Which car has the best self-driving tech?

With a view towards taking the stress out of motoring, the scope of assisted driving tech has progressed rapidly in recent years. A huge range of systems is now offered on new cars, either as standard equipment or as an option, and we wanted to find out how far they have evolved. Are the systems competent enough to ease the driver’s workload? Or might drivers be tempted to rely on them too much?

We chose 10 cars of various shapes and sizes to test, including the comparatively affordable Toyota Yaris and the Kia EV6 (our 2022 Car of the Year), with the newest contender being a Range Rover Sport. While a range of manufacturers is included in our group, it’s worth noting that Mercedes is absent because it didn’t have a car available on the day of our test, and Volvo said it doesn’t permit the testing of its active safety systems for comparative purposes. This is perhaps a surprise, given the brand’s strong attitude towards safety. So, we sourced a privately owned Volvo XC60.

Each of the cars has adaptive cruise control fitted (this maintains a set speed and distance from the vehicle ahead) and an active steering assist system that helps keep the vehicle stay in the centre of the lane. To find out how easy they are to use and evaluate how well they work, we subjected them to four standardised simulated tests devised by the safety experts at Thatcham Research.

First up is the S-bend test. In this, the car starts off travelling in a straight line before the road gently curves into a left-hand bend before arcing to the right and straightening back out again. To pass the test, the car’s active steering assist simply has to keep the car within in its lane throughout the manoeuvre at 50mph, 62mph and finally 75mph.

The pothole test involves a section of single-lane road where the vehicle is driving towards an object that mimics a pothole, with both assisted-driving systems activated. It’s designed to show how the systems respond when the driver takes over the steering to avoid a pothole; ideally, the system should let the driver make a brief steering input before the car reassumes a position in the centre of the lane and continues as before. This test is performed at 50mph, 62mph and 70mph.

The hands-off test comes next. In the UK, it is a legal requirement to drive with your hands on the steering wheel at all times, even when assisted driving systems are in use. This test concerns the systems that monitor steering input; we’re looking at what happens when warnings to retake the wheel are unheeded.

Finally, the emergency stop test demonstrates how the systems cope when the car detects a stationary vehicle ahead at the very last moment. Each car follows another moving vehicle on a straight road with the adaptive cruise control set to 30mph. The leading vehicle then moves across to the next lane to suddenly reveal a stationary car, requiring our test car’s systems to perform an emergency stop. This test is also repeated at a higher speed of 42mph.

So, which car has the best systems? Is the most expensive car the best performer? Let’s brace ourselves to find out.

S-bend test

Only four of the cars managed to successfully complete this test at all three speeds. The Tesla Model Y was the most competent performer, responding the most quickly to the curving lane markings and maintaining an accurate central position at 50mph. Only during the two higher-speed tests did it run wide and get close to the lane markings. The Audi RS Q8, EV6 and Nissan Qashqai were also successful at all three speeds.

The BMW iX3, Ford Kuga, Volkswagen ID 5 and XC60 passed through the S-bend at speeds of up to 62mph with varying degrees of smoothness; some would steer into the bend late before zig-zagging between the lines on either side of the lane. At 75mph, though, these cars could only manage to complete the first corner of the S-bend, before running out of the lane on the second curve, with the steering assist cancelling itself altogether.

The Range Rover Sport could only successfully complete this test at 50mph, but it still finished above the Yaris, which could only successfully negotiate the first corner even at the lowest test speed.

Pothole test

All but one of these cars allow its driver to steer around a pothole without causing the assisted driving system to disable itself, at all three test speeds. The Qashqai and Kuga needed a bit of help from the driver to recentre in the lane before the steering system reactivated, but progress remained smooth. The system in the EV6 is one of the best here; there’s a little bit of resistance from the steering as you guide the vehicle around the pothole, but the system automatically centres the vehicle back into position once you let go. Even if you turn the wheel in a slightly more aggressive manner, the EV6 doesn’t panic.

In contrast, the Model Y’s behaviour proved divisive; of all the test cars, it requires the most force from the driver to override the system. Once you do, the steering assist instantly switches off. The adaptive cruise control does continue to function, though. Some will appreciate the fact that there’s a clear line between who’s in control of the Model Y’s steering: you or the car. It’s never a collaborative effort. However, others found its all-or-nothing nature disconcerting.

Hands-off test

Each of these cars deploy a series of visual and audible warnings soon after you let go of the steering wheel, and some have a few extra features to attract the driver’s attention.

The systems in the iX3, ID 5, Model 3 and Qashqai bring each car to a controlled stop within one minute of their driver taking their hands off the wheel. The iX3 is the quickest to apply the brakes (after just 20 seconds), while the Model Y takes the longest, bringing itself to a halt after 44 seconds. In addition to the initial warnings, the RS Q8 also tightens the driver’s seatbelt while it slows down.

The ID 5 also sharply tugs at the driver’s seatbelt to alert them and sounds the horn several times when the car is close to stopping. After bringing itself to a halt, the Range Rover Sport automatically shows the emergency call function on the central touchscreen for you to use, while the RS Q8 automatically dials the emergency services for you.

Rather than stopping, the Kuga slows down to 5mph and the steering assist system remains active, the theory being that this makes it easier for the driver to take over if they come around. Should that not happen, a 5mph impact will be less severe than it would be at a higher speed.

The EV6, Yaris and XC60, though, score minimal points, because their steering assist functions soon switch themselves off if no steering input is forthcoming after a warning is issued, leaving the vehicle to continue driving without human supervision. At least the XC60 slows down to a constant 7mph; the other two continue at whatever speed you’ve programmed into the adaptive cruise control.

Although the Range Rover Sport promptly slows itself down if warnings are ignored, it earns only a mid-table score. That’s because, once it has commenced its emergency stop procedure, it responds very hesitantly when you try to override the system, even if you floor the accelerator pedal. This leaves you vulnerable to traffic approaching from behind.

Emergency stop test

At 30mph, all but one of our cars managed to come to a halt in time to avoid colliding with the stationary vehicle ahead. The ID 5 is the only one that didn’t, although its automatic braking system had started to reduce speed and, therefore, the severity of the impact.

In the 42mph test, the Model Y was the only car that stopped in time to avoid striking the stationary vehicle. Of all of the other cars that identified the hazard and automatically applied the brakes, none slowed enough to avoid contact, instead striking the stationary car with enough force to damage both cars.

However, at 42mph, two cars failed to react to the stationary vehicle ahead at all; the Range Rover Sport and XC60 both struck the stationary vehicle without slowing.

Ease of use

How easy these systems are to use will affect how likely the driver is to use them. The Model Y’s systems deserve praise for being particularly simple; you just flick the gear selector stalk down once to activate the adaptive cruise and then again for lane keeping. From that point, adjusting the speed and distance from the vehicle ahead of you is a case of simply rotating or nudging the control dial on the right spoke of the steering wheel.

The RS Q8’s system is also a cinch to operate, with a separate stalk mounted on the steering column. Most of the remaining cars here have simple physical buttons on the steering wheel to operate the systems, but the ID 5’s touch-sensitive controls are extremely difficult to press accurately, leaving the driver unclear as to whether they’ve activated the desired function. This might discourage them from using the systems at all.

From a visual point of view, the Model Y also has an advantage, displaying a large, clear graphic on its centre screen, continuously feeding information about the car’s surroundings – including road markings, other vehicles and pedestrians – to the driver. This means, when an audible warning goes off, you’ll at least understand what it’s referring to. Other cars here show smaller warning signs on the driver’s instrument panel, leaving you to second-guess the exact cause of the systems’ reactions.

Verdict

There’s a big gulf in performance between the best and worst of today’s assisted driving systems. The Tesla Model Y and Audi RS Q8 gain the highest overall score, but the Model Y was the only car to score points in all of the tests, being the only one to perform the emergency stop test at 42mph.

The Toyota Yaris finishes at the bottom of the table, but it’s worth noting that it’s by far the least expensive car here, so it can’t be expected to be equipped with the most advanced technology.

Looking at the rest of the results demonstrates that the most expensive or newest cars won’t necessarily possess the most advanced or best-performing systems.

What’s next for self-driving technology?

The vision is that assisted driving will eventually develop to enable full self-driving, with the benefit of unlocking road safety benefits and freeing up the time we spend travelling. Much work has already been done by international regulators and the UK Government to pave the way for development. However, the limits of current technology and uncertainties over liability mean there’s a gulf between the vehicle assisting its driver and it being allowed to assume full responsibility for safe driving.

Colin Grover, principal engineer for automated driving at Thatcham Research, explained how we can expect the technology to evolve over the coming years. “A potential stepping stone to self-driving on UK motorways is ‘hands-free, eyes-on’ assistance,” he said. “This has been available in the US since 2017, pioneered by Cadillac’s Super Cruise and Ford’s BlueCruise systems. In use, these are like the advanced assistance systems in the cars participating in our tests today, but they allow hands-off operation, using sensors to oversee driver attentiveness.”

He went on to explain that a better understanding of driver behaviour could hold the key to implementing technology that could improve road safety, unlocking opportunities to tune assistance systems for effectiveness and driver acceptance.

While it should be emphasised that the systems currently available in the UK depend on driver supervision for safety, self-driving is already a reality in controlled situations in Europe. “Mercedes offers its Drive Pilot system in Germany, where it can act as a low-speed traffic chauffeur on autobahns,” said Grover. “For more widespread operation, though, systems will require adaption for local traffic conventions, signage and so on, to suit every country’s legislation.”

For all the latest reviews, advice and new car deals, sign up to the What Car? newsletter here

Read more: What's it like to drive a fully autonomous car? >>