In the latest IISH round of evaluations, a total of 21 of 24 cars and SUVs, all 2014 models unless noted, earned an advanced or higher rating, helped by the increased use of such systems.

The move comes less than a year after the IIHS introduced its ratings programme for front crash prevention.

‘We are already seeing improvements from automakers since the initial launch of our ratings last September,’ said David Zuby, IIHS executive vice president and chief research officer. ‘BMW and Lexus, for example, have added more braking capability to their systems, which has paid off in higher ratings.’

Large family cars and large luxury cars make up the bulk of the test group. IIHS also tested four midsize luxury/near luxury cars, three midsize luxury SUVs and a midsize SUV.

Four vehicles earned full scores when equipped with certain options. They are the BMW 5 series large luxury car, BMW X5 midsize luxury SUV, 2015 Hyundai Genesis large luxury car and Mercedes-Benz E-Class large luxury car. In all, eight models earn the highest rating of superior, 13 earn advanced, and three earn a basic rating.

‘We know that this technology is helping drivers avoid crashes,’ Mr Zuby added. ‘The advantage of autobrake is that even in cases where a crash can’t be avoided entirely, the system will reduce speed. Reducing the speed reduces the amount of damage that occurs to both the striking and struck cars and reduces injuries to people in those cars.’

Euro NCAP has also started rating autonomous emergency braking systems and published its first results late last year.