Under the microscope: new assist systems for active safety: Protection against the blind spot, help when changing lanes

Oct 4, 2010
Active Blind Spot Assist warns the driver if it detects a risk of collision when changing lanes. Short-range radar sensors housed on both sides of the rear bumper monitor the areas directly alongside and behind the car.
This process enables them to see if there is another vehicle in the next lane –
in the so-called blind spot. In such situations, the system informs the driver by illuminating a red warning signal in the glass of the exterior mirror. If the driver fails to see this warning and indicates to change lanes, a warning signal sounds as well.
In an innovation from the latest stage of development, if the driver ignores warnings and the vehicle comes dangerously close to the next lane, Active Blind Spot Assist will intervene. Applying braking force to the wheels on the opposite side of the vehicle via the Electronic Stability Program ESP® creates a yaw movement which counteracts the collision course. The system intuitively deactivates as soon as the driver steers against the effects of the braking intervention or the vehicle accelerates.
If an accident can no longer be avoided in spite of correcting the direction, Active Blind Spot Assist can mitigate the consequences of a collision through course correction. Where the system detects vehicles or obstacles just a short distance away on the opposite side, it will adapt its braking intervention accordingly. To do so, Active Blind Spot Assist also uses data from the front sensors for DISTRONIC PLUS proximity control.
Brake actuation to correct the course occurs between 30 and 200 km/h. The effect is limited to longitudinal and latitudinal deceleration of 2 m/s2. When ESP® is in OFF mode, Active Blind Spot Assist is switched off. Visible warning in the exterior mirror is active up to a speed of 250 km/h.
Active Lane Keeping Assist with ESP® support
Active Lane Keeping Assist is now also linked to the ESP® for the first time. This system kicks into action if the Mercedes vehicle inadvertently drifts over a solid line to the right or left of a lane. In this case, Active Lane Keeping Assist uses the ESP® to brake the wheels on the far side in order to prevent the vehicle from crossing the line and to bring the vehicle back on course. A display on the instrument cluster warns the driver at the same time. If broken lane markings are crossed, the system controls an electric pulse generator in the steering wheel which generates vibrations for a short time – a discreet but highly effective cue to countersteer immediately. Before the braking system intervenes, the steering wheel always vibrates to provide a haptic warning.
Active Lane Keeping Assist is based around a camera on the inside of the
windscreen. It is able to recognise lane markings by analysing the difference in contrast between the road surface and the boundary lines. The image processing solution informs an electronic control unit which determines and detects the position of the vehicle if it drifts out of this lane to the left or right. For maximum reliability, the new generation of Lane Keeping Assist also evaluates radar signals in addition to image processing. Only when both lane algorithms concur is braking force applied to correct the course. Unlike conventional systems of this type, the Mercedes assistance system also assesses the behaviour of the driver and is therefore able to determine whether the vehicle is leaving the registered lane intentionally or unintentionally.
Braking intervention to correct the course occurs between 60 and 200 km/h. It does not materialise if:
  • ESP® is deactivated,
  • the radius of the bend is less than 150 metres,
  • the vehicle is driving on tyres in emergency run-flat mode,
  • when braking or accelerating by more than 2 m/s², on bends with lateral acceleration of over 2 m/s² (sporty driving style).
The steering wheel will not vibrate if the driver:
  • is accelerating before overtaking or joining the motorway,
  • brakes sharply,
  • steers into a bend,
  • cuts a corner intentionally,
  • uses the indicators,
  • is moving back into the original lane after overtaking,
  • actively countersteers.
Furthermore, Lane Keeping Assist is deactivated immediately if ABS, ESP®, Brake Assist or another active safety system intervenes.