Which? car testing reveals serious concerns with MG4's lane assist technology

During the course of testing the MG4 (a popular electric car from MG), we encountered a potentially significant issue relating to the car’s lane-assist system, which is designed to keep the car in lane.

Specifically, we noticed that:

• the lane-assist system twice pulled the car onto the wrong side of the road
• in another incident on a narrower country road, the lane-assist system steered the MG4 towards an oncoming vehicle
• the issues couldn’t be repeated in subsequent tests, but were significant enough for us to investigate further
• in all cases, visibility was good and the wider road had a clearly defined centre line, while the country road had a clearly defined edge line.

MG says it has developed an improved calibration of the advanced driver-assistance systems (ADAS), which will soon be approved and rolled out as a software update

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What we experienced

During tests of the MG4 on public roads, our lab testers noticed unusual behaviour with its lane-departure warning and lane-keep assistance systems.

On one occasion where the tester drove on a narrow country road and had to pass another car coming the other way, the MG4’s lane-keep assistance system steered away from the nearside edge of the road and towards the centre – and the other car. Our tester had to manually intervene to prevent the MG4 from pulling too close to the car travelling in the opposite direction.

On another occasion, this time on a wider road with a clearly defined centre line, the lane-keep assistance technology twice decided that the car had left its intended lane and pulled it onto the wrong side of the road. Using a sufficient amount of force, our tester had to manually steer the car back.

All incidents were noticed during the course of testing, but were on public roads and outside of controlled lab conditions. None of the issues could be repeated in subsequent road tests.

Is the MG4's lane assist worse than other cars?

Our lab has noted issues with the lane-keep assistance and lane-departure warning systems with other cars, but none displayed behaviour like we saw with the MG4.

The MG4 has a five-star Euro NCAP score, which takes into account active safety features such as lane assist. When asked by Which?, Euro NCAP didn’t comment specifically on the MG4 but said: ‘Vehicle manufacturers have a responsibility to ensure that the vehicle performance seen on a test track is also reflected in on-road driving.

‘In recent years, we have seen that not all manufacturers put in the same amount of effort on road evaluation of their systems. Therefore, Euro NCAP have already made a first step in 2024 regarding acceptance requirements for lane-keeping systems.

‘This will be followed by on-road evaluation procedures for 2026 and beyond, which Euro NCAP is currently developing.’

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MG’s response to our findings

Commenting on our findings, MG said: ‘We are aware of some inconsistencies relating to the lane-departure warning system which can make the system oversensitive under certain conditions.

'We have been working on a continuous improvement programme with the supplier and the relevant regulatory authorities.

‘This has resulted in an improved calibration of the ADAS systems, which we are close to having approved. Once this has been completed, we will implement it as a full software upgrade at no expense to the customer.’

What should MG4 owners do?

When asked whether owners of the MG4 should take any action, MG told us: ‘If a customer does feel this function is oversensitive in its current calibration it can be turned off via the touchscreen menu, but we would reiterate that we have had no safety-related reports from customers. A software solution to resolve the issue is very near to completion and the MG dealer network will perform the work at no cost to the customer.’

We'll monitor the situation and update this news story with more information when we have it.

What is lane-keep assist technology?

The technology goes by various names depending on manufacturer, but in general lane-keep assist is designed to keep your car in its intended lane. Precisely how it does this depends on the car in question and the settings chosen by the driver, but most cars use a combination of audible alerts to warn when the car is drifting out of lane, along with small amount of automated steering to guide it back into the intended lane (the force of these steering adjustments also varies depending on the car). 

Lane-keep assist has been mandatory on all new cars sold in the UK since 2022 and is also available on many older models.

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What is the MG4?

MG has its roots in the UK from the 1930s, but today it’s a Chinese-owned brand that specialises in family cars, including full-electric vehicles such as the MG4.

Launched in 2022, the MG4 is a popular five-door medium-sized hatchback, not least because of its relatively low price compared with other electric cars. It was also the second-bestselling electric car in 2023, according to data from industry body the Society of Motor Manufacturers and Traders (SMMT).

Despite our concerns with the lane-assist system, the MG4 impressed in several areas during our lab tests. We'll publish our full review shortly.

We want to hear from you

Have you experienced similar problems with the MG4 or any other car? Do you have strong feelings about lane and steering-assist systems more generally? If so, we want to hear from you.

Send your comments to [email protected].

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