Car lane support systems tested

Lane support systems get a lot of bad press, but they could help save your life. We invited five readers to try some of the latest to see if they inspire confidence or merely annoy...

Lane support system reader test team

Just as a seatbelt is no help whatsoever if you refuse to wear it, driver assistance systems are pointless if they’re switched off.

That's the stark reality underpinning recent studies by Thatcham Research. As a member of Euro NCAP – the independent organisation that encourages ever-higher standards of new car safety across Europe – Thatcham seeks to make sure people don’t find such technology a turn-off. 

Most recently, it has put lane-support systems (the umbrella term for advanced driver aids such as lane-keeping assistance and lane-departure warning) under particular scrutiny, having received adverse feedback from many drivers who’ve used them.

As part of its research, it has tested lots systems. The image below is a staged collision between a car and Thatcham’s 3D ‘soft target’ vehicle. It illustrates the potential consequences of a car leaving its lane at the wrong moment.

Thatcham RTT lane support systems

Lane-support technology has been with us for some years, but Thatcham has identified huge variations in how successfully it is implemented by different car brands. In too many cases, drivers switch it off because they find it too frustrating or intrusive – defeating the purpose of it being fitted. 

A comparison between lane-departure warning and forward-collision warning systems illustrates this point. In a US study of Honda cars, inspectors visited the brand’s workshops over four weeks. They found that 183 cars out of 184 checked (99.5%) had their forward-collision warning systems turned on. In contrast, in a sample of 265 cars, the lane-departure warning on only 87 cars (32.8%) was found to be active. 

This is of particular concern when you consider that, whether deliberate or accidental, lane deviation is a factor in around one in five fatal collisions. In other words, if the car had stayed in its original lane, the accident wouldn’t have happened. 


Lane-support tech explained 

Lane-support tech works in a few different ways, depending on the car model and the manufacturer. Some systems (including the one fitted to the Volkswagen Golf GTI in our tests) are wholly image-based and rely on cameras to identify road markings. Others (including on the Mercedes C-Class) also incorporate radar sensors.

Those sensors enable the lane-support systems to identify hazards that might exist in the adjacent lane, triggering responses on a ‘threat-dependent’ basis – from advice (warning that you’re crossing the centre line) to evasive manoeuvres (steering you back into your lane) as appropriate. Thatcham prefers threat-dependent lane-support systems, seeing them as less intrusive than those that take over whenever the centre line is crossed. 

If no hazard is identified, a threat-dependent system will still provide sensory feedback when you approach the centre line. However, it won’t stop you crossing into the adjacent lane, as you might when avoiding a pothole or a parked car, or if you want to ‘straighten out’ a bend in the road when it’s safe to do so.


Readers' verdicts on five of the latest lane-support systems

Thatcham RTT lane support systems

We invited five members of our reader test team to sample a selection of the latest lane-support systems and tell us what they think of them. Here they give us their verdicts and pick the one they believe performs the best. 

John Armstrong-Denby 

Age 47 Job Finance director Drives 2020 Land Rover Discovery, 2006 Porsche 911 Cabriolet 

“Although my 911 is too old to have many electronic aids, my Discovery is loaded with all the latest toys, including lane-keeping assistance and automatic emergency braking [AEB], and I use the systems a fair bit, especially on motorways and dual carriageways. Its lane-keeping assistance works well, but having tried the lane-support systems in the cars in this test, I have to concede that those in the Mercedes C-Class and Polestar 2 are more sophisticated and easier to live with. 

“The Mercedes system in particular really gels with the driving experience, cutting in when necessary but not bothering me at other times. Even though I’ve never been a huge Mercedes fan, it’s the best system here. 

“The Polestar’s system was also good, being natural and balanced in its application. It’s just a bit more overt than the Mercedes one, so it would take a bit of getting used to. 

Thatcham RTT lane support systems

“Of the others, I found the Toyota RAV4 one the least useful – it was barely noticeable when it cut in. Although this might suit some people, I’d worry that it could be ignored and drivers might not make full use of it. 

“The Golf GTI was at the other end of the spectrum. It was so extreme when it activated that I felt it was too aggressive and found it rather off-putting. 

“For me, assistance systems should always work in the background rather than dominating the driving experience. They should allow you to make decisions for yourself, such as being able to cross the broken white lines when it’s safe to do so.” 

Favourite system Mercedes C-Class 


Rav Baines

Age 51 Job Company director Drives 2019 Volvo XC90 

“My car has a suite of active safety features and I leave them all switched on. I think it’s great that Volvos have more advanced driver aids than many other cars. The brand doesn’t make enough noise about them. 

“Of the cars here, some brands seem to have skimped on how lane-keeping assistance is implemented. I found the system on the Mercedes best, because it felt unobtrusive. It nudged the car back to a safer position on the road rather than forcing it. The Golf, on the other hand, was too assertive for my liking and felt like it was treating its driver like an idiot. 

Thatcham RTT lane support systems

“A head-up display proved helpful by making the lane-support graphics more visible in the windscreen. The cars fitted with head-up displays in this test [the Hyundai Ioniq 5, Mercedes C-Class and Polestar 2] provided a clearer view of where they were in relation to the lane and the roadside. 

“All car makers should ensure their lane-support systems inspire confidence rather than dent it. In particular, cheaper cars should have well-sorted systems, because they’re the volume sellers and that means the technology will reach the widest possible audience, keeping more drivers safe at those rare moments when their mind is elsewhere while they’re driving.” 

Favourite system Mercedes C-Class