How about setting the speed limit to 40 kmh on the white roads and 50 kmh on the light brown ones (excluding motorways and CBD)? Inner northern suburbs, Melbourne

I made the point recently that cars will almost certainly be the majority mode in Australian capital cities for a long time to come; so politicians and lobbyists needs to start actively managing private transport rather than hoping it will magically go away (see Can we have a mature discussion about the future of urban transport?).

I identified a range of possible actions to “tame” private transport, including higher fuel efficiency standards, congestion pricing, and revised penalty and enforcement regimes. This time I want to look more closely at one of those actions; substantially lower speed limits.

Here’s a simple proposal; reduce the speed limit to 50 kmh on urban arterial roads and 40 kmh on all others, starting with the inner suburbs. The exhibit indicates how this might work in inner Melbourne. It shows the region within 10 km due west, north and east of Melbourne Town Hall. The light brown roads outside the CBD – the arterials – would be subject to a maximum speed of 50 kmh at all times. The white roads, plus all CBD streets, would have a maximum speed of 40 kmh at all times. The dark brown roads – the motorways – would be unchanged.

Why do it? Lower maximum speeds will improve safety for pedestrians and cyclists; the risk of a pedestrian dying if struck by a car travelling at 40 kmh is around half of that for a car doing 50 kmh and a third for a car doing 60 kmh. A slower maximum speed would improve the amenity of neighbouring land uses, promote roadside activity, and reduce pollution and emissions. It would also simplify the rules by eliminating the need for special speed zones around schools and in strip shopping centres.

A very high proportion of the streets in Melbourne’s inner northern suburbs are lined with dwellings and businesses that generate pedestrian activity. Many are narrow and carry much more traffic than they were originally designed for, especially east-west streets. There’s lots of building activity in this region and densities are increasing. The profile of the population is changing too; residents like the public realm. They like to get “out and about” and ride bicycles.

This is not an outlandish idea. The Heart Foundation (SA) says there are plenty of precedents:

In South Australia, the speed limit around some schools has been set to 25 km/h in recognition of pedestrian vulnerability. In Unley, a 40 km/h limit on all local streets has been in place since 1999 as well as in numerous other suburbs in Adelaide such as Bowden/ Brompton and North Haven. In some Melbourne suburbs and also on main roads through shopping precincts a 40 km/h speed limit has been applied. Brisbane CBD is now a 40 km/h zone. European cities such as Sweden, Germany and Britain are implementing 30 km/h speed limits on residential and shopping strips as world’s best practice.

The key downside is slower speeds and the consequent economic loss in passenger and freight travel time. It’s a real issue but I think the scale of loss would be small. While cars, buses, trams and trucks can go fast for short periods, average speeds by road are considerably lower than the current maximum even in the interpeak and evening periods. These are inner suburban streets where drivers deal with many intersections, traffic lights, parked cars, and others vehicles competing for the same road space. Many strip shopping centres in this region already have 24 hr 40 kmh limits.

The findings of a Monash Accident Research Unit project support this view. Archer et al concluded that a reduction in average travel speed brought about by reducing urban speed limits is only likely to have a marginal impact on travel time:

Research tends to support this notion given that average speeds are influenced by many other factors including driver attitudes and preferences; roadway design; forms of traffic regulation at intersections; and prevailing traffic conditions (levels of congestion; weather; etc). Research studies in Australia in relation to the then proposed reduction of the default urban speed limit from 60 to 50 km/h, indicated only minimal impact on individual travel times and large benefits to society as a result of the reduction in crash trauma.

We shouldn’t be shy about modestly slower average speeds for cars, trucks and buses. Public transport is substantially slower end-to-end for the great majority of trips than private transport, yet governments are investing in improvements because it has social advantages (see What’s government done to make public transport better?). We should use the same logic to justify lower speed limits for roads i.e. the amenity, safety and environmental benefits of slower traffic are likely to exceed the time costs. In any event, the biggest time losses would be in the evenings when on average the value of travellers’ time is relatively low. There’s also an argument that the value of travel time might be significantly over-stated in transport analysis.

Getting the maximum benefit would require strong enforcement and penalties that incentivise appropriate behaviour. Inevitably though, the full benefits will only be realised if governments build traffic calming works. There’s an opportunity here for the Federal government to give substance to its cities policies by establishing a flagship multi-billion dollar fund to build traffic calming works in partnership with state and local governments.

Yes, a 40/50 kmh limit would be very difficult politically. It might be necessary to start with a smaller area – say the first 5 km from the CBD – or start in selected suburbs where residents are more receptive. Perhaps setting a 50 kmh limit on a multi-lane arterial like Bell St is too ambitious at this time. But private vehicles already account for 90% of all motorised travel in Australia’s capital cities; politicians and lobbyists need to get serious about “taming” cars.