Lower residential speed limits: let’s stop the “car”nage

The City of Sydney recently announced it would be lowering the default speed limit from 50 km/h to 40 km/h on all regional and council roads within its council area. Additionally, the city centre and other high activity areas with lots of pedestrians, cyclists and scooters are being considered for reductions to 30 km/h, putting them in line with some school zones and Centennial Park among others. This edict has unsurprisingly been challenged by motoring groups, industry and Premier Minns, who commented, ‘You could walk quicker than that’ and ‘Sydney shouldn’t be treated as a country town’. Aside from rankling residents of regional NSW, given average walking speeds are 5-6 km/h, perhaps Premier Minns was still thinking about the Olympic 100m where sprinters average around 35 km/h?

The arguments for and against lowering speed limits in urban areas are well-documented. The primary motivation is safety, not just for pedestrians, cyclists and other vulnerable road users but all road users. Higher speeds increase both the risk of a crash due to limits on our ability to react in time (typically one second to an unexpected event) and severity because kinetic energy imparted increases with the square of the speed[1]. According to the World Health Organisation a pedestrian hit by a car at a speed of 50 km/h has a roughly 20% chance of survival, with odds improving to 75% (40 km/h) and 90% (30 km/h). If they’re hit by our growing population of SUVs, delivery vans and electric vehicles (much heavier as well as much quieter), the odds are stacked further against. Research conducted by the University of Sydney using 12 years of accident data for NSW from 2010-22 suggests that pedestrians comprise around 15% of fatalities despite travelling ten times fewer kilometres than the typical car[2]. Roughly half of all pedestrian/vehicle accidents result in a fatality/serious injury with one-third of these accidents occurring on 60 km/h roads and half occurring on 50 km/h roads. Additionally, the data show the relative risk of a fatal/serious accident reduces dramatically with lower speed limits – for instance dropping from 60 km/h to 50 km/h reduces relative risk by 30%, while dropping to 40 km/h reduces relative risk by 45%.

Additional arguments for lowering speed limits point to the potential fuel savings and environmental benefits of lower speeds. The relationships between vehicle speed, fuel consumption and emissions are highly complex and vary by vehicle make, model and vintage, but generally a speed of around 40-50 kph is considered ‘optimal’ although this overlooks the stop/start nature of urban driving. Noise is evidently reduced with lower speeds.[3] What is more irrefutable, is that slower speeds present a more amenable environment for cycling and walking, promoting active and healthier lifestyles in our continued battle with sedentarism. This has become particularly acute for our younger and older populations; on the one hand trying to reverse trends against driving children to school, on the other maintaining healthy aging for whom walking is the number one form of exercise.

The vocal naysayers point to economic impacts of increased travel and delivery times, along with increased potential for driver frustration, non-compliance and enforcement challenges. It is true, if we lower speeds, travel times will increase adding what amounts to a few minutes for the typical Sydney commute. Considering the average speed in Sydney is 30-40 km/h, dropping to as low as 20 km/h during the peak, this doesn’t seem like a game-changer. Motorists will adapt or fill government coffers with fine revenue, many will still recall when default residential speed limits were 60 km/h. Realise also, we are talking very much about local streets, once the domain of children playing in the street or riding a bicycle without fear of being hit.

Premier Minns also spoke about Sydney as having “broader obligations than just those people that live and pay rates within its boundaries ... it's a major international city,". The reality is Sydney is sadly lagging well behind many ‘major international cities’ in adopting lower urban speed limits including London, Edinburgh, Paris, Rome and Stockholm. This is working directly against efforts to improve the liveability of this great city, compromising state and local government Movement and Place initiatives. We are now seeing whole countries take a stance, with Wales adopting a default 20 mph limit in 2023 and Scotland set to follow suit in 2025. Australia, with some of the highest default speed limits in the developed world is a notable non-signatory of the “Stockholm Declaration” adopted by 130 countries in 2020, advocating 30km/h limits in urban areas where “vulnerable road users and vehicles mix in a frequent and planned manner.”

Perhaps it would be naïve to suggest that reducing speed limits alone offer a silver bullet solution. Many of our residential streets are wide with design speeds of 50-60 kph, creating a mismatch with lower speed limits. Generally, we have tried to address this through the installation of bone-jarring speed bumps and other ‘traffic calming’ fixes, which make travelling by cars, buses and bicycles unpleasant. Given a choice, perhaps we would all sacrifice a few kilometres of speed for a more pleasant ride, while simultaneously creating environments that are more pleasant for walking and cycling.

For the sake of our city and our children, let’s stop the ‘car’nage and lower residential speed limits.

References

[1] https://www.itf-oecd.org/sites/default/files/docs/speed-crash-risk.pdf

[2] https://www.transport.nsw.gov.au/system/files/media/documents/2023/mbnov2023_01122023.pdf

[3] https://www.sciencedirect.com/science/article/pii/S0160412022005785