Mayor of London: 20-mph zones save lives and don’t slow down traffic

The Mayor of London, Sadiq Khan, wrote in the British newspaper The Guardian about why introducing 20-mph zones is important for all residents. Here are his key arguments.

“There’s been far too much empty talk and hypocrisy around this issue. Ordinary people just want safe streets for themselves and their loved ones — and that’s something we can achieve,” writes the Mayor.

“Every 17 minutes. That’s how often someone in the UK is killed or seriously injured in a traffic collision. Each of these tragedies represents an unimaginable loss — for those left behind, and for survivors whose injuries may change their lives forever. Last year alone, road traffic crashes claimed more than 1,600 lives. Yet we have the power to prevent them.

Take speed limits, for example. Research published by Transport for London shows that the number of people killed or seriously injured on roads in London’s boroughs fell by 34% after the introduction of a 20-mph (about 32 km/h) speed limit. The number of children killed dropped by an even more dramatic 75% (from four to one). At the same time, drivers’ fears have proven unfounded. Despite critics’ claims, the 20-mph limit has not slowed traffic, since journey times are mostly determined by delays at junctions — not by the actual driving speed.”

Slowing down saves lives

Roads with a 20-mph limit aren’t just safer — they’re also quieter, encouraging more people to walk or cycle. Those who still drive benefit too: they experience fewer crashes and lower insurance costs. It’s no surprise that a majority of residents support slower limits in their neighbourhoods — more than three out of four people believe that 20 mph is the right choice.

Our experience isn’t unique. In Wales, during the first year after introducing a 20-mph speed limit, there were 100 fewer people killed or seriously injured. As Mayor of the capital, I’ve never approached road safety from an ideological standpoint or based on beliefs or prejudice — but on evidence and what works best. If we want to save lives, the data is clear: there’s no time to waste.

That’s why we’re introducing 20-mph limits on appropriate roads. Thanks to our policies, half of London’s streets now have this lower speed limit. We’ve created more than 800 “school streets” across the city, reduced toxic air pollution, and made it safer and healthier for thousands of children to travel to school. At the same time, we’ve quintupled the number of protected cycle lanes, giving more Londoners the confidence to swap four wheels for two.

Fewer emissions, fewer deaths

Step by step, street by street, we’ve made the capital a better place to walk, cycle, and drive. Faced with complex challenges, we’ve had the courage to find our own solutions — even when the rest of the world had none. When I launched the Ultra Low Emission Zone (ULEZ), it was the first of its kind in the world. Other cities have since followed with similar plans, but London’s remains the largest in the world.

In 2024, a year after its expansion, nitrogen oxide levels — toxic gases that worsen asthma and increase the risk of lung cancer — fell by 27% along major roads. Since the system was introduced in 2019, air quality has improved at 99% of monitoring stations across the capital. In a city where air pollution is linked to up to 4,000 premature deaths a year, ULEZ is saving lives.

But it’s not just about ULEZ. We knew that lorries are five times more likely to be involved in a fatal collision than their share of traffic would suggest. That’s why, in 2021, we became the first in the world to introduce a Direct Vision Standard for heavy goods vehicles — forcing tens of thousands of dangerous trucks to adopt safety measures and improve driver visibility. The policy is working. By 2023, the number of vulnerable road users killed in collisions with lorries had fallen by 62% compared to the 2017–2019 average. Meanwhile, the European Union has introduced similar measures expected to save thousands of lives across Europe.

Vision Zero

When it comes to improving road safety, our capital has achieved results that are unprecedented anywhere else. But the truth is that despite this impressive progress, too many places still have speed limits that endanger pedestrians. We can — and must — do more, because none of the tragedies that occur on London’s streets are inevitable.

This core belief — that even one death on our roads is one too many — is at the heart of my Vision Zero for London. The goal of this strategy is to eliminate all deaths and serious injuries from our transport network by 2041. But we can only succeed if every borough plays its part.

Most London boroughs have seized the opportunity to make their streets safer: 21 boroughs now have a default speed limit of 20 mph (around 32 km/h). Unfortunately, a handful of boroughs refuse to cooperate. In these “blocking boroughs,” local leaders have resisted lower speed limits on their streets. To them, my message is clear: it’s time to stop slowing progress. Playing political games with speed limits achieves nothing — except more injuries and lost lives.

Every day, I meet people who tell me they want to keep fighting for cleaner air and safer, slower streets. Some are activists who have dedicated their lives to making transport safer and more sustainable.

But most are ordinary people:

• children walking home from school,
• parents cycling to work,
• carers on their way to loved ones.

What they want is simple: the chance to live their everyday lives knowing they are safe.

For them, the fight for safer streets must go on.

More Safety for Prague, Too

Improving the safety of the most vulnerable road users is also the goal of Výzva 0 — an initiative led by AutoMat and the independent group Iniciativa 0. The movement formed organically in response to the death of a young cyclist in Prague 10, who was killed by a truck.

The aim of Challenge 0 is to urge politicians and authorities not to delay and not to ignore the need for safe infrastructure for pedestrians and people on bicycles.

Inspired by Sweden’s Vision Zero, the Czech initiative shares the same ambition: to achieve zero traffic fatalities in the city.

Join the movement — and let’s push institutions to take real action together.