Evaluation of Detector Placement for High-Speed Approaches to Signalized Intersections (7-3977-1)

The primary objective of this research was to validate the new TxDOT procedures for loop detector placement on high-speed approaches to signalized intersections. The study approach involved conducting a field study at selected sites to compare the proposed new loop configuration to the existing configuration. The data analysis included investigating approach speeds to the intersection, driver actions in response to a yellow indication, and vehicle location at the onset of yellow.Results from the field study revealed that the new loop configuration is as good as, and in some cases better than, the old loop configuration. Because the new loop configuration can detect vehicles further upstream from the intersection (at the beginning of the dilemma zone), it results in fewer vehicles being caught in the dilemma zone at the onset of yellow. The new loop configuration resulted in fewer vehicles running the red light, a major cause of accidents. Also, because the new loop configuration typically resulted in more vehicles using the yellow light instead of stopping, fewer rear-end accidents may result.