ISA systems' effects on road safety and climate change – study based on FOT data

Creation date: 03 April 2009

Data from field trials with a fleet of 20 cars equipped with a voluntary (overridable) ISA system formed the main input to a study of University of Leeds about ISA systems’ effects on road safety and climate change. The main objectives of the study were to investigate the potential reduction in CO2 emissions, to estimate the impact on the number of people killed or injured in road accidents, to perform a cost-benefit analysis and to investigate drivers’ and fleet managers’ attitude towards ISA systems.

Main findings include: 

• the environmental benefits of ISA are real but low: ISA has a positive impact on CO2 on motorways (speed limit 70 mph/ 113 kmh); for roads with speed limits lower than 70 mph ISA has no impact on CO2 emissions
• voluntary or mandatory ISA can have a large effect on the future accidents number and particularly on the more severe crashes
• the implementation of ISA is clearly justified from a social cost and benefit perspective; social benefits of the accident savings far outweigh the values of CO2 savings
• to increase usage of ISA legal fitment requirements are most effective; financial incentives would only outreach to part of the drivers and there is the potential for incentive to be wasted on those who do not need them because they are convinced of the safety benefits anyway

The full report on ‘Speed Limit Adherence and its Effect on Road Safety and Climate Change’ published by University of Leeds can be downloaded here.

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