Major traffic incidents result in a substantial induced-delay, waste of fuel and extra toxic emissions. Although many past studies have evaluated the effectiveness of various incident management strategies to mitigate these impacts, the knowledge regarding the significant factors that affect the effectiveness and efficiency of multi¬-agency and multi-jurisdictional incident management programs as well as the impact costs of major traffic incidents are still limited. This has made it difficult to select the most cost-effective and highest impact countermeasures for future investment.
To address and improve the knowledge in this area, this thesis developed an integrated evaluation framework that can be used to examine various incident management countermeasures, and justify efforts in pursuing and securing the funding necessary for the improvements of traffic incident management in the future. The specific objectives of this research were: (1) to identify and examine incident management factors that affect the effectiveness and efficiency of traffic incident management and then undertake an evaluation of high impact countermeasures; (2) to determine major incident duration contributing factors in the Australian context and hence develop a rapid incident response priority model; (3) to evaluate incident-induced delay estimation models (empirical, macro-simulation and micro-simulation); (4) to quantify the impacts of major traffic incidents and estimate the associated costs; and (5) to evaluate cost effective incident management countermeasures aimed at reducing the impacts of major incidents.
To achieve these objectives, several approaches were employed in this study. Firstly, a comprehensive literature review was undertaken which provided guidance on appropriate knowledge gaps. Secondly, a preliminary study was undertaken using both expert interviews and a questionnaire to gather initial evidence and providing a solid basis to progress to the next stage. Thirdly, a Delphi technique was used to examine incident management barriers and potential countermeasures, by collecting expert opinions, conducting content analysis of major incident debriefing reports, focus group discussions, and undertaking in-depth practitioner interviews. Fourthly, past incident records were analysed using logistic regression to determine major incident indicators for better incident response prioritisation. Then, an evaluation of available and potential modelling tools (empirical - static and stochastic, macro-simulation and micro-simulation) was undertaken to estimate traffic incident-induced delay with a consideration of low to high traffic volumes, availability of diversion, traffic recovery time, and incident clearance time. The results were then used to select an appropriate modelling tool to estimate the impacts of a major incident. Finally, a hypothetical case study was undertaken in Brisbane, Australia using a micro-simulation approach to estimate the network area-wide impacts of a major traffic incident and associated costs; and to evaluate the incident impact reduction of incident management countermeasures.
Summary of the thesis significant findings:
• Various incident response prioritisation criteria have been used by the road and traffic agency and the police agency that could result in providing ineffective responses
• Inability to effectively classify incidents and assign proper response priorities have caused difficulties for the responding agencies to provide appropriate response (human and equipment)
• The current level of understanding among key incident responders on the factors that affect the duration of major incidents is quite limited.
• The three most critical incident management countermeasures with higher impacts were an improved support technology for detection, verification and communication; deployment of a fully integrated incident decision support tool; and an improved on scene incident coordination;
• Fatal crash, heavy vehicle crash, heavy traffic flow, traffic flow disruption, travelling lanes fully blocked, HAZMAT spill, number of people injured, and medical attention required are significant variables in predicting major incident priority;
• A proposed ‘assessment checklist’ for traffic incident response prioritisation was developed to assist traffic operators at the traffic management centre (TMC) to effectively assign incident response priority and hence quickly deploy appropriate human and equipment resources to the incident scenes.
• By applying a 65% capacity reduction assumption in the micro-simulation model, 36% more incident-induced delay was estimated as compared with 50% capacity reduction assumption for a two hour incident clearance duration that blocked one lane of a two-lane motorway; and
• An incident which caused a full blockage incurred 40 times more associated impact costs as compared with a major incident which caused a partial lane blockage. A 23% cost saving can be achieved by clearing one lane of a fully blocked two hour major traffic incident after 90 minutes, while a 37% cost saving can be achieved by clearing all blockages after 90 minutes.
Finally, an integrated evaluation framework above can be used to evaluate traffic incident management potential countermeasures and hence provide reliable outputs to justify efforts in pursuing and securing the funding necessary for the improvements and advancements of traffic incident management in the future.