Effectiveness of Incident Management on Network Reliability – Stage 2

Following on from earlier LTNZ research on incident management and network reliability, this research for NZTA (while Glen Koorey was working at Canterbury University) investigated how ITS (Intelligent Transport Systems) measures, such as adaptive signal control (e.g. SCATS) and Variable Message Signing (VMS), could be used to improve the transport network efficiency during traffic incidents. Following a literature review, a motorway and arterial road traffic network was modelled to determine the most appropriate traffic management strategies (in terms of overall network reliability) to apply when such incidents are detected.

For a motorway blockage scenario, the chosen mitigation (implementing VMS and allowing use of the motorway hard shoulder) was estimated to produce a 20% reduction in average trip times, although on some selected diversion routes the estimated effect was less than 7%. The reduction in the standard deviation of trip times was much larger (~80%). For an arterial road lane closure, the chosen mitigation (revising the SCATS management plan) was estimated to produce quite small improvements in average travel times (<2%). The estimated effect on various diversion routes varied considerably up and down.

For a large complex network, it may be necessary to have a large number of incident management plans, to cover the range of incident scenarios that might occur. A ‘template’ process is proposed for identifying the most significant risks to a network, comparing the treatment options, and developing suitable contingency management plans.