The function of the rear deceleration collision barrier device of the car
The rear collision mitigation device of a vehicle, usually referred to as a TMA (Traffic Management Attenuator) or a crash buffer vehicle, primarily functions to absorb and dissipate the impact energy in rear-end accidents, thereby reducing the risk of injury to personnel, equipment, and passengers in the rear vehicle.
Main functions:
Absorbing impact energy: Through the controlled deformation of internal energy-absorbing materials (such as aluminum honeycomb, hydraulic damping systems, crush cores, etc.), kinetic energy is converted into heat energy and deformation energy, significantly reducing the impact force.
Extending collision duration: According to the impulse theorem (change in momentum = force × time), prolonging the collision time can significantly reduce the average impact force. A normal collision lasts about 0.1 seconds, while the collision mitigation device can extend the time to 0.3–0.8 seconds, reducing the acceleration from fatal 50g+ to within the human tolerable range.
Protecting personnel in front: In scenarios such as road construction and accident handling, this device is installed at the rear of engineering vehicles or dedicated crash buffer vehicles to provide a "moving safety barrier" in front of the work area, preventing out-of-control vehicles from directly entering the work zone.
Reducing secondary injuries: The structural design ensures no flying debris after the impact and that the energy-absorbing components collapse inward, avoiding secondary penetration or severe deformation for the rear vehicle.
Enhancing safety redundancy: When used in conjunction with reflective cones, warning lights, LED screens, etc., it forms a multi-level protection system of "warning – buffering – blocking".
Typical application scenarios:
Highway maintenance operations
Accident scene handling
Emergency closure of tunnel entrances (such as the water curtain flexible barrier system in Zhejiang)
Parking lot crash barriers (low-speed flexible protection)
Technical features
Compliant with international standards: such as the US MASH 2016, NCHRP Report 350, etc.
Modular design: foldable and retractable for easy transportation and deployment
Multi-sensor integration: some high-end models are equipped with radar, cameras, Bluetooth, rearview systems, etc.
Note: The term "rear collision mitigation device failure" does not have a direct corresponding professional term or standard system name in public materials. Based on current mainstream automotive safety systems and public materials, it may involve the following two scenarios:
If referring to "Collision Mitigation Braking System" (CMBS) failure
CMBS (Collision Mitigation Braking System) is the term used by brands like Honda for the forward collision warning and automatic braking system, used for forward collision prevention, not specifically for "rearward".
If the dashboard indicates "CMBS failure" or similar warnings, it usually means:
The front radar or camera is blocked, dirty, or damaged;
The control unit or wiring of the system is faulty;
Brake fluid shortage, severe wear of brake pads, etc., affecting the operation of the braking system.
Note: CMBS mainly addresses forward collisions, not specifically "rearward deceleration collisions".
If referring to "rear collision warning" or "reverse automatic braking" system failure
Some models are equipped with rear cross-traffic warning (RCTA) or reverse automatic braking functions, belonging to rearward collision auxiliary systems. If this system reports a failure, possible reasons include:
The rear radar/sensors are blocked or damaged;
The rear camera system is abnormal;
Parking brake-related components are faulty (such as switches, sensors, modules);
Short circuit or communication failure of the control unit.
Suggested handling steps Stop immediately for inspection: Confirm if the vehicle is in a safe condition and turn on the double flashing hazard lights.
Check the specific fault codes or text prompts on the dashboard: Different brands have different descriptions (such as "Collision Warning System Fault", "RCTA Off", etc.).
Check the sensor area: Are the front and rear radars and cameras blocked by mud, snow, stickers, etc.?
Avoid high-speed driving or emergency braking: Before the fault is resolved, drive carefully.
Go to a professional repair shop as soon as possible: It is recommended to go to a brand-authorized 4S store or a regular repair facility with diagnostic equipment, use a dedicated diagnostic instrument to read the fault codes, and accurately locate the problem.
If the vehicle is of brands such as Honda, Acura, Toyota, Lexus, etc., the rear collision avoidance system is usually called RCTA (Rear Cross Traffic Alert) or BSM (Blind Spot Monitoring), and the manual should be consulted for specific models to confirm.
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