Supplementing signalized intersection infrastructure to provide automated performance measures with existing video detection equipment

The objective of this work was to retrofit a signalized intersection with the goal of developing event-based performance measures while leveraging existing infrastructure to its fullest extent. A TS1 intersection managed by the Arizona Department of Transportation in Flagstaff was chosen as the test location. In addition to video from the existing cameras, video detector interface cards were installed in the cabinet to provide contact closure outputs of vehicle flow rates. These outputs were then conveyed to an onboard event-based data logger within the traffic controller via TS2 communications. Performance measures were generated [volume-tocapacity (v/c) ratio and cumulative counts] from the video-generated data and compared with manually counted data over a 24-h analysis period. The v/c values generated by the video data were shown to be statistically different from those calculated with the manual count data; however, on all but one phase, the difference was not operationally significant. Analysis of cumulative count data showed operationally significant differences. A cost analysis determined that the price of equipping a similar intersection for this type of vehicle count capability is about $16,000 if the equipment specified for this project is used and if it is installed during the construction of the intersection. It is recommended that jurisdictions interested in developing this type of flow information consider equipping future intersections in a similar manner and that future work be completed in the evaluation of the use of video detection units for flow rate collection at signalized intersections.