When a pedestrian is hit by a car, people usually find fault in individuals. They ask, “was the driver careless, or was the pedestrian jaywalking?” But if you zoom out and see that collisions keep happening in the same place, again and again, then it starts to look less like a problem with individuals and more like a problem with the road. Humans are bound to make mistakes, but roads can be redesigned to reduce the likelihood that mistakes lead to death. That is the philosophy behind traffic calming.
Modern traffic calming supposedly originated in the city of Delft in the Netherlands in the 1960s, when a group of local residents got so frustrated with cars speeding dangerously through their neighbourhood that they ripped up paving stones in the middle of the night, leaving behind an s-shaped path so that cars were forced to slow down. By the 1970s, this had evolved into a concept called “woonerven” (living yards) supported by the city government. Residential streets were transformed into community front yards. They were not car-free, but cars had to give pedestrians priority. Once drivers were forced to carefully weave their way around benches, bike racks, trees, and even children’s playground equipment, those streets ceased to be attractive shortcuts, and the number of traffic-related injuries actually decreased by 50%.
This innovation unlocked an important insight, which is that making drivers uncomfortable makes pedestrians safer. When placed on a narrow and visually complex street, people drive more cautiously. Conversely, when offered a wide road free of obstacles, they feel safe going faster, and consequently pay less attention. This was a major departure from the conventional wisdom at the time, which emphasized maximizing traffic flow by widening roads and getting pedestrians out of the way of vehicles. Over time, traffic engineers have devised an whole bag of tricks to manipulate drivers into slowing down and paying attention.
A Dutch “woonerf” residential street. Source: Erauch, CC BY_SA 3.0, Wikimedia Commons.
Traffic calming was introduced on Hong Kong’s streets in the early 2000s to improve safety in overcrowded shopping districts like Causeway Bay, Mong Kok and Tsim Sha Tsui, where pedestrians were spilling off narrow pavements into the road. Only a handful of streets were fully pedestrianised, but others nearby received traffic calming interventions. These were nowhere near as dramatic as Dutch woonerven, but they operate from similar principles. You have probably walked past them a thousand times without noticing, so here are some of the low key design interventions that make streets safer.
At junctions without traffic lights, kerb build-outs serve an important function. They widen the pavement at pedestrian crossings to reduce the distance to cross the road. By extending the pavement slightly beyond the row of parked cars, they allow pedestrians and cars to see each other more easily. Kerb build-outs also encourage drivers to slow down by narrowing the roadway and reducing the corner radius.
People usually drive faster on wide roads than narrow ones. A narrower roadway reduces the perceived tolerance for error, and brings more objects into the centre of the driver’s visual field, which increases their awareness of their own speed and prompts them to pay closer attention. Smaller corner radii (i.e. tighter turns) also force drivers to slow down.
Kerb build-outs reduce crossing distances for pedestrians and ensure that parked cars do not obstruct their view of traffic. Photo credit: City Unseen, 2024.
Seconds after the taxi stopped to avoid hitting the cardboard collector, the black car turned into her path. On this leg of the junction of Boundary Street and Lai Chi Kok Road, pedestrians still have to cross three lanes of traffic despite kerb build-outs. Kerb build-outs are best used where the road can be narrowed to two lanes, or even a single lane. Photo credit: City Unseen, 2024
Chicane on Lock Road, Tsim Sha Tsui. Photo credit: City Unseen, 2024.
Chicanes take a straight road and introduce kerb extensions, parking spaces, or planting beds on alternating sides, creating a serpentine route like the residents of Delft did decades ago. You can think of them as the horizontal equivalent of a speed bump. A study by the UK Transport Research Laboratory in 1998 found that one-way chicanes reduced traffic speeds by about 20 km/h (12 mph), and two-way chicanes reduced speeds by about 10 km/h (6 mph).
Left: Raised table at the corner of Fuk Wing Street and Kweilin Street, Sham Shui Po. Right: Edge of the raised table. Vehicles have to go up a small ramp, while pedestrians can cross at the same level. Photo credits: City Unseen, 2024.
You may have noticed that certain junctions are slightly raised and surfaced with red asphalt or brick. What purpose does this serve?
This is a raised table, which is essentially a very large, flat speed hump. They slow vehicles down where pedestrians cross the road, and their raised surface allows pedestrians to cross at the same flat level. This makes it easier for people with wheelchairs, prams, luggage or trolleys.
The red surface also tells drivers this space is different from a normal road. If it is the same colour as the surrounding pavement, it looks like an extension of the pedestrian space, which alerts them to pay attention to people crossing.
Modal filter at Hankow Road and Peking Road, Tsim Sha Tsui. Photo credit: City Unseen, 2024.
At the junction of Hankow Road and Peking Road in Tsim Sha Tsui, the pavement does a curious thing, stretching diagonally from one corner to the opposite corner. There are bollards on either side to protect the pedestrians and prevent cars from driving straight through. Drivers can only turn left. This is called a modal filter, when permeable barriers are used to restrict access to certain modes of transport (i.e. cars), while allowing others (i.e. pedestrians and cyclists) through.
Modal filters are used to create a lower-traffic, more pedestrian-friendly environment by disconnecting minor streets from major roads, or preventing drivers from using a street as a shortcut. People who wish to drive to these destinations can still do so, but need to take a less direct route.
It is obvious that the faster a car is going, the more likely it is to kill a pedestrian in a collision. However, there has been extensive research into quantifying exactly how likely you are to die when hit by vehicles going at different speeds. Studies from different countries have come up with somewhat different numbers (the chart below is based on a recent meta-analysis of 20 studies), but they generally agree that the risk of death rises sharply when cars travel faster than 30 km/h.
If a car hits you at 30 km/h, you have a 5% chance of dying. This increases to 12% at 40 km/h, 29% at 50 km/h, and 53% at 60 km/h. If you are hit at highway speeds (80 km/h), you have a 90% chance of dying.
Risk of death in vehicle-pedestrian collisions at different impact speeds. Graphic by City Unseen based on Qinaat Hussain et al., 2019.
These findings have generated a worldwide trend of establishing low speed limit zones. In recent years, Shanghai, the Netherlands, and Spain have adopted 30 km/h speed limits on minor roads. London has a 20 mph (32 km/h) limit on 60% of its urban roads, and Singapore has implemented “silver zones” with a 40 km/h speed limit in areas with a high elderly population.
Until very recently, Hong Kong had a blanket 50 km/h speed limit in all urban areas, the product of an outdated 1980s Transport Planning and Design Manual. In 2020, the Transport Department began trialling 30 km/h zones in parts of Sham Shui Po, Kowloon City, Yuen Long, Sha Tin, and Shau Kei Wan, and Prince Edward, most of them near schools and on market streets. Low speed zones are best used in combination with other traffic calming measures, as drivers often ignore legal limits.
Low speed zones on Ki Lung Street (left) and Tong Yam Street (right), Sham Shui Po. Photo credit: City Unseen, 2024.
Right now, you may be thinking that the traffic calming measures shown above are suitable for minor streets, what about main roads? Aren’t those even more dangerous for pedestrians? That is a reasonable guess, but it is not supported by the data. In 2020, traffic safety and urban design advocacy group Street Reset analysed 5 years of traffic collision data between 2015 and 2019, and identified ten hot zones with the highest rate of pedestrian collisions per kilometre of road. Only two of these zones included main roads—the junction of Jordan Road with Shanghai Street, and Nathan Road with Dundas Street. The rest were on minor (secondary) roads, and four were located near wet markets.
The reason for this might be because main roads have traffic light controlled pedestrian crossings, but many minor streets do not. Yet many minor streets carry both heavy pedestrian and vehicular traffic. Pavements might be too narrow, forcing people to walk in the road, which the government often tries to address by installing railings. However, railings create their own risks when people sneak through the gaps, then become trapped on the outside. Many minor streets have wide vehicle lanes (3.65m is standard), which encourages people to drive faster.
The most dangerous stretch of road identified was Wan Chai Road between Burrows Street and Heard Street, which not only had the highest rate of pedestrian collisions per km, but the highest rate of serious injuries (43% of collisions resulted in serious injury, compared to a territory-wide average of 23%). It is a busy bus route with narrow pavements and no pedestrian crossings at the junctions with Mallory Street or Heard Street, leaving pedestrians to make long detours or to risk crossing two or three lanes of bidirectional traffic.
This section of Wan Chai Road had the highest rate of pedestrian collisions per km in Hong Kong from 2015-2019. The blue sign on the far side of the road reads “please do not cross here”. Photo credit: City Unseen, 2024.
In other words, minor streets are where traffic calming is most needed, and where it would be most beneficial. So far, these measures have been installed in major commercial districts, touristy areas, and near public transport hubs and school zones, but there are still many areas where it is missing. Next time you are walking around, try to identify any traffic calming features that you see. Notice how they affect your walking experience. And then notice the streets that feel less safe where traffic calming features are absent.
This article was written in collaboration with Street Reset. Check them out on Instagram and Facebook.
Street Reset, “Position Paper for the Future Traffic and Transport Strategy”, November 2023.
Street Reset, “Collision Not Accident – An Overview of Road Danger Against Pedestrians in Hong Kong”, August 2022.
Federal Highway Administration, “FHWA Case Studv No. 19: The History and Development of Traffic Calming”, Government of the United States, 1994.
Mike Lydon and Anthony Garcia, “Woonerfs were tactical urbanism before there was ‘tactical urbanism’”, Greater Greater Washington, 15 April 2015.
Qinaat Hussein et al., “The relationship between impact speed and the probability of pedestrian fatality during a vehicle-pedestrian crash: A systematic review and metaanalysis”, Accident Analysis and Prevention, vol. 129, 2019, pp. 241-249.
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