|Summary results of impact of ISA systems on CO2 emissions. Click to enlarge.
The UK government’s Commission for Integrated Transport (CfIT) and the Motorists’ Forum (MF) recently issued a joint report evaluating the impact of implementing an Intelligent Speed Adaptation (ISA) system across the entire road network on reducing deaths and injuries on the UK roads and on reducing fuel consumption and emissions of CO2 and criteria pollutants. They partners commissioned the Institute for Transport Studies, University of Leeds to produce the report.
ISA systems use enhanced navigation systems which incorporate speed limit as a road attribute to compare the local speed limit to the vehicle speed. The ISA system automatically detects the road on which a vehicle is travelling—and hence the speed limit—without any user intervention. ISA systems take three basic forms:
Advisory ISA, which advises the driver when the vehicle is exceeding the speed limit with an audible and/or visual warning;
Overridable (or Voluntary) ISA, which controls maximum speed based on location but allows the driver to override the speed limiting function and regain full manual control until a new speed limit is encountered and/or the road speed drops beneath the current speed limit at which time ISA regains control; and
Mandatory ISA, which uses a speed limiting function that the driver cannot override to control maximum speed.
Research on ISA in the UK has been going on for more than 10 years, including a major ISA-UK project funded by the UK’s Department for Transport (DfT) between 2001 and 2006. The new report builds on and extends this previous work, including the final report on the ISA-UK project published by DfT in September 2008.
Of the two proposed benefits of ISA—GHG emissions reduction and increased road safety—the Leeds researchers concluded that the calculated social benefits of the accident savings far outweigh the values of fuel or CO2 saved. Among the findings presented in the report:
Overall, changes in CO2 emissions are not very significant on roads with a speed limit of 60 mph or lower. But on 70 mph roads, there is potential for a substantial reduction in CO2 emissions of 5.8% (+/- 0.7%) with a mandatory ISA system.
On the modeled rural network, neither overridable nor mandatory ISA make a major impact on overall CO2 emissions or fuel consumption rates at any level of penetration.
In the two modeled urban networks, increasing ISA penetration had a small detrimental effect on both CO2 emissions and fuel consumption, increasing both by up to 3%. The detrimental effect is stronger at levels of ISA penetration above 20%. This is because cars tend to operate most efficiently at speeds above 30 mph. On the other hand, the more elaborate emissions modelling of the speed profiles from the UK trials indicated small savings in CO2 emissions and fuel consumption on both 30 and 40 mph roads, most likely because of reduced acceleration.
No substantial effects were found regarding other pollutants.
The implementation of ISA systems is likely to make a negligible contribution to reducing overall broadband noise levels.
Universal usage of mandatory ISA could eliminate nearly 29% of injury accidents.
The potential for reducing accidents is greatest on 30 mph roads where there is considerable propensity to exceed the speed limit and crashes involve collisions with pedestrians and cyclists
Advisory ISA is predicted to be substantially less effective than the intervention based (overridable and mandatory) forms of ISA.
In less than 15 years, under virtually every scenario, ISA recovers its implementation costs. Over the period 2010 - 2070, the benefit to cost ratios are very large, apart from the Advisory only ISA scenario, which is not considered a realistic option because it can be assumed that some parts of the market will choose to adopt overridable ISA.
Attitudinal work found that the public is segmented into three major groups: those who are extremely hostile to ISA and who declare that no amount of incentive would sway them to purchase or use ISA; those who are non-committed and could be persuaded by incentives; and those who conclude their is a safety potential in ISA and do not require incentives to adopt it. “Thus there is the potential for incentive to be wasted on those who do not need them, and a danger that, if adopted, there would be a considerable minority of refusers.”
The study has predicted substantial benefits from the introduction of ISA. These benefits consist principally of the savings in accidents and in particular in more severe accidents. The savings are substantial under all the scenarios examined, and strategies that promote higher penetration of ISA and earlier adoption of intervening forms of ISA lead to greater impact. Thus ISA can be considered as a system with major safety potential.
The environmental benefits of ISA are real but less considerable. They consist in the main of reductions in fuel consumption and in consequent CO2 emissions.
...Interestingly, there was significant support in the focus groups for the government moving ahead not only with requiring fitment but also in the longer run with requiring usage. The analogy was drawn with the history of seatbelt wearing. Even among the strong opponents of ISA, there were statements that it they were required to use it, they would comply.—Speed limit adherence and its effect on road safety and climate change
Speed limit adherence and its effect on road safety and climate change (University of Leeds, 2008)
Intelligent Speed Adaptation (UK Department for Transport, 2008)