Research Report on Improving Diamond Interchange Operations Using Advanced Controller Features

Most modern traffic signal controllers contain "advanced" features that are often not used but may improve traffic operations under certain conditions. This report documents the research conducted in investigating how diamond interchange operations can be improved by using advanced controller features. The project evaluated the features of traffic signal controllers meeting the current TxDOT traffic signal controller specification. The effectiveness of the advanced features provided by these controllers was evaluated using traffic simulation with real traffic control hardware. Eight potentially useful controller features were identified: (1) separate intersection mode, (2) diamond phasing sequence change by time of day, (3) conditional service, (4) dynamic maximum green times, (5) dynamic split, (6), volume density control, (7) alternate maximum green and passage times, and (8) adaptive protected permissive left turns. The research addressed the applicability of these features under different geometric and demand conditions and investigated the effect of detector technology and human factors issues on implementation. Guidelines for improving diamond interchange operations using advanced controller features are included in the report as an Appendix. The Appendix describes the concept of operation of each feature and then provides detailed application guidelines, including applicability under different geometric and demand conditions, as well as compatibility with various detection technologies. Programming instructions are also provided.