An Analysis of the Performance of Low Capacity Diversion Routes during Motorway Incidents

Abstract

The effective operation of any transport infrastructure component is essential in maintaining and developing the growth of communities, towns and cities. In particular peak traffic times it may be hard for the transport agency to keep the network operating in an optimal state, as there may be many conflicting priorities. When an incident happens on the road network, Incident Management procedures and plans play a major role in helping the network work through the impacts of the incident to achieve pre-incident traffic conditions. There are many objectives with these incident management programs including reducing costs, delays and emissions while trying to provide benefits to the wider community. Part of the incident management plan may include the use of a diversion route where incident-induced traffic queues are directed from the incident bound motorway, around the incident site, to later re-join the motorway. The ability of this diversion route to cope with this extra traffic can be measured qualitatively and quantitatively by examining level of service and capacity criterion respectively. The rate of diversion from the motorway plays a major part in determining the optimal operating conditions for a diversion route, particularly if the diversion route has a small capacity. Unfortunately, low capacity usually plays hand in hand with low level of service and as such, the achievement of a fine working diversion route during motorway incidents is paramount. With the addition of another diversion route, the management of incident-induced traffic queues could be seen as a little easier, but this may not be totally true. The present research aims to address these difficulties which are faced by road and transport operating authorities. This is achieved primarily by the use of a traffic microsimulator (AIMSUN) which can be used to model different incident scenarios to give an indication of how to effectively use a diversion route network with the aim to restore pre-incident traffic conditions. These outcomes can then be utilised by Traffic Management Centres in their incident management procedures and be further used (with some modifications if necessary) to other areas of motorways in this local area and other parts of the state.