Cyclists’ hi-vis clothing invisible to some car brands’ automated emergency braking systems, shocking crash prevention study finds

During the winter months, police forces, politicians, and road safety organisations regularly advise cyclists and pedestrians to ‘be safe, be seen’ by wearing reflective clothing when out on the roads. But, according to an alarming new study conducted by a vehicle safety organisation, hi-vis gear could in fact make cyclists invisible to some car brands’ automated emergency braking systems.

The research, carried out by the US-based Insurance Institute for Highway Safety (IIHS), even found that the crash prevention system employed in a Honda CR-V failed to recognise or slow down even a fraction for pedestrians wearing reflective clothing, while the braking system deployed in a Mazda CX-5 failed to stop for a mannequin wearing clothes with reflective strips.

According to the IIHS, past research has shown that automatic emergency braking (AEB) systems reduce the rate of pedestrian crashes of all severities by 27 per cent. However, on dark roads at night, their effect becomes negligible.

The institute’s new study sought out to test the effects of “conspicuous clothing” and increased road lighting at night on the performance of AEB systems installed in three 2023 car models, a Honda CR-V, Mazda CX-5, and Subaru Forester.

Researchers conducted multiple trials with an adult-sized dummy wearing a range of different clothes: a black jumper and trousers (top right in the above image), a highly reflective jacket with black trousers (bottom right), a black jumper and trousers with reflective strips attached to the dummy’s limbs and joints (bottom left), and a white jumper and trousers (top left).

The tests were run at 25mph in three conditions: with no road lighting, with 10 lux of illumination, and with 20 lux of illumination (recommended by the US government) on the pavement, with the dummy crossing the road in front of the vehicle in all scenarios.

During every test, regardless of the lighting conditions, both the Honda CR-V and the Mazda CX-5 hit the dummy wearing the reflective strips without slowing down at all.

Meanwhile, the Honda also hit the dummy wearing the reflective jacket without slowing every time, in every type of lighting condition.

The unfortunate outcome for the dummy wearing reflective stripes

Interestingly, the Honda performed better when the dummy was wearing black or white clothing. For the dummy wearing black clothes it slowed slightly with 10 lux of illumination, and by 39 per cent with 20 lux. It almost came to a complete stop for white clothes and 10 lux of lighting, and slowed by 62 per cent in 20 lux.

The Mazda, meanwhile, slowed by roughly half in all types of lighting for the dummy in the reflective jacket, and by around a third in most types of lighting when confronted with both black and white clothing – though its AEB system performed best for black clothing in 20 lux of illumination, slowing by 84 per cent.

More encouragingly, the Subaru Forester came to a complete stop and avoided a collision in every single test bar one – where it slowed by only 82 per cent when heading towards the dummy wearing reflective strips in 10 lux of illumination.

“The placement and motion of reflective strips on the joints and limbs of pants and jackets allows drivers to quickly recognise the pattern of movement as a person,” the study’s author, David Kidd, a senior research scientist at IIHS, said after publishing the results.

“Unfortunately, the moving strips didn’t have the same effect for the pedestrian AEB systems we tested and probably confounded their sensors.”

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According to Kidd, it’s not clear why the Honda and Mazda systems struggled with the reflective strips or how many other systems might have trouble identifying pedestrians and cyclists wearing this type of clothing, a lapse he described as a “concern” considering the rhetoric around wearing hi-vis clothing.

“It certainly was surprising that those two vehicles didn’t respond at all when the pedestrian was wearing those reflective strips on the joints and limbs,” he said. “That’s a configuration that you have emergency personnel as well as construction workers use to become very visible to drivers at night.

“The Forester responded without any problems, so it can be done. Hopefully bringing these results to light motivates manufacturers to improve the technology so that it can respond to pedestrians no matter what they’re wearing.

“This technology, automatic emergency braking, is amazing and it does prevent crashes, but it’s still nascent technology that’s not going to respond to everything.”

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“These results suggest that some automakers need to tweak their pedestrian automatic emergency braking systems,” IIHS President David Harkey added.

“It’s untenable that the clothes that pedestrians, cyclists, and roadway workers wear to be safe may make them harder for crash avoidance technology to recognise.

“This is a worrisome blind spot. To make good on their potential, pedestrian detection systems have to work with the other commonly used safety measures.”

In response to the researchers’ findings, Maza spokesperson Tamara Mlynarczyk said: “Roadway safety for everyone, including those in and around our vehicles, is a top priority for Mazda.

“Our engineers are continuously working to improve Mazda’s crash avoidance systems and are already using these latest IIHS results to further assist us in this work, with special consideration for nighttime pedestrian scenarios.”

Meanwhile, Honda said in a statement: “Continuous improvement is a core part of the company’s vehicle development process, and we will closely analyse the results of IIHS’ recent non-standard pedestrian AEB testing in an effort to enhance future model performance.”

> Police ask pedestrians to wear hi-vis following spate of road deaths in Scotland

As noted above, campaigns advising cyclists and pedestrians to wear hi-vis, reflective clothing are a common sight in the UK, but have sometimes come in for criticism from those who claim they place the onus for road safety on the most vulnerable users.

In February 2023, Police Scotland found itself at the centre of a “victim blaming” row after a chief inspector urged pedestrians to wear “reflective or fluorescent” clothing after six people walking were killed after being hit by other road users in the space of just 13 days.

Ch Insp Lorraine Napier argued that in light of the incidents, officers should encourage all road users to keep safe, first asking pedestrians to stay visible.

“Pedestrians are considered vulnerable road users and, in winter, particularly when it is dark, pedestrians should wear reflective or fluorescent clothing,” she said.

“I would also urge pedestrians to be mindful of their surroundings and to ensure they are not putting themselves at risk.”