Costs of Separated Cycle Infrastructure Are Mostly Due to Allowing 30mph Driving – 20mph is Plenty

20’s Plenty for Us campaign for community-wide 20mph limits and separated, high quality infrastructure where higher vehicle speeds are justified. Infrastructure costs are due to letting drivers travel at speeds where interactions between cyclist and motor vehicles are unsafe.  The cost of infrastructure is largely the cost of driving at speed and are not costs of cycling and walking.

Politicians and professionals realise utility cycling (i.e. to work, shops, school) reaps massive benefits - easing congestion, traffic reduction, school run issues, relieving parking problems, improved air quality, raised public health, physical activity levels and more.  Yet the British Social Attitudes Survey finds only 5% of people cycle at least weekly. What’s the most cost effective way to make a step change to increase utility cycling?  Good evidence from places with wide 20mph limits confirms that lowering speed limits gives most returns per pound spent.

Traffic speed and volumes inversely relate to walking and cycling levels. The World Health Organisation say 20mph is the maximum safe speed where there might be conflicts between cars and cyclists.  Safety fears are what people say most puts them off cycling. Cycling casualty rates fall 20-40% with wide area 20mph limits.

Making side streets 20mph has raised cycling levels. Cycling to school trebled in the Edinburgh 20mph South Central trial[1].  A key to maximizing utility cycling gains is to set 20mph limits or separated infrastructure along desire line routes, i.e the direct routes.  Space is most easily found for off-road cycling on quiet routes - eg old railways or river paths. Yet, the next tranche of those who might be willing to cycle more may not find indirect paths enticing due to being in a hurry and wanting to minimise journey time. 

For traffic engineers the key to fitting in separated cycle infrastructure is finding available land alongside highways or enough carriageway for lanes of a least 1.5m wide (2m is recommended).  Yet, what if there isn’t space for a joined up safe separated cycle network? The choice becomes introduce 20mph limits or reduce parking or driving lanes (ie reduce motor vehicle road space). Separated lanes for cyclists and 20mph limits both have their place.

Wide 20mph limits are popular, easy to do, quick and cheap to install once there is political will. They are also great value for money with minimal signage requirements costing only about £1.50 per head of population[2].  Many funding streams can be used and wide area 20mph will always beat small scale schemes in cost effectiveness as they benefit the many[3]. For a city of 200,000 people 20mph limits is only £300k. We recommend that authorities use public health experts for driver education, engagement and gain police agreement to at least minimal enforcement, with an optimal spend of  £2-3 per head.

Residential 20mph limits without humps have 70% approval. Popularity rises once installed. 20mph limits raise cycle rates for a minimal cost per additional trip.  Note that the costs of cycle infrastructure are not due to cycling and walking, but come from allowing faster than 20mph driving. If drivers are permitted to go faster, then protection for vulnerable road users is required with off road or separated provision for their public health protection.




Open PDF

Showing 4 reactions

Please check your e-mail for a link to activate your account.
  • Jeremy Hooks
    commented 2019-10-02 14:20:11 +0100
    > A 4 year old and a HGV or lorry are no more able to share a road when the large vehicle is traveling at 20mph, than when it’s traveling at 30mph.

    If an HGV is sharing a road with a 4 year old, I would suggest it would be inadvisable for its driver to permit it to reach 20 mph or 30 mph. It is a speed limit and not a target.

    > Additionally… Roads are often blocked by queuing traffic.

    Most of our cycle lanes do little for cyclists – they just encourage motorists to pass when there isn’t enough space to do so with safety. However, then the traffic is queuing is the one time they are of some use (they are typically not wide enough to allow a motorist to safely pass a moving cyclist – but they are wide enough to allow a cyclist to pass a stationary motor vehicle).

    > Segregated, protected, lanes for velomobiles, enable their riders and passengers to reach their destination without unnecessary delay, and exposure to the weather.

    Building segregated covered cycle routes is all but impossible with our legacy of narrow roads. But perhaps it should be an aim – particularly for new estates and garden cities… not sure I like the ‘without… exposure to weather’ – one of my favourite things about cycling is being outdoors and exposed to the weather – and I have clothing for when I want to control the level of exposure.

    20 MPH limits are especially suited to residential streets in routes that run parallel to main roads. If I am riding with a 4 year old, that is were I want to be. Personally I think 20 should be the default national speed limit for urban areas (where I live the average speed on A roads is 15mph, so why have 30 or 40 limits?).

    In the countryside, a lot of the roads and lanes have become de facto motorways, often there will be one road between villages, often with no cycle or pedestrian provision. I can appreciate why campaigns such as 20splenty target urban roads, but these roads (that are often inter-urban) should be usable by all cyclists. I use one occasionally, and it is an extremely quiet road, where I will see just a handful of cars over the space of about 5 miles, but there’s always a chance that a driver will come around a blind bend at 60mph (or more). Reading Cycle Campaign had a very enlightening article on their blog a short while ago, from a contributor who lives on the outskirts of Reading – the only route to his son’s school was on a very busy national speed limit country road –

    60mph should only be permitted on country roads if there is extremely good provision for cycling and walking. It should be possible for the vast majority of people to cycle between villages or out of towns and into villages (and vice versa) – or between towns for that matter. As dire as the situation is for urban cyclists, I fear it is much worse for country cyclists – and we have no excuse for letting that be the case.
  • Rod King
    commented 2019-09-23 21:55:10 +0100
    We have no objections to segregated, protected cycle paths. Please continue to campaign for them.
  • Ian Perry
    commented 2019-09-20 23:40:01 +0100
    I disagree. A 4 year old and a HGV or lorry are no more able to share a road when the large vehicle is traveling at 20mph, than when it’s traveling at 30mph.

    This article assumes that all humans are “adults” and have no disAbilities that may affect their judgement and ability to cope with other traffic in the form of large vehicles.

    Additionally… Roads are often blocked by queuing traffic. Segregated, protected, lanes for velomobiles, enable their riders and passengers to reach their destination without unnecessary delay, and exposure to the weather.
  • Rod King
    published this page in Briefings 2019-09-19 19:01:21 +0100