Forward Collision Warning

Forward Collision Warning (FCW) is a safety feature in vehicles that helps the driver avoid collisions by warning the driver when they are getting too close to an object or vehicle in front of their car. In recent years, FCW is often bundled with the Automatic Emergency Braking (AEB) system; both of which are core components of the Advanced Driver Assistance System—a collection of safety technologies designed to assist the driver and protect the vehicle from accidents.


Most commonly, FCW systems utilise a radar and camera combination. The radar is typically located in the vehicle’s grill, and the camera is mounted on the rear-view mirror or elsewhere on the windshield. Depending on the car manufacturer, some FCW systems may use a different set of sensors, including laser technology, or in more advanced systems, LiDAR. In the near future, it is highly likely that vehicles will supplement their sensors with V2V communication to exchange data with nearby vehicles, including information about their speed, position, and direction.

How Does It Work?

The FCW camera and radar monitor the road when the vehicle is in forward motion. The FCW system keeps an eye on the host vehicle’s speed while the camera scans for obstacles ahead. The radar or a similar sensor tracks the speed of the vehicle in the path of the host vehicle. By continuously monitoring this information, the system can estimate the time-to-collision, or TTC. That’s the time it would take for the host vehicle to collide with the object if it maintains the current trajectory.

When the host vehicle is tailgating or if the vehicle in front reduces speed or brakes suddenly, the FCW will alert the driver based on alert thresholds the driver has set. These alert thresholds may vary, ranging from short to long distances. This allows the driver to customise the system’s sensitivity or switch it off completely. The intensity of the alert can vary based on the alert threshold and can increase as the TTC decreases. Using and setting the thresholds depends on the FCW system and car manufacturer.

The Warning Signs

FCW issues an alert if the distance between the host vehicle and an obstacle closes rapidly, signalling a potential collision. The alerts may be auditory (e.g., rapid beeping) or visual cues (e.g., warning flashes on the dashboard or HUD). Some systems may use haptic signals, such as a vibrating steering wheel or seat. When the system sends an alert, the driver has a few seconds, depending on the FCW, to take evasive action or apply the brakes.

AEB can automatically apply the vehicle’s brakes if the driver does not respond to the FCW warnings in time. This automatic braking can help the driver avoid a collision or at least lessen its severity. The primary objective of combining FCW and AEB is to reduce collisions caused by unexpected objects suddenly appearing in front of the vehicle.

At times, the system works too well, much to the frustration of drivers. Shadows on the road, road signs, parked cars situated in the middle of a curve by the roadside, or bending roads can occasionally trigger it.

The Driver’s Role

Driver attention is paramount, as no safety system can substitute for an alert and engaged driver. As valuable as FCW can be, it will not replace the driver’s attention or quick decision-making. When combined with AEB, it serves as an additional safety layer. If FCW issues a potential collision alert, it is the role of the driver to react promptly to avoid a possible accident.

Drivers should also be aware that FCW has its limitations and may not work properly in low-light conditions. Adverse weather conditions, such as heavy rain, snow, or fog, which affect visibility or disrupt radar signals, can also impact the system’s performance. Wet, snowy, or icy roads may interfere with radar signals as well. Ensuring that the windscreen in front of the camera is clean and the radar’s field of vision is unobstructed is essential. Furthermore, it remains the driver’s responsibility to maintain safe following distances, even with FCW enabled.

  • Collision avoidance system
  • Pre-crash system
  • Collision mitigation system
  • Forward Collision Alert
  • Front Collision Warning
  • Pre-Collision Warning
  • Forward Obstruction Warning