Following its announcement of UK based research which showed 71% of drivers worldwide believe they can purchase a self-driving car immediately, Euro NCAP has detailed how it assesses automated driving technology.
As part of a commitment to independently assess the benefits of new vehicle safety technologies, the organisation tested the comparative performance of so-called highway assist systems in 10 cars: the Audi A6, BMW 5 Series, DS 7 Crossback, Ford Focus, Hyundai NEXO, Mercedes-Benz C Class, Nissan Leaf, Tesla Model S, Toyota Corolla and the Volvo V60.
Highway assist systems combine adaptive cruise control, lane centering and speed assist systems to support the driver in driving situations on motorways.
The tests assessed and highlighted differences between systems and the varying degree of driver support each manufacturer provides.
To give potential buyers a realistic insight into the capabilities of driver assistance systems currently offered by automakers, Euro NCAP developed a series of tests to assess their performance in critical traffic scenarios simulated on a test track.
Adaptive cruise control (ACC), the system which automatically adjusts a car’s cruising speed in response to a slower moving vehicle ahead, maintaining a safe distance, operates independently of and in addition to other driver assistance systems, already assessed by Euro NCAP, such as AEB and lane assistance which continue to function in the background.
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The ACC element of highway assist is tested in an extended version of the AEB test with approach speeds that match those typically seen on European motorways. These systems are designed to adapt the speed when approaching a slower moving vehicle or one that is braking and, in general, they perform very well in such tests, Euro NCAP said.
“However, not all systems perform equally well in tests where the vehicle is approaching a vehicle which has stopped.”
The most challenging tests for these driver assist systems are the ‘cut-in’ and ‘cut-out’ scenarios. Honda Europe specifically addressed this issue early in 2015 when launching an updated, Swindon, England-built CR-V SUV model line. The automaker claimed the 2015 model year CR-V would be the first vehicle in the world equipped with a predictive cruise control system, known as intelligent adaptive cruise control (i-ACC), capable of predicting and automatically reacting to other vehicles ‘cutting-in’ to the vehicle’s lane. I-ACC uses a camera and radar to sense the position of other vehicles on the road. It then applies an algorithm to predict the likelihood of vehicles in neighbouring lanes cutting in by evaluating relations between multiple vehicles, enabling the equipped vehicle to react quickly. It complements rather than replaces traditional adaptive cruise control and reacts earlier and less drastically.
In the Euro NCAP cut-in test, a car from the adjacent lane merges into the lane just in front of the test car. This is something that happens in everyday traffic and an alert driver will typically anticipate the manoeuvre early and reduce speed accordingly. For the cut-out scenario, a car in front leaves the lane abruptly to avoid a stopped vehicle ahead, leaving the system only a short time to identify and respond to the situation.
A second set of tests has been developed to evaluate the lane centering function that continuously supports the driver to keep the car in the middle of the lane. The amount of steering support provided by each system is determined in a so-called S-bend test at various speeds. Another test measures the amount of steering effort needed by the driver to swerve around a small obstacle on the road such as a pot hole. A good driver support system will continue to support the driver during the manoeuvre and will not resist the driver or deactivate.
All automated driving tests are performed on a test track with well marked lanes and, for the cut-in and cut-out tests, make use of a robot controlled ‘dummy’ vehicle for safe testing.
Speed assist is another function that will be required if cars are to become self-driving. Current systems range from the very simple, in which the driver sets the speed to which the car should be limited, to the sophisticated. Intelligent adaptive cruise control (iACC), similar to the 2015 Honda system mentioned earlier, uses digital map data and/or visual data from a camera to identify the ‘local’ speed limit and, at the driver’s discretion, can limit the speed accordingly. Speed assist systems are currently included in Euro NCAP’s regular vehicle assessments and no further tests have been done. Only some of the cars tested were equipped with iACC.
Besides testing the system’s main functions, Euro NCAP also verifies the information provided by the manufacturer in media, commercials or in the user’s manual to check that no false or exaggerated claims are being made, and that the information on the system and its limitations is sufficiently clear and complete.
Adaptive cruise control: Both the DS and BMW offered a low level of assistance, with the driver being primarily in control. The Audi, Ford, Hyundai, Mercedes, Toyota, Nissan, Volvo offered a balance between driver and system assistance. The Tesla risked an over reliance on the assistance system with the vehicle being primarily in control.
Steering: In the S-bend test, a range of different driver assistance levels was encountered but the Tesla system created the potential for over reliance. In the small obstacle ‘pot hole’ scenario, all the cars tested allowed the driver to cooperatively steer and manage the situation apart from the Tesla. The Tesla system did not allow the driver to deviate from the lane centering path and will disengage when a driver inputs steering torque. Again, this risked over reliance on the system by the driver.
Cut in and Cut Out: Cut-in and cut-out scenarios are the most challenging of Euro NCAP’s tests and all of the cars were found to be seriously lacking. None of the systems were able to help and crashes could only be avoided if an alert driver braked or steered away from trouble. These challenging scenarios highlight the importance of the driver remaining attentive and not over-relying on the system.
User manual and marketing information: User manuals generally state clearly what the system limitations are and where they should be used. None of the systems restricted use by geofencing. Generally, official marketing content is clear in what the role of the driver is but, in BMW’s case, a promotional video for the 5 series is misleading as the driver takes their hands off the wheel where it is assumed that the vehicle can drive autonomously. Tesla uses a number of promotional videos which also suggest vehicle autonomy. This creates a mismatch between more accurate information included in the user manual and more misleading information in marketing materials.