Quick Guide
You can jump instantly to the main sections of this guide using the links below:
Understanding Collision Avoidance
Collision avoidance systems are designed to help the driver recognise a potential collision and respond before it occurs. Depending on the technology fitted, the vehicle may warn the driver, prepare the braking system or automatically apply the brakes.
Two of the most commonly encountered technologies are Forward Collision Warning (FCW) and Autonomous Emergency Braking (AEB).
Forward Collision Warning ('FCW')
Forward Collision Warning (or 'FCW') monitors the road ahead and can warn the driver when it detects that the vehicle may be approaching another vehicle or road user too quickly.
Depending on the system, the warning may be visual, audible or use another form of alert. The intention is to give the driver additional time to react, for example by reducing speed, braking or taking other appropriate action.
FCW is primarily a warning system. It should not be assumed that a vehicle fitted with Forward Collision Warning will automatically apply the brakes if the driver does not respond.
Click here to go back to the top of the page
Autonomous Emergency Braking ('AEB')
Autonomous Emergency Braking (or 'AEB') goes a stage further than a warning system by allowing the vehicle to apply the brakes automatically when the system determines that intervention is required.
What AEB Can Detect
The capabilities of AEB depend upon the system fitted to the vehicle. A vehicle described as having AEB should not therefore be assumed to detect every type of road user or potential collision.
Depending on the system, AEB may be designed to detect vehicles ahead and other road users such as pedestrians and cyclists. Some systems may also operate in a wider range of situations.
How AEB May Intervene
When an AEB system identifies a potential collision, it may prepare the braking system or automatically apply the brakes if the system determines that intervention is required.
The purpose of the intervention may be to avoid the collision where possible or to reduce the vehicle's speed before impact. How and when the system intervenes depends upon the system fitted, the driving situation and the conditions in which it is operating.
How FCW and AEB Work Together
AEB and FCW may work together as part of the same collision avoidance system. A driver may initially receive a collision warning, giving them an opportunity to respond, with automatic braking following if the system determines that further intervention is required.
Click here to go back to the top of the page
Understanding the Limitations
Collision avoidance technologies should not be regarded as a guarantee that a collision will be prevented. Their ability to detect a hazard and respond appropriately can depend on the design of the system, vehicle speed, road layout, visibility, weather conditions and the type and movement of the road user involved.
The driver is therefore still responsible for controlling the vehicle and responding to road conditions, even when collision avoidance technology is fitted.
Weather, Visibility and Road Conditions
Weather and visibility can affect the ability of some collision avoidance systems to detect potential hazards. Heavy rain, snow, fog, poor visibility or strong sunlight may affect the information available to cameras, radar or other sensors.
Road layout, bends, gradients and the position or movement of other road users can also influence whether a potential collision is detected and how the system responds.
The effect of these conditions varies between systems and the technologies they use. FCW or AEB should therefore not be assumed to detect or respond to every potential hazard in all weather, visibility or road conditions.
Sensors, Repairs and Recalibration
Collision avoidance systems can rely on cameras, radar and other sensors positioned around the vehicle. These need a sufficiently clear view of their surroundings, and dirt, snow, damage or other obstructions can affect the operation of some systems.
Repairs or replacement of components associated with ADAS equipment may also affect the operation of these systems. Depending on the vehicle, work involving items such as windscreens, bumpers, cameras, radar or other sensors may require the relevant systems to be checked and, where necessary, recalibrated.
The requirements vary between vehicles and systems, so the appropriate vehicle manufacturer and repair information should be followed.
Click here to go back to the top of the page
Collision Avoidance and Vehicle Safety Ratings
Collision avoidance technologies form an important part of modern vehicle safety assessment. Euro NCAP considers the performance of driver assistance technologies as part of its assessment of cars and commercial vehicles.
This can include systems designed to identify potential collisions involving other vehicles and vulnerable road users such as pedestrians and cyclists, together with technologies that can warn the driver or intervene to help avoid or mitigate a collision.
The presence of a particular technology does not by itself determine a vehicle's overall safety rating. Vehicle safety assessments consider a range of safety systems and their performance as part of the wider assessment of the vehicle.
Independent Vehicle Information
DriveSmart provides independent information designed to help motorists, self-employed drivers, businesses and fleet operators understand vehicle ownership.
Our searchable vehicle databases combine technical specifications, taxation, running costs, grants and safety information, allowing users to compare vehicles using consistent, structured data.
Whether you are choosing a family car, an electric company car or a commercial van, our aim is to help you understand the facts before making your decision.
Our Vehicle Safety Hub Is Growing
DriveSmart continues to expand its Vehicle Safety Hub with additional guides covering modern vehicle safety technologies, commercial vehicles, electric vehicles and independent safety information.
As new vehicle assessments become available, our searchable databases and supporting guides will continue to develop.
Important Safety Information
Advanced Driver Assistance Systems are designed to assist the driver. They do not replace the need for the driver to remain attentive, maintain control of the vehicle and respond appropriately to road, traffic and weather conditions.
The availability, operation and limitations of individual ADAS technologies vary between vehicles, manufacturers and vehicle specifications. Drivers should familiarise themselves with the systems fitted to their vehicle and follow the information and instructions provided by the vehicle manufacturer.
No driver assistance system should be relied upon to prevent a collision or to operate correctly in every situation. The driver is still responsible for the safe operation and control of the vehicle at all times.
Click here to go back to the top of the page
Explore Euro NCAP Safety Ratings