Empirical flow modeling of urban arterial corridor for assessing flow improvement options

Abstract

Urban arterials mostly catering to through traffic are often bogged down with congestion resulting from minority crossing and right turning traffic. Introduction of signal free arterial with inclusion of over or underpass and grade separated U_loops may improve this situation. Evaluation of such scheme with data hungry micro simulation tools, especially in mixed traffic situation, is cumbersome and time consuming. Present study aims at developing an alternative evaluation tool based on empirical flow models. Here, corridor flow is modeled as a combination of link flow and intersection turn flow models. The widely used US BPR Link flow model and Webster traffic signal delay model are calibrated in this research using field data from Dhaka city arterial road. In the calibration process, Webster delay model is modified by estimating the parameters of third adjustment term in the delay model and the values of US BPR model using regression technique. The calibrated model is applied to evaluate recently proposed signal free Mirpur corridor arterial of Dhaka city and model estimation shows that about sixty percent reduction in existing travel time can be achieved through introduction of signal free arterial schemes. It is also found that signal free corridor benefit increases with increase in through traffic proportion. Sensitivity analysis of U-loop using the proposed spreadsheet based model shows that U-loop benefit erodes away with increase in U-loop spacing i.e. junction pair spacing. Again, U-loop results increasing travel time savings with increase in through traffic percentage. This research results will help developing the guidelines for transforming the busy signalized arterials into signal free arterials using low cost grade separation schemes as mentioned above.