Author Dr Sarah Jones, THINK Co-Director from Public Health Wales
The COVID-19 pandemic has been the greatest threat to health and health services since at least the emergence of HIV in the 1980s, but arguably for longer. Recovering from it is a significant challenge on an individual and population health level, as well as for health services.
Even before COVID-19 emerged, there was strong evidence that a reduction in the default speed limit, from 30mph to 20mph, in “urban” areas, could have significant benefits for public health (Jones and Brunt, 2017). Post-COVID-19, 20mph has even greater potential to benefit public health. It could well be the most significant public health intervention in the UK since the indoor smoking bans of 2006-7 and, with time, could even surpass the gains that these have achieved.
In September 2023, it is intended that the default speed limit in Wales will be reduced to 20mph. This is likely to make a significant contribution to the COVID-19 health and health services recovery, but also to tackling the incalculable harms associated with motor vehicle transport, to addressing the climate emergency and to narrowing inequalities.
This article outlines the link between 20mph and the COVID-19 recovery.
Transport related harms
Transport and travel are fundamental for societal development and evolution. Roads have been used, with harms and benefits, for over 12,000 years, but the harms have increased significantly in the past 100 years, as cars have become more affordable and available to more people.
Roads facilitate trade, development and communication, potentially benefitting health and wellbeing. But, they also cause and exacerbate injury, illness, disease and inequalities, help the spread of infection, and increase mental health harms.
COVID-19 is, for most people a mild to moderate respiratory disease, but a wide range of other symptoms can occur, including fatigue or neurological symptoms, and long term disability or death can result (WHO, 2022a, b). Developing robust treatments for the short and long term effects of COVID-19 is a still at an early stage, but should include avoiding further cardio-respiratory stress, along with symptomatic relief associated with light to moderate exercise (Daynes et al, 2021).
Health services also need “treatment”. Elective waiting lists have risen, COVID-19 cases may need in- or out-patient treatment and health services need to deal with new, urgent or emergency health needs. Health services staff also need to recover from the intensive and uncertain demands COVID-19. A substantial proportion of the new, emergency or unscheduled needs are linked to avoidable harms associated with the transport environment, including road traffic injuries, poor air quality, physical inactivity, mental health harms and noise. Reducing the incidence and prevalence of these transport related health harms has the effect of reducing the demand for health services or “lowering the baseline” (Bhopal et al, 2020).
What has all of this got to do with 20mph?
In short, and primarily, 20mph should reduce crashes, casualties and fatalities on our roads because the lower speeds will reduce the risk of crashing and the risk of serious injury should a crash occur (OECD, 2014; Grundy et al, 2009; Webster and Layfield et al, 2007). This alone will have the “lowering the baseline” effect.
But, 20mph should also encourage smoother driving (NICE, 2017) and with less acceleration and braking (reducing from 30mph to 20mph means 33% less of both), then pollution should also decrease (Archer et al, 2008). Hard acceleration may increase nitrogen oxide emissions (NOX) by two to four times compared with a constant speed (Jourmard et al, 1995). At worst, evidence suggests no overall change in pollution levels relative to 30mph (TEAG, 2013).
20mph can also increase walking and cycling; evidence from Bristol has suggested a 12% increase post-introduction (Bristol City Council, 2011; Dorling, 2014). People prefer to walk and cycle along lower speed roads (Grudgings et al, 2021) and may be reluctant to walk or cycle because of the perceived risks associated with speeding traffic (Jacobsen et al, 2009).
Increasing walking and cycling has many benefits; less air pollution from the short journeys that people can swap from car to active travel (Frank et al, 2000; Krzyzanowski et al, 2005), therefore causing and exacerbating less respiratory disease. It also increases physical activity and reduces the harms of inactivity including cardiorespiratory problems, obesity and poor mental health (WHO, 2020).
20mph also reduces noise pollution (Lawton et al, 2012); vehicles travelling at lower speeds have less engine noise and produce less noise at the tyre / road interface. The health effects of noise pollution are more difficult to quantify than those for air; it is an under-estimated and poorly understood public health problem and there is also an overlap in outcomes that means identifying the independent effects of noise from air is difficult.
But, evidence suggests that the burden of traffic noise on health is significant and similar in type and magnitude to air pollution (Stansfeld, 2015). Much of this is linked to annoyance and sleep disturbance, but these can lead to outcomes including ischaemic heart disease (EEA, 2022). Across Europe, an estimated 48,000 new cases of heart disease and 12,000 premature deaths each year are due to environmental noise, much of this from road traffic. Therefore, less noise will make a substantial contribution to lowering the post-COVID burden on health and health services.
Beyond reducing the direct car related harms to health, there are wider implications of 20mph for the economy and employment. Evidence suggests that a 20mph speed limit encourages small business viability (Dorling et al, 2014; Carmona, 2018). This is likely to be due to numerous factors, such as drivers and passengers in slower moving vehicles are more able to see what local shops sell, but also that lower vehicle speeds make walking and cycling to shops more attractive. People who walk, cycle or use public transport to visit shops spend 40% more per month than car drivers (Carmona, 2018).
20mph may also make a significant contribution to the “holy grail” of public health; narrowing inequalities. This is because those living in the most deprived areas are more likely to be killed or injured on our roads (Dorling, 2014). Vehicles travelling in the most deprived areas have higher average speeds and a greater proportion of vehicles exceeding the speed limit (MacGibbon, 1999; Stevenson et al, 1996; Mueller et al, 1990; Haddon et al, 1961). Traffic volumes and variety of vehicles, both of which increase injury risk, are also influenced by deprivation (Roberts et al, 1995a; Paulozzi, 2005). These speed, volume and type effects contribute to the higher risks of injury and injury rates from road traffic crashes in the most deprived areas.
Finally, and relating to more recent pressures, evidence also suggests that 20mph is associated with a 12% decrease in fuel consumption (Hass-Clau, 1990). Reduction in fuel consumption is critical not only for reducing pollution, but also for mitigating climate change and recognising the fragility of global oil and energy markets.
COVID-19 forced us all to “slow down”; prior to that, the concepts of speed and economic growth were entwined and the dominant paradigm was that travelling quickly promotes economic growth (Christie, 2018). Economic growth needs a healthy population; achieving that needs us to recognise the opportunity that COVID-19 has brought and to more widely embrace the slow down.
20mph is a public health intervention that is unusual in that the evidence base suggests only positive health benefits (Jones and Brunt, 2017). The apparent “slow down” that it brings offers us the opportunity to speed up the COVID-19 recovery and, given the breadth of evidence based effects, see the greatest public health gains since the smoking ban.
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