Evaluation of emission level increment in urban and sub urban highway work zones

Abstract

A highway work zone is where a rehabilitation of an existing highway is being carried out. It can result in reduced flow, reduced capacity, and average speed. Also there is a high risk of safety involved in every work zone. Highway work zones are of particular importance when it comes to efficient travel operations of a road network, especially in areas where there is high traffic flow, such as urban areas. Impact of work zones related to emission and air quality monitoring is often overlooked in such projects. Impact of a work zone for emission is higher in a developing country due to the nature of vehicle fleet. In this study, in order to evaluate the impact of work zones in emission in urban highway work zones and major arterial roads in Sri Lanka, emission modelling was done for a major arterial road in Sri Lanka, using HDM-4 (2008) software for five main vehicle types. Analysis included two road sections, one where rehabilitation is carried out and one where the road is operating under normal flow conditions, for emission levels during peak and off peak, for each vehicle type, and various volumes. It was shown that emission levels significantly vary with vehicle type and volume, which suggests that vehicle composition and road traffic volumes are significant factors when considering the impact of a work zone. Also roughness variation has resulted in 50-70% increase on emissions over a normal section. Further, increase of motor bikes and three wheels has resulted in 8-12% in emission increase on the same type of road based on the roadway classification. These findings can be used to set up a minimum standard in work zone maintenance which could result in millions of cost savings to the economy.