Rising traffic congestion in urban areas has resulted in an increased focus on the economic, financial and travel reliability impacts. Understanding traffic incident causation and then an increased emphasis on prevention, has the potential to significantly reduce the number and impact of traffic incidents.
It is instructive to look at the extensive research in the causes of crashes and the development of a body of knowledge on traffic safety countermeasures and injury prevention. There is little published research into causes of traffic incidents.
Anecdotally causes of traffic incidents include such things as inattention, careless or reckless driving behaviour, excessive speed, poor judgement, impairment (alcohol, fatigue, drugs etc), distraction, poor loading of goods vehicles, insufficient fuel, unroadworthy vehicles, road works and adverse weather.
The modern scientific approach to traffic safety really began with Dr William Haddon, who in the late 1960’s developed the first systematic method of identifying a complete range of options for reducing traffic crash impacts.
The Haddonmatrix (see example in Table 1) applies basic principlesof public health to the problem of traffic safety and is an effective tool for revealing where and when to best conduct traffic safety interventions to reduce the potential for an crash to occur and reduce the severity of those that do occur.
Adapting Haddon’s Matrix for incident prevention, focusing on the ‘before event’ phase, potential incident risks can be assessed, as in the example in Table 2, after analysis of data of incident history.
The three main approaches to prevent road crashes (the three E’s) of engineering (measures focused on infrastructure) enforcement and education can also be applied to incident prevention. Countermeasures can then be developed to address the identified causes and potential risks.
Education: for road safety this means driver training and includes various education or information campaigns. For incident prevention, education could also be extended to provision of real-time information of traffic conditions etc, plus advice on driving safer and avoiding incidents.
Enforcement: obviously applies to action to enforce the road rules to minimise high-risk driver behaviour. In many cases traffic incidents are also caused by inappropriate driver behaviour, such as speeding, so a perception that a roadway is being managed, by an appropriate level of enforcement, will improve safety, and also reduce incidents. Intelligent transport systems, such as automated camera enforced variable speed limits can manage the speed of traffic, improve traffic flows, and reduce crashes and incidents.
Regulations, penalties and enforcement can also be used to ensure vehicle roadworthiness, improve load stability and reduce the potential for vehicles running out of fuel at critical locations.
Engineering: High-risk locations or ‘blackspot’ is an approach to tackle unsafe situations at locations with the most crashes. A similar approach could be taken for traffic incidents, identifying high-risk locations through data analysis.
Incident prevention principles include providing a consistent and predictable road environment, in terms of functionality of the road and speed profile.
Narrow shoulders and structures, and tunnels provide hazardous situations and increase the potential for incidents or when an incident does occur increases the likely impact. Providing wider shoulders and rumble strips at the edge of the lane are measure that can be used in high-risk locations.
Road works often introduce additional hazards and risks, such as narrower lanes, lower standard geometry, lower quality surface conditions and distractions. Enforcing appropriate driver behaviour, including lower speed limits and ensuring good delineation of the path through construction zones are key measures to reduce incidents.
Traffic incident prevention countermeasures have considerable potential in reducing the impact of incident induced congestion on major traffic routes.
Table 1: Haddon’s Matrix: Crash Analysis of Traffic Safety Risks
Table 2: Analysis of Incident Causes/Risks