Reducing speed limits: The next big move for road safety
Matthew Beedham·Sep 14, 2021

Reducing speed limits: The next big move for road safety

Matthew Beedham
Sep 14, 2021 · 5 min read
Reducing speed limits: The next big move for road safety | TomTom Newsroom

In the past month, Paris’ Mayor Anne Hidalgo gave the go-ahead to completely reduce the city’s speed limit from 50 kph (31 mph) to 30 kph (18 mph). With most Parisians in favor of the change, it suggests that speed limit reductions could be the next transport policy to sweep the world’s roads.

Hidalgo’s goal is to reduce pollution and improve safety. However, there’s been some opposition. Most critics claim traffic jams will worsen, pollution will increase and the whole thing will make everyone’s lives more stressful. Interestingly, the majority of those that live in the city support these measures. Outside the city, the majority tend to be against reducing speed limits.

For Paris, this won’t be the last change to its infrastructure. As the next hosts of the Olympic games, Hidalgo is on a path to making Paris cleaner and greener as it readies itself for the world stage. Most cars are expected to be banned entirely from the city center next year, car parking space is being removed and segregated bike lanes are springing up across the city’s arrondissements.

There will likely be greater division as Hidalgo continues restructuring how Paris’ residents move around the city, but the benefits will far outweigh the negatives.

There are only upsides to speed limit reductions

Research has long confirmed the benefits of reducing speed limits in urban areas. It reduces noise, pollution, the rate and severity of accidents, and cuts fuel consumption.

In a world where we’re constantly under pressure to be places on time, a 20 kph (13 mph) reduction in speed limit admittedly sounds like it’ll create more problems than it will solve. However, changes to infrastructure often show to have different outcomes to what we’d first assume. Building more roads does not reduce congestion and taking space away from cars for cycle lanes does not increase congestion, for example.

Reducing speed limits has shown to have, overall, little impact on point-to-point travel times across cities. In cities, lowered speed limits only affect those rare and fleeting moments on longer stretches of road when we might be able to hit the speed limit. These moments are so few and far between, that lower speed limits have little impact on overall travel times in busy cities.

What’s more, according to data from Thomson Reuters, the average speed traveled across Paris between 7am and 9pm each day is around 15 kph (9.5 mph). In fact, the average speed has been declining steadily for the past 20 years. NO2 and PM10 particulate pollution levels have been declining too.

While average speeds will be largely unaffected, the 20 kph (13 mph) decrease in speed limit should have a pronounced impact on road safety.

According to clean transport campaign group, Transport and Environment, when speed limits are reduced from 50 kph to 30 kph the overall number of accidents decreases by 20%.

The severity of accidents is reduced even more. Figures from Belgium suggest that 45% of pedestrians hit by cars traveling at 50 kph die, however that number drops to 5% when the car is only traveling 30 kph.

When speed limits were cut from 50 to 30 kph in Munster, Germany the number of people severely injured in road accidents dropped by 72%. Regardless of the city, that 20 kph drop is crucial to safety.

When it comes to noise pollution, a 30 kph speed limit reduces noise by 3 decibels – that’s a 50% reduction in overall noise levels.

The impact of speed limit reductions cannot be underestimated. Many major cities, such as Berlin, London, New York, Dublin and Brussels already have speed limits of under 50 kph. The outcomes are showing to be nothing but positive.

However, there are still plenty of cities, like those in Portugal, Spain, Italy and Poland, that should follow suit. On motorways, it’s the same story.

Next up, Germany’s Autobahns

Outside of cities, speed limits on motorways, highways, interstates and autobahns are now coming under scrutiny.

Germany’s derestricted Autobahns could be finally getting a universal speed limit. Around three quarters of Germany’s Autobahns don’t have a speed limit at the time of writing, but proposals are in place to apply a 130 kph limit across the country’s intercity roads.

While Paris witnessed some opposition, discussing speed limits on Germany’s delimited Autobahns is almost a no-go. But as with what we see in cities, the impact on pollution and safety is only positive.

While overall road safety in Germany is quite good, the Autobahns are a different story. According to Organization for Economic Cooperation and Development (OECD) and the German Road Safety Council, the fatality rate over each 1,000 km section of Autobahn is 30.2% – the European average is 26.4%.

What’s more, per billion kilometers traveled on motorways, fatality rates in Germany (1.6) are twice what they are in the UK (0.8).

When it comes to pollution, Germany’s environment agency calculates that a 130 kph speed limit across its highway network would save more than two million tons of CO2 a year – based on current vehicle ownership.

Speed limits: The obvious choice

Whether in the city or the highway, more considered speed limits seem like the simple answer to improving road safety and the environment – the only real hurdle is politics.

When implementing them requires nothing more than some new signage, it’s one of the technologically easiest ways of improving safety and reducing emissions.

The evidence is powerful, outcomes are positive and there is seemingly no downside to reducing speed limits. Tighter speed limits in cities and more considered limits on highways are an absolute must if we’re to improve road safety and reach carbon emission goals.

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