Large urban areas are facing an increasing challenge of mobility (congestion), safety and environmental impacts due to traffic incidents.
Traffic incidents are estimated to account for about 25% of traffic congestion and bad weather another 15% (FHWA 2007). Hence congestion due to traffic incidents and bad weather can be as much as 40% of the total congestion.
Traffic incidents can have significant impacts on road users and the community. Injured people need to be recovered quickly from crashes and the potential for secondary incidents needs to be avoided. The safety or emergency responders and traffic controllers are at risk in moving traffic conditions.
Traffic delays result in lost time, schedule disruptions for public transport, financial costs for freight operators and local businesses and increases in vehicle emissions due to idling traffic.
While people can factor in “normal” congestion as part of their commute, unexpected congestion can make people late for work, meetings, appointments, or other activities.
Alternatively, people may choose to leave early in case they run into unexpected traffic, meaning they also may arrive earlier than necessary. A reduction of one minute of travel time under unexpectedly congested conditions is valued at over 2.5 times the value of one minute of time under normal condition (Small et al 1999).
Typical Impacts of Traffic Incidents
- Regional Impacts: Diminished cost competitiveness and market growth opportunities lead to a reduced ability to retain, grow, and attract business. Increased emissions and energy use.
- Freight Impacts: Longer travel times and less reliable delivery times. To compensate typically add vehicles and drivers and extend their hours of operation, eventually passing the extra costs along to consumers.
- Business Impacts: Increased cost of delivering goods and services, costs of spoilage for time-sensitive, perishable deliveries and maintaining greater inventory to cover the undependability of deliveries.
- Household Impacts: As travel time and vehicle operating costs increase and reliability and mobility decrease, then the quality of life is diminished.
- Agency Impacts: Additional cost of responders, equipment and materials – overtime, equipment hire, clean up etc (opportunity cost). Increased exposure to occupational health and safety hazards from passing traffic, hazardous materials, etc
- Road User Impacts: Exposure to secondary incidents from end of queue (high speed differentials), distraction (especially at speed), etc
Quick clearance of traffic incidents can greatly assist in the reduction of traffic congestion through minimising traffic delays, reducing the number of secondary crashes that occur and decreasing vehicle emissions.
FHWA (2007) Traffic Congestion and Reliability: Trends and Advanced Strategies for Congestion Mitigation Strategy to Reduce Congestion, Federal Highways Administration, Washington DC.
Small K, Noland R, Chu X and Lewis D (1999) Valuation of Travel Time Savings and Predictability in Congested Conditions for Highway User-Cost Estimation, National Cooperative Highway Research Program Report 431, Transportation Research Board, Washington.