Tories on the London Assembly argue new 20mph zones have caused unnecessary delays on buses but Sadiq Khan denies this, reports Noah Vickers, Local Democracy Reporter

Sir Sadiq Khan has insisted that the roll-out of 20mph limits on roads across the capital is not slowing down average bus speeds, despite the fact that buses remain slightly slower than they were pre-pandemic.

In answer to a recent written question, the mayor said it was “unlikely” that the rising number of 20mph roads was having more than a “negligible” impact on bus speeds – as “overall journey times are largely dictated by junction delays”.

As part of Khan’s ‘Vision Zero’ strategy – which aims to eliminate all deaths and serious injuries from London’s transport network by 2041 – Transport for London (TfL) has increased the number of 20mph limits on roads it controls, so that some 164 miles are now subject to the speed cap.

But Tories on the London Assembly argue that the policy has caused unnecessary delays on buses, creating a “long-term cycle of decline” where buses become less attractive to Londoners because of how slow they are, and consequently less financially viable for TfL – leading to routes being cut.

Neil Garratt, leader of City Hall Conservatives, wrote to Khan: “There’s clear evidence that bus speeds are declining across London. What work have you done to determine whether lowering speed limits is a possible factor?”

The mayor replied: “The average bus speed in London in 2019/20 was 9.29mph and in 2023/24 was very similar at 9.27mph – a very small decline of 0.02.

“However, as a customer there is a perception of declining bus speeds following returning traffic and roadworks after the Covid-19 period.”

A report by the watchdog London Travelwatch revealed in November last year that in parts of central London, bus speeds have dropped below 7mph.

The research found that average bus speeds range from 8.1mph in inner London to 10.3mph in outer London. Bus speeds were lower in every borough in 2023/24 compared with ten years previously. In the ‘square mile’ of the City of London, buses travel at only 6.6mph – and at 7.1mph in Westminster and in Camden, the report said.

In his written answer to Garratt, Khan continued: “Lowering speeds is one of the most important things that can be done to make our streets safer.

“Over half of London’s roads now have a 20mph speed limit and London’s boroughs continue to lead the way with 19 of the 33 boroughs now having 20mph speed limits across their roads.

“In 2020, we reduced the speed limit on all TfL roads within the central London Congestion Charge zone to 20mph, with preliminary data showing a 24.9% reduction in fatal and serious injuries post implementation.”

On the question of whether average bus speeds are being impacted, the mayor added: “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.”

In a pledge to speed up the capital’s buses, the mayor said: “I fully recognise the importance and scale of the challenge involved in improving bus journey times and reliability.

“That is why TfL is working in partnership with bus operators and their borough colleagues to deliver a programme of technological, operational and policy improvements to better support bus performance while also delivering my Vision Zero ambition.”

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