Study: Most Automaker Partial Automation Driving Systems Need Improvements

The Insurance Institute for Highway Safety has conducted its first major test of partial-automation driving systems. In a battery of tests evaluating driver-assist features for seven different parameters, the agency gave not one of 14 tested systems its top rating of good; only one earned an acceptable rating, two rated marginal, and the remaining 11 all ranked poor.

Related: These 71 Cars Earned IIHS Top Safety Pick Awards Amid Tougher Criteria

Automakers for the most part shy away from describing any high-tech driver-assistance features as autonomous or self-driving, but what IIHS defines as “partial driving automation” systems are available from nearly every major brand. Such systems at the very least combine adaptive cruise control and lane-centering steering, and they may include myriad other driver-assistance features. IIHS noted that while these technologies are not self-driving, “automakers sometimes use names that imply their systems are.” Furthermore, says IIHS president David Harkey, “there is little evidence [partial automation] makes driving safer,” going on to observe that “as many high-profile crashes have illustrated, it can introduce new risks when systems lack the appropriate safeguards.”

Vehicles and Systems Evaluated

IIHS evaluated 14 different partial-automation systems from nine manufacturers, and while the agency says its ratings only apply to the specific models tested, it also notes that “systems with the same names may be used on multiple vehicles from the same manufacturer.” Harkey criticized most of the systems for failing to “include adequate measures to prevent misuse and keep drivers from losing focus on what’s happening on the road.” The overall ratings for the systems and the specific vehicles tested are as follows.

Acceptable

• Lexus Teammate with Advanced Drive, 2022-24 Lexus LS

Marginal

• GM Super Cruise, 2023-24 GMC Sierra
• Nissan ProPilot Assist with Navi-Link, 2023-24 Nissan Ariya

Poor

• BMW Active Driving Assistant Pro, 2023-24 BMW X1
• Ford Adaptive Cruise Control with Stop & Go and Lane Centering Assist, 2021-24 Ford Mustang Mach-E
• Ford BlueCruise, 2021-24 Ford Mustang Mach-E
• Genesis Highway Driving Assist 2, 2023-24 Genesis G90
• Genesis Smart Cruise Control/Lane Following Assist, 2023-24 Genesis G90
• Lexus Dynamic Radar Cruise Control with Lane Tracing Assist, 2022-24 Lexus LS
• Mercedes-Benz Active Distance Assist Distronic with Active Steering Assist, 2022-23 Mercedes-Benz C-Class
• Nissan ProPilot Assist 2.0, 2023-24 Nissan Ariya
• Tesla Autopilot Version 2023.7.10, 2021-23 Tesla Model 3
• Tesla Full Self Driving (Beta) Version 2023.7.10, 2023-23 Tesla Model 3
• Volvo Pilot Assist, 2022-24 Volvo S90

IIHS evaluated driver-assistance systems in seven categories: driver monitoring, attention reminders, emergency procedures, safety features and three driver involvement categories (lane changes, adaptive cruise control resumption and cooperative steering).

Driver Monitoring

Some partial-automation driving systems include driver-monitoring technology, which relies on sensors that either detect whether a driver’s hands are on the steering wheel or track the driver’s eyes with a camera to make sure they’re on the road. IIHS recorded what happened when the driver-monitoring camera’s lens was blocked or the driver’s face was obscured, the driver was looking elsewhere and when their hands were not on the wheel. For systems that promise hands-free driving, the agency also recorded what happens when the driver was holding a foam block the rough size and shape of a smartphone.

IIHS does not believe partial-automation systems should activate in any of these conditions, and if they’re already activated, they should issue an alert under these conditions. None of the tested systems met this standard. Both Ford systems detected when the driver’s face or the camera lens was obscured but failed to react to the driver’s hands being off the wheel. Systems from BMW and Mercedes had the opposite problem, reacting appropriately when the driver took their hands off the wheel but not when their eyes were averted (the Mercedes system does not use a driver-monitoring camera).

Attention Reminders

Per IIHS standards, vehicles should issue what the agency calls a dual-mode alert — such as audible and visual warnings — within 10 seconds of detecting that the driver’s eyes are off the road or their hands off the steering wheel. Within 20 seconds, IIHS believes a third type of alert should be issued. Some manufacturers’ systems can vibrate the driver’s seat, while others tap the brakes to get their attention.

Both Ford systems earned a good rating in this test, as did GM’s Super Cruise and Lexus Teammate. The two Nissan systems and Tesla’s Full Self Driving rated acceptable, while the rest scored a poor rating.

Emergency Procedures

If the driver does not respond to any of these alerts, IIHS believes the vehicle should begin emergency procedures to slow the vehicle within 35 seconds; the agency said drivers who ignore alerts for that amount of time are either in distress or misusing the system. In addition to automatically slowing the vehicle, IIHS wants the driving-assistance tech to send an SOS message either to first responders or a 24-hour call center, as well as disabling the autonomous system for the remainder of the drive.

Only GM’s Super Cruise met expectations in this test. The systems from BMW, Mercedes, Tesla and Lexus took two of the three desired steps, netting them acceptable ratings. Both Nissan systems, both Ford systems and Volvo Pilot Assist performed just one function and ranked marginal. The rest scored poor for failing to take any emergency action in reaction to an unresponsive driver.

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Safety Features

Seeing as automatic emergency braking and lane departure prevention are fundamental elements of a self-driving car, IIHS says such safety features must remain enabled for any level of partial autonomy to work. Additionally, the agency wanted to see if the systems engaged without the driver’s seat belt being buckled. For a good rating in this category, the automation system could not engage if either AEB or LDP is turned off or the driver was not belted. It must also be impossible to switch off AEB and LDP when the automation system is operating; if the driver unbuckles their seat belt, the system should initiate its sequence of driver warnings.

GM’s Super Cruise, Nissan’s ProPilot Assist 2.0 and Lexus Teammate were the only systems to rate good in this test. Nissan’s lesser system and BMW Active Driving Assistant Pro ranked acceptable, as both deactivated when AEB or LDP was disengaged; however, IIHS pointed out they did so without a clear alert that the full system had been disabled, potentially creating a situation where the driver is unaware that they have complete control of the vehicle. The Volvo Pilot Assist system, for example, disengaged when the driver unbuckled their seat belt but issued no warning it had done so.

Driver Involvement

This series of tests focuses on what these systems will and will not do without some degree of driver interaction. IIHS believes that lane changes should always be initiated or at least confirmed by the driver; that adaptive cruise control should not resume after a full stop unless the system can confirm the driver is looking at the road and the car has been stationary for no longer than two minutes; and that lane-centering steering should remain engaged even if the driver makes minor steering corrections within their lane.

Here, IIHS recorded more satisfactory findings than in the rest of the testing. Most of the systems tested met expectations regarding lane changes and steering assist, with only GM’s Super Cruise and Tesla’s Full Self Driving systems changing lanes free of driver input (touted by both automakers as a feature). Those two, along with Tesla’s Autopilot, were also the only ones to disengage in response to driver steering inputs. While better than results in tests not evaluating driver involvement, results in the adaptive cruise control assessment were still highly varied, reflecting different beliefs among automakers on how such systems should work.

Dangerous Inconsistency

Those varied beliefs are, more than technical shortcomings, perhaps the most important discovery of the testing, which highlights the inconsistent philosophies behind and intentions of such systems. Particularly when it comes to conditions under which the systems disengage (or not) and how they alert the driver (or not), it’s not hard to see the potential for danger — particularly if you imagine a household in which two or more vehicles have these systems, but their operating parameters differ.

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