The Climate Emergency – 20mph Reduces Emissions, helps traffic reduction and reduces oil dependency.

By Anna Semlyen, Cutting Your Car Use author, National Campaign Manager of 20’s Plenty for Us

Climate activists are ramping up direct action because scientists say we are running out of time for politicians to act before the 1.5-2 degree warming that is irreversible.  Top personal ways to decarbonise and prevent climate chaos are to stop eating meat and to stop flying.  20mph limits enter the climate debate as crucial to reduce fossil fuel use for transport in towns and villages. Politicians must act to make it more possible for citizens to ‘do their bit’ to get about the places they live in greener ways.

Local Councillors set road speeds locally and MPs at National Level. 20’s Plenty encourage everyone to lobby them for 20mph limits without humps. Slower speeds offer three major benefits for the climate.

  • Less fuel is used
  • People feel more confident at active travel
  • Reduce oil dependence

Emissions - The Institute for Welsh Affairs (IWA) recommend a national default 20mph limit in its Decarbonising Wales report[1].  IWA cite a 12% reduction in gear changes, 14% in braking, 12% in fuel use and transport emissions in residential areas. 20mph emissions are reduced due to less acceleration between braking in urban stop/go driving. Getting a vehicle to 30mph takes 2.25 times more fuel (than to 20mph[2]). Toxic diesel emissions are very much lower.  20mph limits is equivalent to taking half the petrol cars off the roads[3].

Safer - 20mph limits raise actual and perceived safety - crucial in a driver’s decision on how to get around. 20mph is therefore an effective traffic reduction policy if applied door to door. 

Behaviour change research on traffic reduction centres on altering perceptions of the relative safety/health benefits, convenience and cost in comparisons of the car and non-car options.  Active travel (walking, cycling, public transport) is always healthier than driving (provided you’re not hurt in a crash or molested). 

Drivers first weigh up safety risk in their decision of how to go.  Indeed it also enters the decision on the weight when buying their own car and its safety features – leading to increasingly heavily armoured cars where heavier equals higher fuel consumption and danger for others outside in a negative spiral.

The UK’s transport sector is the most polluting[4]. The speed and volume (quantity) of motor traffic affects perceptions of personal safety and willingness to walk, cycle or take public transport.  Reducing speeds is crucial to reducing traffic volumes. Edinburgh’s 20mph trial found walking trips rose 7%, cycling trips rose 5% and car trips fell 3%[5].

Risk – Driver perceptions of safety must be not only be changed, but radically step-changed to successfully entice drivers out of cars.  Behaviour change marketing also aims to nudge parents and carers to actively encourage (or at least permit), vulnerable family members (children, the disabled and elderly) to get around car-free.  20mph works. Those considering cycling to be unsafe fell from 26% to 18% in Edinburgh[6]. The IWA say say 20mph is associated with decreases in injuries, crashes, including pedestrian and child pedestrian injuries of 17 - 70%.  20’s Plenty for Us cite studies where at least a fifth of casualties were prevented by wide 20mph limits[7].

Like you can’t diet without restricting calorie intake, society can’t expect people to drive less without making non-car alternatives safer.

Convenience – 20mph also makes not driving seem more attractive as it could feel as if there isn’t such a time advantage to driving. In reality total time taken isn’t significantly affected. Yet it is the perception that driving at 20mph doesn’t give a big time advantage which brings traffic reduction.

Cost 20mph is cheaper per mile reduced than almost any other traffic reduction method – (except road closures or not road building).  It is also popular with over 70% of people in Dept for Transport research[8]. 20mph reduces risk very effectively of all travel options, long term, for a once off cost of around £3 p/head.

Environmental groups wanting wide 20mph limits include: Friends of the Earth; CPRE; Campaign for Better Transport; The Conservation Volunteers; Environmental Protection UK; Chartered Institute of Environmental Health; CTC the national cyclists’ organisation; Environmental Association for Universities and Colleges; Ramblers’ Association; Sustainable Development Commission; ETA Trust; Transform Scotland; Sustrans; Living Streets; Lib Dem & Green Parties; Stockholm Environment Institute and more.

Friends of the Earth say, in urban areas, around a third of carbon emissions from driving could be avoided if people were able to switch to walking and cycling[9].

Extinction Rebellion is gaining traction to the climate emergency as people wake up to fact that we must do more to protect our planet and its vital life-support system. 20mph helps us to burn less fossil fuels and gets more people to walk, cycle or use public transport.  It a major part of the solution to get drivers out of cars and away from fossil fuel dependence and the negatives to the climate and wars for resources that a dependence on oil entails.

Contact your elected representatives to lobby them to make 20mph limits the  normal road speed where you live today.  Ask [email protected] @AnnaSemlyen1 07572 120439 for help.











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  • Rod King
    commented 2020-01-17 15:52:52 +0000
    Hi Christine. We don’t advocate speed bumps. It seems rather a course way to communicate with drivers. We prefer “hearts and minds” rather than “buttocks and spines”. But the load on suspensions from speed bumps is actually proportional to the speed someone drives over them. So maybe just driving over them at their design speed is preferable to testing out the suspension unnecessarily.
  • Christine Jones
    commented 2020-01-17 13:49:52 +0000
    I don’t mind 20 mph limits, but speed bumps ruin your car’s suspension.