Mercedes S320 CDI

Safety technology is typically introduced on expensive cars before it filters down to cheaper models, so it’s no surprise that this range-topping Mercedes
is packed with goodies.

In fact, the big S-Class saloon pioneered the use of anti-lock brakes in passenger cars. The innovation was originally designed for aeroplanes, and an early mechanical anti-lock set-up appeared on the Jensen FF sports car in 1966. But the first completely electronic four-wheel ABS system was developed by Bosch, and debuted on the S-Class in 1978.

In common with many of its rivals, the current flagship Merc is packed with safety features. It comes with the Adaptive Brakes package, which comprises several elements. Firstly, Brake Drying applies a tiny amount of pressure between the pad and disc in wet conditions to ensure the disc is dry at all times.

Brake Priming also ensures the pads make slight contact with the disc as soon as your foot comes off the throttle. This helps to reduce the braking distance in any subsequent emergency stop. Brake Assist senses the speed at which you apply the brake and automatically increases servo assistance.

All this technology is common to many manufacturers, but the really clever piece of kit on the S-Class is the optional Brake Assist Plus. This uses the radar sensors of the Distronic cruise control to calculate optimal braking power. It takes into account the proximity of other cars and makes adjustments to brake pressure accordingly.  

The LED brake lights also flash during hard braking to alert following drivers, and the hazards come on in an emergency stop.

Regardless of its clever software, a car as heavy as the S-Class needs serious braking hardware. Mercedes has fitted large vented discs up front, while the tyres have a big footprint.

From behind the wheel, the S320’s stability under braking is reassuring. A 47.7-metre stop in a straight line is brilliant, but it’s in the lane change where the Merc really impresses. Despite weighing two tonnes, it avoided the wall and returned to the original lane in all three of our runs with ease.

Under hard braking the nose dips, while the direction change is assisted by responsive steering. Stability control ensures there’s no sudden loss of grip, and the Pre-Safe system tightens the seatbelts and moves the seat base up to hold you in position.

This superb braking performance, plus the long list of active safety equipment, means the S-Class remains one of the safest cars in the world.