Bus impacts from London wide 20mph speed limits
Request ID: FOI-1144-1819
Date published: 18 September 2018
You asked
When buses are slower, it takes more bus resources to maintain the same bus frequencies and or route length. It is therefore improbably that the proposed London wide 20mph speed limits will not severely impact upon bus resources.
Via FOI or EIA regulations, please provide any assessment TfL has produced on the bus network impacts of the proposed London wide 20mph speed limit and earlier phases of it such as for the congestion zone.
This is of particular concern for outer London routes where speeds are faster during the day, but also for off peak and particularly night routes, which rely on faster speeds to maintain high frequency services at this time.
I highly doubt for example that the 15mile N279 service from Waltham Cross to Trafalgar Square that serves my house can maintain three buses per hour all night with current resources if it trundles along at 20mph despite empty roads. A 10mph reduction to the service will increase journey time by at least 15mins and I am not aware of one person who has been killed by a night bus, though many who have been provided a safe and secure route home. With 12min turnaround times at the end of each journey, this increase would likely force the operator to reduce the service to 2 buses per hour if the same resources are available. This means a massive cut in profit for bus companies resulting in reduced investment and far less bus journeys as people opt for other options, which will ultimately result in more taxi and car journeys.
Road safety needs to be balanced with other considerations
We answered
TfL Ref: 1144-1819
Thank you for your email received by us on 24 July 2018 asking for information about 20mph speed limits and their impact on bus services in London.
Your request has been considered in accordance with the requirements of the Freedom of Information Act and our information access policy. I can confirm that we hold the information you require. You asked for the following:
please provide any assessment TfL has produced on the bus network impacts of the proposed London wide 20mph speed limit and earlier phases of it such as for the congestion zone.
While we did not produce a specific assessment on bus network impacts, I can advise that bus speeds were considered as part of the analysis for the current 20 mph proposals. Initially, average night bus speeds (excluding dwelling time) were examined along approximately one km stretch of road and one of the areas under consideration exceeded 20mph. However, it should be noted that spot speeds - the instantaneous speed of a vehicle at a specified location - may not rise above 20 mph at certain points along the road. Additional analysis looked at the fastest stretches of road that were approximately 50m in length. This analysed general traffic within each larger section and the speeds reached, which we would also assume reflects the speeds reached by buses. Unsurprisingly, excess speeds were noted to be higher the bigger the distance away from London.
Turning to the N279 bus route mentioned in your request that travels outbound from the Inner Ring Road, down the A503 corridor and along Hampstead Road through Camden. I can advise that there is an existing 20 mph limit in place. The N279 proceeds to Seven Sisters, passing briefly onto the A10, followed by the A1010 High Road, a local authority managed road, which already has a 20 mph limit on the first section within Haringey before reverting to 30mph at the boundary with Enfield.
The principal stretch of the N279 route that would be affected by the proposals is located between Camden and Seven Sisters. Roughly 50m stretches of road with the highest average speeds identified here range from 24 mph to 28 mph, although most speeds are between 24-25 mph. Between Seven Sisters and Bruce Grove, speeds consist of 20-23 mph.
Taking the above factors into account, a moderate drop in bus speeds along a few specific sections where they are able to exceed 20 mph might be expected. However, it is probable that much of the impact would be mitigated through smoother driving and signal timing adjustments.
As more detailed plans are developed for implementing the proposals, due consideration will be given to any requirements for engineering to ensure routes are self-enforcing and the potential impacts on buses minimised.
As for previous 20 mph trials on the Transport for London Road Network (TLRN), the following slide shows the expected impact on buses using the Southern River Route, also known as the A3200 York Road that has a 20 mph limit; the rest of the Route consists of local authority managed roads.
There was also a specific focus on bus running times after the implementation of 20 mph speed limits on Bishopsgate and Farringdon. Whilst night bus speeds were not a part of this study, the analysis shown below demonstrates that there was no impact on daytime bus service performance.
Additionally, general traffic spot speeds were analysed for the remaining trials. Results were mixed with outcomes appearing to be considerably more influenced by other factors, such as road works in the vicinity, rather than the lower speed limits. This was partly due to speeds already being close to levels suitable for a lower speed limit.
Our various Congestion Charging impact monitoring reports for earlier studies of speed analysis may also be of interest at:
https://tfl.gov.uk/corporate/publications-and-reports/congestion-charge
In accordance with section 21 of the FOI Act, we are not obliged to supply you with a copy of the requested information as it is already accessible to you elsewhere.
Turning to your comment that ‘road safety needs to be balanced with other considerations’, we would like to stress that safety will always be our top priority. The Mayor’s Transport Strategy sets out his ‘Vision Zero’ approach of eliminating deaths and serious injuries from our roads by 2041, and measures such as 20mph speed limits and our wide-ranging bus safety programme will be important in helping us achieve this.
https://tfl.gov.uk/corporate/safety-and-security/road-safety/vision-zero-for-london
https://tfl.gov.uk/corporate/about-tfl/the-mayors-transport-strategy
If this is not the information you are looking for, or if you are unable to access it for any reason, please do not hesitate to contact me.
Please see the attached information sheet for details of your right to appeal as well as information on copyright and what to do if you would like to re-use any of the information we have disclosed.
Yours sincerely
Jasmine Howard
FOI Case Officer
Information Governance
Transport For London
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