Improving Driver Perception of Signals near Vertical Curves (0-4084-S)

Within the state of Texas, the standards and guidelines provided in the Texas Manual on Uniform Traffic Control Devices (TMUTCD) direct most of the decision making concerning the type and placement of roadside signing. However, there are some instances in which complexities of the driving environment indicate that supplemental devices be used even beyond those required and suggested by the TMUTCD. In the case where signalized intersections are located beyond crest vertical curves, the TMUTCD provides for upstream use of SIGNAL AHEAD text or symbolic advanced warning signing where the signal heads for the intersection are not visible for some minimum distance upstream of the intersection. However, the TMUTCD's placement distances of SIGNAL AHEAD advanced warning signs extend to only 650 feet (for a speed of 65 mph) from the primary traffic control device (i.e., the traffic signal). Therefore the possibility exists that even the advanced warning sign may not be fully visible to motorists approaching the intersection because their line of sight is limited by the vertical curve upstream of the signal. Also, the queue of vehicles from the signal may extend far enough back from the signal that even an advanced warning sign would provide insufficient notice to approaching motorist.