10 by 10 - a 55mph national speed limit

The following is written by Daniel Scharf of Green Speed  (www.greenspeed.nildram.co.uk)

As there is no reason why the transport sector should expect there to be easier savings in carbon in other sectors the Government should be required to assess policies that are reasonably necessary to achieve savings in accordance with law and aspirations (80% to 90% by 2050).

A properly enforced speed limit of 55mph will have an immediate effect of saving over 2MtC.  The VIBAT study carried out for the DfT by UCL and Halcrow recommended that the only way in which the Government could achieve its carbon reduction targets (60% by 2030) would be to have a 50mph speed limit.  There are no scenarios for any of the years for which targets have been fixed that demonstrate that the required reduction is possible without lowering and enforcing the national speed limit.  It is also fundamental that this measure is immediately available and low or no cost and this cannot be said of any other transport measure.  Even the possible cost of slower journeys might not arise because of less congestion and shorter planned journeys.  Drivers will save fuel and cause less wear and tear on tyre and vehicles.  Although less petrol/diesel will be sold, the higher prices that reflect its value as a depleting non-renewable resource, will maintain tax revenues.

The advantage of saving of carbon emissions in the short term cannot be over-estimated, as long term savings will be less effective and are largely dependent on technical advances or more draconian regulation.  A regulation affecting only those driving over-weight and over-powered vehicles too far and too fast should be politically attractive.

Lower car speeds improve  the comparative advantage of bus, coach and train, without the need for the substantial investment in high speed rail.  The modal shift to relatively faster public transport also puts more paying bums on seats without fare reductions.  A 55mph national limit will be supportive of a 20mph limit in built-up areas due to vehicles engineered and drivers attuned to slower speeds. Slower buses in urban areas will make walking and cycling safer and more attractive.  A vehicle technology designed for a maximum of 55mph is essential to prevent an increase of carbon from driving conventional cars at 20mph.

The VIBAT study did not take into account of the knock-on effects of lower speeds.  To some extent these are matters for speculation but, most if not all effects/synergies would appear to increase the carbon reductions from transport.  A consistent package of policies, or just a trigger policy with encouragement of the knock on effects is the only approach that will result in the necessary carbon reductions.  To the immediate 2.5MtC saving, will be a change over ten years of most of the car fleet from and average of about 150g/km to 110g/km. With a smaller fleet this would still amount to over 33% reduction.  The inelasticity of journey times (<1hr per day commuting) is likely to reduce car journey lengths over a period while homes and jobs change.  A reduction from 70+mph to 55mph  is about 20% for those continuing to use the car.  As the speed of trains will be maintained and the speed and reliability of coaches and buses will increase there will be fewer car users.

Lower speed would make alternative fuels more attractive but until low carbon electricity is more generally available this is not a selling point for lower speeds.

The main imponderable is the effect of reduced congestion as this might make car use more attractive, but the reduction of stop/start driving and the free flow of vehicles in urban areas at 20mph by increasing road and junction capacity is likely to be more significant.

The savings of life and limb and associated costs and trauma should not be forgotten.  Lower speeds might incidentally make land in urban areas available for housing where previously the access had been adjudged to be dangerous.

The next iteration of the virtuous circle will include the benefits of  the car losing its psychological pulling power. This will be seen in the spread of car clubs and green travel plans for work and leisure destinations.  Web cams and Skype will increase telecommuting.  Travel is not a necessity like shelter and food so is likely to reduce if there should be a national or international lowering of the standard (in a material sense) of living.

Slow speed technology is eminently transferable (just as the Mercedes culture has been in developing countires) and the systemic changes associated with lower speeds and carbon savings would inevitably follow.