Use of analytic hierarchy process (AHP) for solving traffic issues due to ad-hoc urban planning

Abstract

In Sri Lanka traffic issues are becoming progressively worse due to ad-hoc urban planning. Delays, environmental pollution, higher depletion of petroleum, and increase in stress level of road users are some direct impacts from traffic congestion. To identify the causes for traffic congestion and to seek for possible solutions, Galaha Junction to Gatabe Roundabout in Kandy – Colombo road (AA 001) was selected as the case study area. The data was collected using series of traffic surveys (vehicle volume counts, pedestrian counts, delay survey, etc) and analyzed to exemplify the gravity of the traffic congestion due to ad–hoc road side developments. The shockwave analyze was performed to find the delay time and queue lengths. It is found that, the existing capacity of the road is not enough to carry the current traffic load, and pedestrian must separate from the vehicle according to the AUSTROADS classification. To minimize the problem, alternative traffic solutions are proposed for both vehicle flows (e.g., flyover, road widening and tunnel) and pedestrian flows (e.g., overpass and underpass). Next a set of criteria are defined to evaluate the best solution. Cost of each solution, environmental impact from the solution, land acquisition requirement for each solution, construction time and the demand (time taken to get down the Level of Service (LOS C to LOS D)) were selected as the criteria. Environmental impact is taken as a qualitative criterion while others are taken as the quantitative criteria. Analytic Hierarchy Process (AHP), a commonly used multi criteria decision support system, is used to obtained best alternatives for smooth vehicular flow and safe pedestrian crossing separately. Later tree diagram concept was used to reach the best composite solution for the problem. The fly over for vehicles and the underpass for pedestrians are the best solution from AHP.