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.

To introduce safer speeds on our roads as quickly and consistently as possible, we will be lowering the speed limit with signs and lining changes only at first.  A comprehensive monitoring and evaluation strategy has been developed which will assess the efficiency of the programme 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.  This will allow us to direct limited resources to the areas of the network where road danger risk is highest.

The physical measures included in the proposals already 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. 

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. 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. 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 offencesThe Police can and do enforce dangerous cycling on London’s streets.

The MPS will designate police constable traffic enforcement powers to police community support officers so they can stop speeding vehicles and take enforcement action against drivers. 

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 many roads in 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.

Current collision monitoring from phase 1 of the lowering speed limits programme shows over 125 fewer collisions occurred in central London since the 20mph speed limit was introduced.  No fatalities or serious injuries have occurred on these roads since the 20mph speed limit was installed.   Collisions involving those walking, cycling or using a motorcycle have decreased by almost a half. 

We work closely with the London Boroughs to create consistent speeds across the both the borough road and TfL road networks.  Over half of all London roads already have a 20mph speed limit and we are continuing to work with the London boroughs where 20mph is not implemented already.

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
• 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.

Once the speed limit has been reduced and we have monitored and assessed the effectiveness of the speed limit change, we will seek to introduce further measures where appropriate which may include:

• Raised pedestrian crossing points
• Speed tables
• Lane reallocation (cycle lanes, bus lanes, footway extensions)
• Lamp column mounted banners
• Planting and green infrastructure changes