On the Roads


A HKU team used machine learning to study hundreds of bus dashcams and found pedestrians uniquely vulnerable to bus crashes (image: Accident Analysis & Protection)

More railings would prevent injuries from bus crashes: that’s the key recommendation from a Hong Kong University research team who studied thousands of Hong Kong bus dashcam videos for clues on pedestrian behaviour.

The study, published in June 2023 edition of Accident Analysis & Prevention and led by the university’s Head of Geography Professor Becky Loo, wanted to look away from traditional crash causes such as bus driver fatigue and driving skill and instead study risks from the street environment.

Using machine learning models, researchers studied nine months of dashcams from 33 local bus routes, matching them to crash location data from Transport Department to assess five risk factors which they say are “rarely captured” in previous studies. Those include railing density, pedestrian density, overcrowding at bus stops and so-called “jaywalking”, an outdated term still used in some countries to describe people walking in on a public road where motor vehicles are presumed to be the dominant mode of transport.

The study finds locations with pedestrian railings have seen fewer serious bus crashes and recommend that the removal of railings put forward by walkability initiatives “should be reconsidered in dense urban areas where other traffic calming initiatives are not feasible to install”.

“Although pedestrian railing hinders the vibrancy of some streets, results here suggest that it is still necessary to adopt railing as a protection against serious bus crashes,” the researchers say.

Researchers also find bus stop design to be critical, with Hong Kong bus stops tending to see more slight crashes.

“This result suggests better design considerations at bus stops are needed so that bus passengers can have a safer environment to wait for buses on the one hand, and to get on and off buses in an orderly manner on the other hand,” say the authors.

Loo has been approached for comment on whether illegal parking at bus stops was a consideration in “design”, with many bus stops across the city consistently blocked by illegally parked cars or trucks and requiring passengers to board or alight from a busy road.

The study also finds a difference between bus crashes and other road crashes, with pedestrian crowding and the railing density more critical in predicting bus crashes than crashes involving other types of vehicle. Researchers recommend advanced transport planning could target different vehicle categories to better manage road safety.

The high prevalence of pedestrian railings in Hong Kong has been a bone of contention between walkability campaigners and the government for some years. The government had promised to review railing locations after 2019 when over 60 km of roadside railings were removed by protestors or the police. Yet almost all railings have been restored, at cost of around $15 million, while no study or consultation on their replacement has taken place. Last year the government said it had replaced some railings with “a new type of bollards [sic]” on around 900 metres of road in Causeway Bay under a pilot scheme “to enhance the walking environment and streetscape”. Most of the new-style bollards are connected by chains, while some are freestanding and allow pedestrian movement across their line.

Lead researcher Becky Loo shared the paper on LinkedIn just hours after a serious bus crash in Cheung Sha Wan saw 41 passengers injured as a double-decker smashed into an off-ramp divider and almost overturned.



Leave a Reply