Slower Speeds Initiative research shows speed reduction the single most effective measure to cut carbon emissions from road transport now.

Joint research undertaken by the Slower Speeds Initiative and the UK Energy Research Centre shows that a lower top speed limit would be the most ‘significant, certain, immediate, equitable and cost-effective’ way to reduce carbon emissions from road transport.

Reduce C02 emissions by 1.9MtC a year
Enforcing the 70mph limit would reduce emissions by nearly 1 million tonnes of carbon (MtC) a year. A new 60mph limit, properly enforced, would reduce annual emissions by an average 1.88MtC.

The savings are equivalent to between 15% and 30% of those expected by 2010 from the transport sector according to the UK Climate Change Programme (UKCCP). Unlike the other transport measures in the UKCCP, lower speed limits could be introduced almost immediately and have the advantage of being certain and requiring no technological innovation.

Equitable and potentially popular when compared to other measures
The authors of the report, ‘Getting the genie back in the bottle’ (148kb pdf), also argue that as well as being more equitable than other measures, lower speed limits would be more popular, if properly explained. Drivers would benefit directly from lower running costs and safer roads. In addition lower speed limits would entail less behavioural change than other soft measures.

Wider benefits and far-reaching effects on travel demand and vehicle design
Lower top speeds would lock in fuel efficiency improvements that have so far been used to lower the costs of travelling further, faster, in heavier cars. In the longer term a lower top speed limit would help to curb traffic growth, the most intractable problem in getting carbon emissions from surface transport under control.

Initial indications are that controlling top speed would be one of the cheapest carbon reduction policies across all sectors, especially when wider benefits, such as casualty reduction and congestion reduction are taken into account.

A 60mph limit was taken for purposes of illustration. The report proposes a more comprehensive appraisal to establish whether even lower limits would be of greater benefit and to provide the basis for informed public debate.

The report concludes:

‘The need to meet CO2 reduction targets and protect society from the economic effects of energy shocks is increasingly urgent. A policy of current speed limit enforcement and, better still, lowering the speed limits, would bring significant, certain, immediate, equitable and highly cost-effective reductions in carbon emissions. What is more this policy instrument has the potential to slow traffic growth and influence the vehicle market with further carbon reduction benefits, in addition optimising current road network capacity and leading to signficant road safety benefits. Overall, it would help to create the conditions for the transition to a more sustainable transport system.’

The report was a winning entry to the Low Carbon Vehicle Partnership’s ‘Low Carbon Road Transport Challenge’. The conference brochure (1MB pdf) containing all eight winning entries can be downloaded from the LowCVP website.