A major tool available to traffic professionals to ensure optimal use of the available road capacity on urban arterials is the use of traffic signals at road intersections. Most of the conventionally used traffic signal control strategies are developed for traffic conditions which are predominantly Homogeneous and Lane-Disciplined (HoLD). The traffic in most developing countries is characterised by a large diversity in the types of vehicles present (heterogeneity of vehicle types) - and lack of lane-based traffic flow. Despite these major differences in traffic conditions, guidelines in most developing countries either recommend using conventional signal design strategies or base their design guidelines on signal design strategies adopted in countries with HoLD traffic conditions (IRC: 93 1985). This results in inefficient operation of traffic signals in traffic streams with Heterogeneous and Less-Lane-Disciplined (HLLD) traffic conditions. This research focuses on addressing this issue by developing an optimal signal design strategy specifically for HLLD traffic conditions which can enhance the performance of traffic signals in developing countries.
Towards this end, this research first develops a queueing theory based theoretical delay model that explicitly incorporates HLLD traffic conditions' characteristic features like lack of lane discipline, violation of the First-In-First-Out rule, and a large mix of vehicle types. The developed model shows a 64% lesser error in average control delay estimation than the in-practice delay estimation models under HLLD traffic conditions. The developed model is then used for signal optimisation under HLLD traffic conditions, and reductions of up to 24% in control delay compared to the in-practice signal timing approach are observed. Further, the research also proposes a real-time delay-based signal timing strategy, which, when used in combination with the optimal time of the day plan based on the delay model for HLLD traffic, yields up to 33% reduction in average intersection control delay compared to in-practice signal timing approach.