detector settings need to be reviewed to make sure that the global settings are not creating undue consequences.
In one recent example, a left turn pocket had moderately high traffic volumes, and the stopbar detector was a 60-ft long quadrapole. The length of the quadrapole created a situation where there was never a gap in the traffic, so the standard stopbar (standing queue expected) timing of 5 minutes max time / 10 seconds detector fail time, created a situation where the timer for the left turn signal gapped out cycle after cycle.
This was not a new signal, but one where the operation had been changed from one brand of signal to another brand of signal as a part of a systemwide upgrade. The settings were consistent with the previous brand's operation, but some changes were made in the conversion.
In looking at the new operation, it appeared that the signal was gapping out consistently, but there was a static queue forming. The signal was gapping out because the detector fail mode was only placing a call for 10 seconds, and if the traffic was over the advanced detector, then the siganl would extend for time beyond the 10 seconds.
After observing the operation for a short while, it was apparent that the signal was not getting enough time for the movement. Determing the reason for this operation was complicated by the fact that the 60-ft quadrapole also had NTCIP Queue mode turned on.
The detector diagnostics operate on the raw feed of the detector into the controller, not on the processed controller operations of the detector.
After observing the left turn pocket's operation via video feed, some modifications were made to the detector diagnostics from 5 minutes max time / 10 seconds detector fail time, to 15 minutes max time / 20 seconds fail time.
Once the timing changes were made, the left turn pocket cleared out in a few cycles, and began operating as expected.
The moral of the story is that the signal operation needs to be monitored after changes are made.
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