Actuated Signal Operations of Congested Diamond Interchanges

摘要

Actuated signal operations for congested conditions were evaluated with a simulation study at diamond interchanges. Both three-phase and four-phase with two-overlap phasing strategies were employed, with four ramp spacings and traffic patterns. The performance difference was discussed with throughput, average delay, and total stops. Results showed that four-phase control gave less or comparable average delay (or more throughput) for most traffic patterns at ramp spacings of 122 m or more. Three-phase control gave less delay (or more throughput) when an interchange had a balanced traffic pattern from all external approaches. In terms of stops, four-phase operation gave less stops than three-phase operation for all congested conditions investigated. Analysis results indicated that marginal operational benefits could be obtained when ramp spacing was designed between 122 and 183 m. In addition, several regression models were developed for use in performance estimation for congested traffic conditions. The test results showed that the models could provide good performance estimation of congested signal operation at diamond interchanges.