Do slower speeds cause congestion and pollution?

    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.

    Will journey times including those for buses increase and will this lead to inconvenience and extra cost for businesses?

    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.

    Will the self-enforcing measures not slow traffic, be uncomfortable for passengers and lead to more vehicle wear?

    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.

    Are more physical measures needed including more crossings and segregated cycle lanes?

    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.

    Is better enforcement needed for better road user behaviour?

    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.

    Is it just to raise revenue?

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

    Will it lead to more accidents?

    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.

    Is it not needed at night or quieter times?

    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.

    Do we need consistency in speed limits?

    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.

    How will you deliver lower speed limits?

    Department for Transport (DfT) guidance suggests that streets that are self-enforcing are the most successful way to achieve compliance with lower speed limits. In addition, the look and feel of roads that are designed to be self-enforcing often mean they’re more welcoming places for people to walk and cycle.

    However, the roads we manage are London's most strategic routes, carrying 30% of all London’s traffic and providing important links for freight and servicing vehicles, as well as buses. They’re also often relied upon by emergency services as the most direct roads to use when responding to an emergency. 

    There's no 'one size fits all' approach to reducing vehicle speeds and we also need to consider the type and function of the road, the space available and different road users, when we design a low speed environment.

    The Mayor is keen for TfL to deliver the benefits of a lower speed limit as soon as possible.  Therefore, in the first instance, our work will involve:

    Work involves:

    • Installing new speed limit signs and road markings
    • Recalibrating all existing speed cameras to enforce the new lower speed limit
    • Signs and temporary lamp post banners
    • Regular speed limit signs are installed at the entrance to roads indicating the speed limit, as well as repeater signs along the road. These are standard measures when indicating speed limits and in with DfT guidance

    The Police will continue enforcing all speed limits across London, including where new speed limits are in place. The Police enforce all speed limits in London using on-street officers, mobile speed cameras and fixed speed cameras.

    We will be closely monitoring the effects of these schemes on vehicle speeds thorough a variety of methods such as speed surveys and Healthy Streets environmental surveys.  

    The introduction of the lower speed limits will be supported by a marketing campaign to increase awareness of the new limits. This will be before the new speed limits are introduced.

    20mph will cause more congestion and slow down journeys

    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.

    It will not help active travel or promote walking and cycling

    Research suggest that nearly a fifth of Londoners feel that too much traffic, and traffic travelling too fast, are major barriers to walking[1]; and over half say that fear of being in a collision is a major barrier to them cycling[2]. 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.  Public consultation for earlier 20mph schemes suggest that over half of those who responded believed that the proposals would have a positive impact on walking, almost two thirds said that the proposals would lead to more people cycling and over 40% thought that the proposals would encourage people to walk or cycle instead of using a motor vehicle.  Four in ten thought that the proposals would have a positive impact on public transport, with 19% saying they would choose to travel by public transport.

    Pollution will increase as cars go slower

    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.

    There will be an impact to bus journey times

    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.

    What has TfL delivered so far?

    We successfully introduced a new 20mph speed limit within the central London Congestion Charging zone in March 2020 following positive public consultation the year before. We have introduced a 20mph speed limit on over 80km of TLRN including the central London congestion charging zone and other key corridors including A10 in Hackney, A1 in Islington and A3220 Earls Court Road. 

    Half of the 2,000 people that responded to the consultation said reducing the speed limit would have a positive impact on walking with 31% saying that many more people would choose to walk. Almost two-thirds thought that the proposals would lead to more people cycling (59%).