Among urban and village improvement options, 20mph ranks top for cost effectiveness. Over a wide area, 20mph benefits all road users and the whole community. Casualties fall 20%[1], noise almost halves and active travel rises. Councils can afford it.

[1] http://www.20splenty.org/20mph_casualty_reduction

Councillors choosing how to improve their locality must compare their options on both popularity and value for money. Wide area solutions such as 20mph limits offer far more utility than location specific works as small improvements for many people outweigh large benefits for a few.

With a cost of approx. £3 per head of population the benefits are huge :-

Speeds on faster pre-speed roads fall most (6-7mph). Average falls for roads were 1.3mph in Portsmouth, Warrington 1.45mph, Calderdale 2.0mph and Bristol 2.7 mph. Some roads are exempted.  Everyone benefits across the network from fewer crashes. Casualties reduce 20% network wide. Physical activity levels rise. It resets the consensus on how we drive in situations where people and motor vehicles mix.

For the cost of 20mph for a 200,000 person population (£600k), a transport shopping basket would contain just four traffic controlled junctions (at £150k) or 13 puffin crossings (at £45k)[1]. 

Wide area 20mph limits are seven times more cost effective per mph reduced per mile of road than isolated zones with physical calming[2]. They are five times more cost effective than targeted interventions on A roads to cut killed and serious injuries[3]. Implementation costs are typically under 1% of yearly casualty and physical inactivity costs[4]. Bristol report the estimated total number of injuries avoided across the city each year as 4.53 fatal, 11.3 serious and 159.3 slight injuries. The estimated annual saving to society from fewer casualties is £15.250 million[5]. The do nothing option costs more to society than bringing in 20mph limits.

The key difference between wide 20mph limits and all other highways options is its scope. 20mph brings door to door improvements with long lasting changes to a community and people’s habits, for a once off cost. 20mph improves safety, perceptions of risk and encourages healthier travel choices. 

70% of people say 20mph is right for where people live. Phil Jones, Cabinet Member for Transport in Camden said

“20mph is the most popular decision I ever made”.

Rod King MBE Founder and Director of 20’s Plenty for Us said

“20mph is the value for money winner for quality streets. A default 30mph limit no longer delivers what communities need. Once councillors understand the benefits they all choose 20mph and their constituents thank them for it with increased support. 20mph is a popular policy that pays back quickly.”

[1] Highway works costs from https://www.trafficchoices.co.uk/index.shtml  https://www.wiltshire.gov.uk/highways-works-cost https://bit.ly/2Vk9kQh

[2] http://www.20splenty.org/20mph_limits_vs_isolated_20mph_zones

[3] http://www.20splenty.org/5x_better_than_targeted_interventions

[4] http://www.20splenty.org/casualty_and_physical_inactivity_costs

[5] http://uwe-repository.worktribe.com/OutputFile/875556

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