Advanced braking systems feature on more than 370,000 commercial vehicles over 3.5 tonnes, out of a total vehicle parc of 485,000. National Highways recently questioned why these systems hadn’t reduced the number of rear-end collisions as expected – and what it found is essential information for fleet operators.

How does AEBS work?

Autonomous emergency braking systems (AEBS) either uses radar or radar plus computer-aided cameras to detect the vehicles directly in front. If the system detects the gap between its host vehicle and the one in front closing and the driver does not react, it will give an audible warning, then a haptic (touch-based) warning by sharply applying the brakes, and finally it will slam on full emergency braking to prevent or mitigate a collision. The driver can – and ideally does – interrupt this sequence at any point by taking manual control of the brakes or steering.

So what’s the problem?

Nobody is sure, frankly, but there are some key safety aspects which fleet operators need to be aware of.

• AEBS can be turned off, which is potentially useful in off-road situations, or when a snowplough is fitted etc. It will automatically turn on again after the next ignition cycle. However, it isn’t possible for fleet operators to know whether drivers are turning it off simply because they dislike the technology. (A future EU regulation will prevent AEBS being turned off above speeds of 30mph.)
• It’s also unlikely fleet operators will ever know if the system triggers unless there is a collision. The comms line for AEBS is encrypted to allow it to over-ride every other system, and as such most telematics systems can’t read it.
• If a system is triggering frequently, either the system needs to be checked by a technician, or the driver is performing in an aggressive or risky manner. Either way operators need to know so they can take appropriate action.
• National Highways is concerned that too few drivers and operators really understand these systems. They are designed as an emergency driver aid and should not be relied upon or disabled without good reason.
• By law, the systems only have to recognise a very specific shape. They will not necessarily recognise a vehicle which is offset, or partly across the carriageway. Some manufacturers add extra sensor systems to cover VRUs. However, it’s fair to expect that AEBS will probably not react to crash barriers, a fallen tree, cyclists, pedestrians, animals etc.
• Most drivers get no training on how the AEBS works, even though every system is slightly different.
• Even the best systems can be confused by challenging conditions such as dazzling sunlight, tunnels or poor visibility weather (fog, snow, sleet, rain).

National Highways has created a campaign through Driving for Better Business to advise operators and drivers about AEBS.

There are some urgent action points for operators:

1. Have a policy that drivers are trained about their AEBS, they must not turn it off without good reason and must report either turning the system off, or it triggering to their line management.
2. Coach your drivers for safety. Having analysed 350m+ pieces of fleet footage, SmartDrive Systems can clearly demonstrate that the real way to prevent collisions – rear end or otherwise – is to capture, analyse and then eliminate risky behaviours through positive and proactive coaching.

To learn more about how SmartDrive’s video-based safety analysis system can help improve your fleet safety, visit our resource centre.