FAQs

Imperial College London's research into the impact of 20mph speed limits suggests they have no net negative impact on exhaust emissions. Results indicated clear benefits to driving style and associated particulate emissions. The research found that vehicles moved more smoothly, with fewer accelerations and decelerations, than in 30mph zones, reducing particulate emissions from tyre and brake wear. We have undertaken an Environmental Evaluation and are satisfied that the lowering of speeds will not have an adverse impact on the environment or air quality. The Environmental Evaluation recommendation was that no air quality modelling was therefore required.

Due to current average speeds, it is unlikely that the lowering of speed limits from 30mph to 20mph will change existing journey times during the day. During off-peak periods, including overnight, some people may experience a slight increase in journey times, however research into the impacts of 20mph by Steer Davies Gleave suggests that introducing 20mph speed limits has a negligible impact on journey times, given that overall journey times are largely dictated by junction delays and not vehicle speeds. We do not expect any changes to be made to bus timetables during the day as a result of the programme. Given the negligible end-to-end journey time impact of the speed limit reduction it is unlikely we will need to make changes to night bus timetables. However we will continue to monitor bus reliability to determine if changes to timetables are needed.

Alongside the self-enforcing measures we are using a mix of other measures to slow speeds, including recalibrating the speed cameras to enforce the 20mph limit, deploying additional traffic enforcement officers on site, and educating drivers on the dangers of speeding. Following monitoring, we will introduce further measures to reduce speeds if needed. There is no evidence to suggest that vehicles are damaged if they approach and pass over speed cushions at an appropriate speed.

The physical measures included in the proposals have been included at locations where speeds are higher than average and there is a higher than average number of collisions resulting in people being killed or seriously injured. The measures, including raised pedestrian crossings, are designed to allow motor vehicles to travel over them safely, and without having to slow down, if driving at a 20mph speed limit. A comprehensive monitoring and evaluation strategy has been developed which will assess the success of the physical measures in lowering speeds. We will use this assessment to decide whether more traffic calming measures are needed and where they should be introduced on other parts of the road network.

Enforcement plays a fundamental role in helping to deliver compliance with speed limits. The Police enforce all speed limits in London, including 20mph speed limits. Almost 160,000 speed offences are processed by the Police each year of which over 42,000 were for offences committed in 20mph limits. To support the roll out of 20mph and to achieve the Mayor’s Vision Zero ambition we’re working with them to enhance this activity with better targeting, new technology, enhanced powers and additional staff which will increase the deterrent effect and reduce the number of people who choose to break the law and put others at risk. TfL and the Metropolitan Police will continue to offer Community Roadwatch across London allowing members of the public to work with the Police to undertake speed enforcement in their local areas. Intelligence on speeding drivers identified through Roadwatch is used to inform targeted police activity and over 32,000 warning letters have been issued to speeding drivers to date. Existing spot speed cameras are in operation on the road network in central London and these will be recalibrated to enforce 20mph speed limits and new cameras will be installed. Our new road danger reduction approach is based on the internationally recognised Safe System. A core principle of this approach is accepting that people will always make mistakes and designing a transport system that ensures death and serious injury does not occur on the transport network when people do. Our work to deliver a Safe System for everyone travelling in London focuses on:

• Safe speeds: lowering speeds to reduce the likelihood and severity of collisions
• Safe streets: redesigning streets to reduce conflict between road users
• Safe vehicles: allowing only the safest vehicles to use our roads
• Safe behaviours: engaging and educating people about travelling safely and enforcing against those that continue to put other at risk
• Post collision learning and justice: learning from collisions and better supporting the people who have been involved

We are delivering marketing, enforcement, training and education campaigns to change behaviours and ensure everyone who uses the road network – people driving, riding or walking – is behaving safely. While speed limits only apply to motor vehicles under the Highway Code, we expect cyclists to travel safely and acknowledge the lower speed limits. Of the speed-related collisions on London’s streets almost all involve motor vehicles and not bicycles. Cyclists behaving in a way that endangers other roads users can be charged with offences. In 2017/18 more than 3,700 people were enforced for cycling offences. The Police can and do enforce dangerous cycling on London’s streets.

TfL does not receive any money from fines issued to people for speeding. This money goes directly to central Government.

There is no evidence to suggest that travelling at 20mph will increase collisions or impact driver concentration. Collision data from around the world is very clear – lower speeds save lives. Research shows that the faster a vehicle is travelling:

• The more likely a collision will occur, because the driver has less time to react, stop and avoid a collision
• The more severe any injury resulting from a collision will be

A speed limit of 20mph has been determined as a safer speed limit for central London because of the high number of people walking and cycling. If a person walking is hit by a vehicle travelling at 30mph they are almost five times more likely to be killed than if they were hit at 20mph.

We did consider the option of variable speed limits, however our data shows that collisions in central London are more likely to occur at night, when free flowing traffic conditions make it easier for vehicles to travel at speed. There are high numbers of people walking and cycling in these areas of central London at night. It is for this reason that we are implementing the lower speed limit at night.

We are working closely with the London Borough of Westminster to create consistent speeds across the City of Westminster. Almost all borough-managed roads within central London already have a 20mph speed limit and we are continuing to work with the central London boroughs where 20mph is not implemented already.