Assessing deterioration of pretimed, actuated-coordinated, and scoot control regimes in simulation environment

Regular updating of traffic signal timing plans is very important for successful traffic control. However, many jurisdictions fail to update signal timings because it is labor intensive and costly. Without updating, signal timings become obsolete as traffic volumes change. Adaptive traffic control is sometimes perceived as a way to avoid retiming traffic signals. There are no findings that support this belief.; This research investigates the deterioration of pretimed, actuated-coordinated, and SCOOT traffic control regimes through the use of microsimulation. Deterioration of actuated-coordinated and SCOOT adaptive controls have not been investigated before. Previous attempts to investigate the deterioration of pretimed control did not use microsimulation. Two major objectives of the study were to develop a methodology to assess the deterioration of the traffic control regimes through microsimulation and to evaluate the deterioration of the traffic control regimes with respect to modeled changes in traffic demand and distribution.; The experimental nine-node grid network is used as a test bed to model deterministic and stochastic traffic demand and distribution changes in link flows. Traffic signal plans developed for the base traffic conditions serve as the non-optimized plans for all other conditions. Optimized plans are developed for each scenario of changed traffic flows using macroscopic optimization tools.; The results show that all traffic control regimes deteriorate. The results for pretimed and actuated controls show that there is a benefit of up to 3% for up to 5% of uniform growth in traffic demand for networks with unchanged traffic distributions. When stochastic variations of traffic demand and distribution are introduced, the benefits rise to an average of 35% for pretimed control and 27% for actuated control. Assessment of SCOOT ageing shows that SCOOT performance highly fluctuates with changes in traffic flows. The SCOOT control performs worse than optimized pretimed control for most of the scenarios. Had the SCOOT control been replaced by optimized pretimed plans, benefits of 11 to 16% could be achieved. The roots of SCOOT ageing have been found in its inability to accurately model traffic at the intersection approaches for changed traffic flows.