The safety tech on your lorry (and the one behind it) might not be as good as you think

Just after 2:30am, on an unlit stretch of motorway, doing 50mph, an unlit cyclist in dark clothing appeared in the middle of a live lane directly ahead. No lights, no reflective material, moving at a normal cycling pace. The vehicle's autonomous emergency braking system did not detect them. A manual, emergency lane change was the only reason it didn't end in a collision — and it very nearly didn't happen at all, because on a motorway, at that hour, a cyclist is the last thing a driver is scanning for.

It would be easy to read the AEB's silence as a fault — a system that should have worked and didn't. It's worth being precise about why that's not quite right, because the real explanation is more useful than the reassurance, and it says something every HGV driver and operator should understand about what AEB is actually built to do.

The speed alone put it outside the system's scope

Start with the simplest explanation, because it's the one that applies regardless of the vehicle, its age, or which manufacturer built it. The pedestrian/cyclist-braking function of HGV AEB has a regulatory operating ceiling: UN Regulation 131/152 requires it to be active "at least between 20 km/h and 60 km/h" (roughly 12–37mph). Mercedes-Benz's own marketing for its newest system, Active Brake Assist 6 Plus, uses the same figure — reacting to pedestrians and cyclists "up to 60 km/h."

At 50mph — around 80 km/h — a lorry is already travelling well above that ceiling. This isn't a case of a system failing to spot someone it was supposed to catch. For the pedestrian/cyclist function specifically, current AEB isn't designed, tested, or required to intervene at motorway cruising speed at all. Vehicle-to-vehicle collision braking operates at much higher speeds, but the person-detection function is deliberately capped low — almost certainly because a full braking intervention for a person in the road isn't considered safely achievable or reliable once closing speeds get that high.

And there's a reason the ceiling sits where it does. Cyclists aren't legally permitted on the motorway — the Highway Code and the Motorways Traffic Regulations restrict the carriageway to motor vehicles, bar rare authorised exceptions. So when manufacturers calibrate pedestrian/cyclist AEB to the 20–60 km/h band, they're not cutting a corner. They're building for the realistic scenario: a cyclist crossing a road at urban or rural speeds, not a live motorway lane at 50–60mph where a cyclist legally shouldn't be in the first place.

Which is exactly what makes the rare occasions it does happen so dangerous. It's a double gap, not one. The technology isn't built to cover that scenario, and the driver isn't primed for it either — on a motorway you're scanning for stalled vehicles, debris, and other traffic, not a cyclist, because the entire road is designed on the assumption they won't be there.

Darkness makes an already limited system worse

Layer the time of day on top of that, and the picture gets worse still. AEB effectiveness at night is substantially reduced compared to daylight, across every study that's tested it properly. Research from the Insurance Institute for Highway Safety found that while AEB with pedestrian detection reduces pedestrian crash rates by around a quarter in good conditions, that effect becomes negligible on genuinely dark roads. Academic modelling of AEB effectiveness for vulnerable road users found darkness had a bigger negative impact on pedestrian detection specifically than on cyclist detection — but the underlying point holds across both: low light is the condition where these systems are least able to do their job, which is precisely the condition in which most fatal pedestrian and cyclist collisions actually happen. Estimates suggest around 70% of pedestrian fatalities occur at night or in poor lighting — the exact scenario where current detection technology is weakest.

There's a further wrinkle worth knowing, because it genuinely surprises people: testing has found that some systems struggle even with a pedestrian wearing high-visibility or reflective clothing at night, in certain lighting conditions — the very clothing designed to make a person visible to a human driver can, in some systems, be harder for a camera-based detection algorithm to interpret correctly than plain clothing. Nothing about hi-vis is a guaranteed fix for how a detection system reads the road — and in this case, there wasn't any hi-vis or reflective material to begin with.

What the regulations require — and where manufacturers are starting to go further

Under the current legal minimum, an HGV's AEB system only has to detect a single pedestrian crossing directly in front of the vehicle, and even that within the 20–60 km/h band above. It does not have to detect cyclists, and it does not have to detect groups of pedestrians. When the updated standard was being agreed, manufacturers said cyclist-detecting AEB for lorries wasn't yet available at all.

That's shifting, and it's worth being fair to where the technology has actually got to. Volvo's next-generation Emergency Brake system, which detects cyclists as well as pedestrians, became standard equipment in Europe on all new FH, FM and FMX trucks from 2025 — ahead of what regulation currently requires. Mercedes-Benz's Active Brake Assist 6 Plus, adding the same cyclist-detection capability, is rolling out from early 2026. Scania's L-series has been recognised by Euro NCAP specifically for its pedestrian and cyclist protection systems. So cyclist-aware AEB is a real, current feature from several major manufacturers — it just isn't universal yet, rollout is staggered by model and build date, and none of it is marketed or tested as reliable against an unlit, unreflective cyclist at night, at any speed.

Put together, a brand-new HGV missing an unlit cyclist on a dark motorway at 50mph isn't evidence that something has gone wrong with the vehicle. It's the combined, entirely explicable result of a system with a legal speed ceiling built for legal road conditions, degraded further by darkness, encountering a hazard — a cyclist on a motorway, at night, with no lights — that falls outside almost every assumption the system, and the driver, were reasonably working from.

It cuts both ways — car AEB has the same blind spot for the back of your trailer

It would be easy to read all of this as a problem with HGV technology specifically. It isn't. The same limitation runs in the other direction too, and if anything the evidence there is even starker.

Euro NCAP published research earlier this year — DVSA highlighted it at the Invergold Transport Conference 2026 as part of their own push to reduce rear-end impacts on lorries — testing how well car AEB systems recognise the back of a lorry. Every system tested caught a standard laboratory test target without fail. But tested against real HGV rear-ends — curtainside and skeletal trailers, and the impact protection vehicles (IPVs) used at roadworks — the detection rate fell in several cases, regardless of body style. There's a generational divide too: the newest ADAS, combining camera and radar, performs noticeably better than older systems. But with the average age of cars on UK and EU roads, Euro NCAP estimates it will take more than 15 years before most cars on the road are reliably able to avoid a stationary trailer. Rear and trailer underrun impacts are already estimated to cost around 400 lives a year across the EU and UK.

Put the two findings side by side and the pattern is consistent rather than coincidental. Whether it's an HGV failing to spot a cyclist or a car failing to spot the back of a trailer, the technology performs impressively in the conditions it was tested and marketed for, and considerably less reliably outside them. The amazing tech is real. It's the assumption that it fills every gap that isn't.

And when a car does hit — the underrun guard often doesn't hold

The same research, also covered at the Invergold Transport Conference 2026, went a step further, and this part is specifically UK-relevant: the testing was prompted by UK National Highways, working with Germany's ADAC, Swedish authorities and the US's IIHS, not run as a purely European exercise.

Euro NCAP crash-tested trailers meeting the mandatory rear underrun protection standard that applies here — UN ECE Regulation 58.03 — at 56 km/h (35mph), the kind of speed a car might realistically still be doing in an unavoidable rear-end collision. At a 30% offset, a Schmitz Cargobull trailer's underrun guard failed to stop the test car passing underneath it: the structure penetrated the passenger compartment and caused fatal head and neck injuries to the test dummy. At a higher, roughly 75% overlap, a Krone trailer's underrun bar broke away entirely, and the car went on to strike the rear axle, again destroying the occupant compartment. Both trailers met the mandatory standard.

The same test run against a guard built to the voluntary US IIHS TOUGHGUARD standard produced a completely different outcome: the guard stayed intact, and the car's own crash structure, airbags and restraints were able to work as they were designed to. Euro NCAP's conclusion was blunt — the current mandatory European standard is not fit for purpose, and manufacturers were called on to improve rear underrun protection voluntarily, ahead of any change to the regulation itself.

So the reassurance that "our rear underrun protection meets the standard" is true, and currently not worth very much. It's the same lesson as the detection findings, from the other end of the same collision: meeting the legal minimum and actually surviving the impact are not, on this evidence, the same thing.

What this actually means for a driver and an operator

None of this is a reason to distrust AEB, and it's certainly not a reason to remove it from the safety case for fitting it. It genuinely reduces certain categories of collision, and mitigation — even a partial speed reduction before impact — saves lives in a meaningful proportion of the incidents it does catch. The point is narrower and more practical: AEB is a last line of defence with a known, published, limited scope — capped by speed as well as by what it's looking for — not a guarantee that anything in the road will be detected and stopped for. Manufacturer literature and independent safety researchers say this consistently: these are backup systems, built to catch what a driver misses, not systems a driver should ever rely on to catch what they haven't seen themselves.

For an operator, that has a few practical consequences worth building into training and induction rather than leaving as an assumption. Drivers should understand specifically what their fleet's AEB does and doesn't cover — the speed ceiling on pedestrian/cyclist detection is as important to know as the cyclist gap itself, because it means the system offers essentially no back-up at all once you're at motorway cruising speed. Route risk assessment for unlit or poorly lit sections should factor in that this is where both human and system detection are weakest simultaneously, not just where a driver needs to concentrate harder. And any driver debrief following a near-miss involving a vulnerable road user is a genuine opportunity to reinforce, with a real example, exactly what the technology in the cab is and isn't watching for — including the reminder that a hazard being rare and unexpected is precisely when it's most dangerous, not least.

The rear underrun findings point the same lesson in a different direction: don't assume the car behind will stop just because it has AEB, and don't assume the mandatory rear underrun guard will hold if it doesn't. Rear conspicuity — clean, unobstructed rear markers and reflective plates, and correctly positioned hazard/warning triangles if you're stopped on the hard shoulder or verge — matters more, not less, once you know a well-specified car with modern ADAS still isn't guaranteed to recognise your trailer in time. And when specifying or replacing trailers, it's worth asking what rear underrun protection is actually fitted beyond the legal minimum, given what Euro NCAP's testing found that minimum currently delivers.

Where this sits in your compliance system

This doesn't map onto a single line item in the audit framework the way a defect or a licensing gap would — it's closer to a driver training and risk-awareness question that cuts across several areas: additional safety equipment and its correct use, driver training and CPD content, route and scheduling risk assessment, and vehicle standards where rear marking and underrun protection are concerned. What we're really looking for on audit is whether an operator's drivers have been told, specifically and honestly, what their AEB actually covers — not left to assume it's a safety net for every road user in every condition, because for an unlit cyclist on a motorway at night, at normal cruising speed, in a great many HGVs on the road today, it simply isn't one. And on the flip side, whether rear conspicuity is being treated as the genuine, ongoing safeguard it is, not a tick-box exercise made redundant by whatever's fitted in the car behind — and whether, when trailers are next specified or replaced, the legal minimum on rear underrun protection is treated as a floor worth exceeding rather than a box already ticked.

If you'd like your driver training and vehicle technology briefing reviewed as part of a full compliance audit, that's exactly what we do. Get in touch at enquiries@ukfleetaudit.co.uk.

References

European Transport Safety Council (2019) ETSC welcomes higher standards for automated emergency braking systems on HGVs. Available at: https://etsc.eu/etsc-welcomes-higher-standards-for-automated-emergency-braking-systems-on-hgvs/ (Accessed: 21 September 2026).

InterRegs (2024) Updates to UN ECE Regulation on Advanced Emergency Braking Systems for Heavy Vehicles Published. Available at: https://www.interregs.com/articles/spotlight/251/updates-to-un-ece-regulation-on-advanced-emergency-braking-systems-for-heavy-vehicles-published (Accessed: 21 September 2026).

Volvo Trucks (2024) Volvo Trucks launches next-generation safety systems to protect pedestrians and cyclists. Available at: https://www.volvotrucks.com/en-en/news-stories/press-releases/2024/oct/volvo-trucks-launches-next-generation-safety-systems-to-protect-pedestrians-and-cyclists.html (Accessed: 21 September 2026).

Mercedes-Benz Trucks (2026) Assistance systems — Active Brake Assist 6 Plus. Available at: https://www.mercedes-benz-trucks.com/int/en/sustainability-and-innovation/solutions/assistance-systems.html (Accessed: 21 September 2026).

Euro NCAP Commercial Vehicles (2025) Driving change: Euro NCAP elevates safety standards for European trucks. Available at: https://commercial-vehicles.euroncap.com/press-media/driving-change-euro-ncap-elevates-safety-standards-for-european-trucks/ (Accessed: 21 September 2026).

Euro NCAP (2026) Euro NCAP reveals fatal flaws in trailer underrun safety that cost 400 lives every year. Available at: https://www.euroncap.com/press-media/euro-ncap-reveals-fatal-flaws-in-trailer-underrun-safety-that-cost-400-lives-every-year/ (Accessed: 27 September 2026).

Commercial Motor (2026) Euro NCAP to call for urgent changes to European trailer safety rules. Available at: https://www.commercialmotor.com/news/article/euro-ncap-to-call-for-urgent-changes-to-european-trailer-safety-rules(Accessed: 27 September 2026).

Motor Transport (2026) "Devastating flaws" on UK and European trucks cause hundreds of road deaths a year, investigation reveals. Available at: https://motortransport.co.uk/industry-news/devastating-flaws-on-uk-and-european-trucks-cause-hundreds-of-road-deaths-a-year-investigation-reveals/90668.article (Accessed: 27 September 2026).

Insurance Institute for Highway Safety, cited in Cycling News (road.cc) (2025) Cyclists' hi-vis clothing invisible to some car brands' automated emergency braking systems, shocking crash prevention study finds. Available at: https://road.cc/content/news/hi-vis-invisible-some-car-braking-systems-312637 (Accessed: 21 September 2026).

Smart Cities Dive (2022) Automatic braking systems have trouble seeing pedestrians at night: IIHS test. Available at: https://www.smartcitiesdive.com/news/automatic-braking-pedestrians-night-iihs-test/630818/ (Accessed: 21 September 2026).

University of Tennessee, Center for Transportation Research (2024) No Longer in the Dark: Khattak and Moradloo Evaluate Nighttime Performance of Pedestrian Automatic Emergency Braking Systems. Available at: https://cee.utk.edu/no-longer-in-the-dark/ (Accessed: 21 September 2026).

Consumer Reports (2024) Guide to Automatic Emergency Braking. Available at: https://www.consumerreports.org/cars/car-safety/automatic-emergency-braking-guide-a1780056935/ (Accessed: 21 September 2026).