Evaluation of Adaptive Signal Control Technology—Volume 1: Before-Conditions Data Collection and Analysis

Field evaluation of adaptive signal control technologies (ASCT) is very important in understanding the system’s contribution to safety and operational efficiency. Data were collected at six intersections along the Neil Street corridor in Champaign, Illinois, before deployment of SynchroGreen, an ASCT system. The field delay and queue length for “before” conditions were measured and compared with estimates from the Highway Capacity Manual (HCM). The HCM estimates of stopped delay were significantly different in 58.3% of the cases, representing overestimation in 73.5% and underestimation in 26.5% of the cases. On major streets of typical intersections, in 72% of the cases, there were significant differences between HCM delay and field data; in 91% of the cases, HCM overestimated delay by an average by 69%. On the minor streets of typical intersections, in 56% of the cases there were significant differences, and in 94%, the HCM overestimated the delay on average by 52%. The HCM estimates of 50th-percentile queue length were significantly different in 61% of all cases, including overestimation in 56% and underestimation in 44% of the cases. For typical intersections, 52% of the cases had significant differences, including overestimation in 93% and underestimation in 7% of the cases. On the major streets of typical intersections, 68% of the cases had 50th percentile HCM queue lengths similar to those from the field. However, in 28% of the cases it overestimated the queue length on average by 66%; and in 4% of the cases it underestimated it on average by 42%. For minor streets of typical intersections, in only 25% of the cases were the HCM queue lengths similar to those from the field; in 70% of the cases, HCM overestimated the queue length on average by 44%, and in 5% of the cases, HCM underestimated it on average by 20%. In general, it was observed that the trends in the 50th- and 95th-percentile queue length comparisons supported each other. Also, in 91% of the cases, the trends in delay and queue comparisons were either consistent with each other or did not have any significant conflicts. However, in 9% of the cases, significant inconsistencies in trends were observed. Thus, to save time, one may compare the HCM queue length estimates to field data to assess intersection performance, though the delay comparison is preferred.Illinois Department of Transportation, R27-127Ope