20 miles per hour 


From 2012 – 2014, So-Mo supported Liverpool City Council to roll out its flagship 20mph scheme. We focused on drawing out behavioural insights into attitudes, beliefs and behaviours prior to implementing any campaign activities or installing any signs.

Since then we have been supporting many local authorities to implement their own 20mph schemes, acting as a trusted advisor, training provider, and providing easily replicable campaign activities. In addition to Liverpool City Council, further clients have included City of Edinburgh Council, Birmingham City Council, and Bristol City Council.

The Challenge

As self-compliance is the main objective of 20mph, simply installing 'signs and lines' to encourage 20mph would not have been enough to achieve reductions in speed. Our insights revealed that, although the public supported the introduction of lower speeds, they did not have clearly formed ideas or beliefs about 20mph.

An example of this is Drivers, who tended to overestimate their own driving abilities and underestimate the abilities of others, or in other words, they saw others as the problem. In partnership with Merseyside Police, we engaged with speeding drivers and found that they displayed cognitive dissonance, an uncomfortable tension between two simultaneous and conflicting ideas or feelings. They realised that in speeding near schools they had engaged in a behaviour inconsistent with the type of person they perceive themselves to be and would like others to perceive them as. A fear-based message was going to be rejected by people in this mental state.

Our approach

We use a combination of methods to achieve 20mph, concentrating on three key approaches scientifically proven to influence outcomes:

· Behavioural – we made speeding drivers mindful of their risky behaviour, giving them ways to urge others to drive slower. Public commitment of this sort put speeding drivers in a ‘hypocrisy condition’, and subsequently showed greater attitudinal shift than those who were only reminded that they had driven at speed or merely made the public commitment.

· Attitudinal – we ‘amped up the good’ by harnessing extensive national, local, and social media featuring influencers and local people to ensure that the social norm was set at positive and compliant to 20mph.

· Informational – we designed ways to ensure people knew why the speeds were being introduced, and in particular, that the new speed limits were mandatory and that the police could and would enforce the new limits.

The Results

In the Atkins 20mph Research Study published by the DfT in 2018, Liverpool’s 20mph scheme was selected as a particularly great example of a behaviour change scheme. As far as we are aware, Liverpool’s 20mph scheme had the lowest number of objections to the Traffic Regulation Order process. Speed reduction is currently under evaluation.

In Bristol, a statistically significant reduction in average traffic speeds of 2.7mph has been found since the introduction of the 20mph scheme. Additionally, reductions in the number of fatal, serious and slight injuries from road traffic collisions, equating to estimated cost savings of over £15 million per year.

If you would like to learn more or discuss something similar, please do not hesitate to email us.