London is going harder to get traffic speeds down in the city, expanding its 20MPH (32kmh) zones as well as planning a much more extensive redesign of streets for a slower and calmer traffic environment.
A new network of 20MPH streets is being rolled out in the congestion charge zone in inner-London and speed cameras are being installed to enforce the new limits.
Last year almost 39,000 drivers were pinged and fined by the cameras on the existing network.
Now Transport for London (TfL) is moving to the next phase involving a further 140 kilometres of the road network in inner and outer London, including on the inner ring road, high-risk roads and roads in town centres.
This time it will be looking at a range of measures beyond speed limits, and critically, it will take existing and potential bike riding volumes into account, something that should automatically be done in Australian roads management, but is rarely considered.
"We've completed a risk analysis to identify roads in inner and outer London where speeds should be lowered to reduce the risk of road users being killed and seriously injured, focusing on town centres and roads with the highest risk of a collision occurring," TfL says.
The risk analysis considers:
- the number of deaths and serious injuries that have occurred on the road
- the current levels of walking and cycling and predicted future levels of walking and cycling
- speed limit of surrounding streets
- if the road has a town centre, or another location with high volumes of people walking or cycling
- if lower speeds on TfL roads would increase traffic in local streets
This might mean speeds will be lowered along some roads from 50MPH to 40MPH, or from 40MPH to 30MPH.
"There are many different ways to encourage people to drive at lower speeds, but evidence shows that self-enforcing speed limits are the most successful way to reduce speeds,” TfL says.
"A self-enforcing speed limit means that people are more likely to drive within the signed speed limit because they feel it's the easiest and safest speed to drive along that road."
"This is generally because of the way the road looks and has been designed."
Some of the design and engineering measures used to lower speeds are:
- Road markings
- Speed cushions
- Speed bumps
- Raising pedestrian crossings
- Widening footways for people walking
- Giving more space to people cycling
- Removing the white line in the centre of a road
- Changing the surface of the road
- Creating curves along the road that requires vehicles travelling in different directions have to slow down or give way
- Introducing more traffic islands in the centre of the road
- Placing trees, planters and parklets along the roadside or in the centre of the road
"There's no 'one size fits all' approach to reducing vehicle speeds," TfL says.
"We use different measures depending on the type of road, who uses the road and the road space available."
"We'll continue to monitor the effectiveness of these measures in lowering speeds, so we can determine if more design changes are needed."
Effect on traffic and pollution
Imperial University's evaluation of 20MPH zones in London shows they have no net negative impact on exhaust emissions.
It also shows that in 20MPH zones vehicles move more smoothly, with fewer accelerations and decelerations, than in 30MPH zones. This smoother driving style actually reduces particulate emissions from tyre and brake wear.
Interestingly, London authorities have faced pushback on the lowering of speeds as some drivers thought emissions would be higher if speeds were lower.
But a study of the 20MPH zones by Imperial University found there is no net negative impact.
It also shows that in 20MPH zones vehicles move more smoothly, with fewer accelerations and decelerations, than in 30MPH zones.
This smoother driving style actually reduces particulate emissions from tyre and brake wear.