Reducing the national speed limit (from an unenforced 70mph to an enforced 60mph or below see Netherlands 2019) would be a sensitive and pivotal intervention, leading to rapid, profound and an over-sized systemic response.
A lower speed limit triggers self-reinforcing feedbacks within the transport with little rebound (due to the constant time travel budget the cost savings from more efficient driving is not spent on extra miles). The Environmental Audit Committee Reducing Carbon Emissions from Transport 2005/6 heard evidence from Bannister and Hickman (the VIBAT study 2005) that a lower national speed limit was necessary to achieve a 60 carbon reduction by 2030. The committee accepted the recommendation, adding that such a measure would show that the Government was serious about climate change. David McKay pointed out that this change be achieved through a twiddle of a switch. It would be equitable, could be done tomorrow, and at no public expense. The objection from the Treasury due to the loss of tax revenue resulting from efficient driving has been removed through the support for the power-shift to electric vehicles, that would also be rolled out faster as the optimum speed for a car is about 50 mph, maximising the range of the EV, and removing the competitive advantage of the internal combustion engine (currently poisoning urban areas at lower speeds).
The greater the speed differential between vehicles, the greater the risk of accidents. Most HGVs are speed limited to between 50 mph and 60 mph. PSVs are limited to 60mph. Highway safety would be greatly improved if car speeds were similarly limited. Lower car speeds would stimulate a modal shift to bus and rail, and safer roads would encourage cycling. Overall this would result in lower costs to the NHS, with fewer and less severe injuries, and more active travel.





Trigger (intervention)




Feedback Dynamics


Timescale and scaleability





Daniel Scharf

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