Assessing The Speed Flow Characteristics And Road User Cost Of Smart Motorway Using HDM-4

The rapid growth of national motorization has led to more and more vehicles on motorways, which in turn increases congestion. Conventional solutions such as building more roads and widening cannot meet the huge traffic demand, active traffic management is an imperative way to mitigate traffic congestion.Active Traffic Management (ATM) including Variable Speed Limit (VSL) and Hard Shoulder Running (HSR) is often used to improve traffic condition on motorways, a motorway which all or part of it using ATM is called Smart motorway. Different from the traditional fixed speed limit, VSL allows the speed limit to vary with different traffic flow, which can reduce the speed differences between vehicles and improve the overall traffic condition. HSR allows vehicles running on the improved hardshoulder at peak times in order to provide additional traffic capacity and improve road service level. VSL and HSR are the foundation of others ATM measures.This study aims at investigating the speed-flow characteristics, user benefit of smart motorway and developing an assessment framework to evaluate road user benefits using HDM-4.Highway Development and Management system series (HDM-4) is developed by Word Bank which has been used for over two decades to combine technical and economical appraisals of road projects to prepare road investment programmes and road network strategies analysis by considering internal and external effects. This project is using its road user estimation function to estimate the road user costs of M42 under different operation regimes.A case study is developed based on traffic data collected from M42 Junction 3a-7 smart motorway, three cases are developed:Non-VSL period, VSL period and HSR period based on data collection from UK official TRADS and JTDB database, by analyzing the traffic data under each case, the traffic flow characteristic, average travel time and travel time reliability can be evaluated. Based on that the road network is modelled and calibrated in HDM-4 and real traffic data of three cases is input, then road user road of Non-VSL, VSL and HSR can be estimated. The HDM-4 results of Non-VSL, VSL and HSR are then compared and discussed to investigate the road user cost saving. In the discussion chapter, the benefits generated from HDM-4 are then compared with published benefit to examine the consistency of analysis. The choice between VSL and HSR is also discussed, the limitation of HDM-4 in this study is concluded in the end.The result shows that VSL is effective in improving the overall traffic condition to provide smooth, less collision traffic, it can be activated anytime based on the traffic flow, weather condition and incidents, however it cannot solve the congestion problem radically. Compared with VSL, HSR is activated when traffic flow is very high and congestion starts to happen, HSR can increase the capacity of the motorways and reduce severe congestion, when traffic is not high, the VSL works to manage the traffic.This study provides an innovative way to get accessed to road user benefit of smart motorway. Compared with the traditional empirical studies, the combination of HDM-4 analysis and data analysis makes the result more convincible and can be useful to road agencies to introduce appropriate smart motorway schemes.