Is increasing sustainable transport, like dieting, as simple as asking individuals to drive less and exercise more? No! Travel structures and societal norms don’t fully support the healthier choices as we’re afraid of injuries and dirty air. Politicians must prioritise road safety to nudge people’s travel choices. 30kph/20mph limits are foundational for mode shift from private car use to feet, cycles and public transport.
The neo-liberal lie is that “the market fixes itself”. This is largely why there are too many cars. Individuals have been left to fund their own transport rather than collectively investing in public transport via taxes to solve the jams and create healthier communities. The revolution in public health and liveability won’t come through engineering. There aren’t the engineers or time. Wide-reaching, population-level public health initiatives are needed now. We know what to do. The block is political! Politicians must prioritise road safety and ecological travel like walking, cycling, and public transport – buses, trains, trams etc. Investing in slower speeds first pays back fast!
Fear tops people’s concerns in getting about. Common reasons not to cycle are fear of a crash or abuse. Raising confidence in using our legs is essential. System-wide better road safety is key to behaviour change.
The foundational fix is a default 30kph/20mph limit in built up areas and is supported by some 70% of the population. Slower limits reduce the power imbalance between road users so that some drivers will choose to drive less. The difference in impact speeds is a 7-10 times safety benefit in fewer fatalities. Casualties fall by 20+%. When speed drops, even a bit, risks hugely reduce – 1mph less in towns is 6% fewer injured. At 50kph/30mph half of 60+ year olds die if hit.
Likelihood of severe or fatal injury for pedestrians struck by drivers traveling at these speeds
A 30kph/20mph default is a very inexpensive policy, and especially cost effective when implemented at national level (approximately eight times less than at local level). Overall motoring trip times are not significantly altered, with journey times predominantly determined by time stope in congestion/junctions. However, the trip time fact isn’t obvious and warrants explaining to motorists.
Exercising more happens when confidence in our own ecological travel and in allowing vulnerable people to travel actively or use public transport rises. The first and last mile of any public transport trip tends to involve walking for instance. No matter how good in quality, frequency or price, buses or trains are, if the walk to them feels scary then some are put off.
Enforced 20mph limits work ideally with a Vision Zero policy (no deaths or serious injuries). Key are strong enforcement and penalties on speeders, drink, drug or tired drivers and phone texting. Such street bullying is as harmful at societal public health level as other violence that society would never tolerate. In-car speed limiters become law for new cars in 2022. These set the pace of traffic behind.
Community activism can also act as a powerful catalyst to enhance local streets with place-making and community ownership. Crucially, communities will support and vote for politicians who promise better road safety with sticks and carrots for green transport change. Why 20mph supports traffic reduction is also set out at http://www.20splenty.org/traffic_reduction and Vision Zero (that no serious casualties or deaths are acceptable) at http://www.20splenty.org/vision_zero
 Tefft, Brian C. Impact Speed and a Pedestrian’s Risk of Severe Injury or Death, AAA Foundation for Traffic Safety, Washington DC, September, 2011