Radar car collision prevention systems put to the test
February 15, 2008 British Motor Insurance Repair Research Centre Thatcham has put three of the car industry’s most hyped collision prevention technologies to the test – and they’ve emerged with flying colors. TThe Volvo City Safety, Mercedes Distronic Plus, and Honda CMBS use radar systems to mitigate and prevent low speed collisions – which, as a category, make up 75% of all motor accidents.
Matthew Avery, Thatcham Research Manager said: “They will make a major impact on the number of slow speed accidents – in Britain and across the World. Thatcham believes that if manufacturers embrace the new systems and fit them as standard – more than 125,000 injuries will be prevented each year in Britain alone.”
The Volvo City Safety uses laser radar, or LIDAR, to track the distance and speed of the car in front of the driver. The windscreen mounted device renews its calculations 50 times a second, pre-charging the brakes to avoid potential collisions before drivers can even sense the danger.
The system is active at speeds of up to 18.7 mph and has a range of up to six meters in front of the car. If a driver fails to activate the brakes before an imminent collision, the City Safety system automatically stops the car, and even steers it out of harms way. If the failsafe activates while the car is traveling below 10 mph, the collision should be averted completely, and at a speed of below 20 mph, the impact will be reduced by 50%.
The Volvo City Safety will be fitted as standard to the XC60, which is available this November.
Like the City Safety, the Mercedes Distronic Plus uses a form of radar to maintain safe distance from neighbouring cars. However, the two radars on the Distronic Plus are linked to the car’s cruise control, adding an extra level of autonomy to the system. The Distronic Plus operates at speeds of up to 200 km/h, keeping your car in sync with traffic whether it be stop-and-start gridlock or long stretches of freeway.
The short-range 24 gigahertz radar sweeps a fan-shaped 80-degree pattern with 30 meters of range, while the 77 gigahertz radar sweeps a nine-degree pattern at a far longer range – combined, the radars cover 145 meters of road.
As an added safety precautions, the Distronic Plus incorporates the Brake Assist Plus, and the PRE-SAFE system.
The Brake Assist Plus functions in a similar way to the City Safety, monitoring the distance between cars and adjusting brake pressure to avoid collisions. In tests conducted by Mercedes, the integrated system reduced rear collisions in heavy city traffic by 75%.
PRE-SAFE works with Distronic Plus to tighten front seat belts and alter seat positioning in the moments preceding a collision. The system also closes sunroofs if it senses an impending rollover, and closes side windows to better support air bags.
The Mercedes Distronic Plus is currently available on some S-class models. S-Class is also the first model of Mercedes to incorporate Night View Assist, which uses infra-red light projectors to create a high-resolution video display of up to 150 meters of upcoming road in the instrument cluster.
The Honda CMBS also uses radar to calculate the distance and speed of the vehicle in front, sending visual and audible warnings to the driver and automatically applying the brakes if a collision is imminent. Like the PRE-SAFE, CMBS E-Pretensioners tighten seat belts to lessen the chance of injury resulting from collisions.
The CMBS operates only when the car is traveling at greater speeds than 9.3 mph, and when the speed difference between it and the vehicle in front exceeds 9.3 mph. This is to minimise annoyances the system might cause when a driver wishes to, say, park a car.
The CMBS operates in three stages. If the distance between the two vehicles tightens, it sounds a buzzer and displays a BRAKE message on the car display. If that is ignored, it will automatically apply light braking combined with light tugs on the driver’s seat belt. The final stage occurs when the system perceives a collision as imminent – it tightens the seat belts and applies full brakes.
While all three systems use radar technology to create impressive, and effective, collision prevention systems, they are also vulnerable to radar’s weaknesses. Weather conditions like fog and rain can undermine its effectiveness, and dirt can obscure the sensor.
Car safety technology, for all its good intentions, has also been theorized to have negative psychological consequences. Some studies have shown that drivers will increase risk-taking behavior as a result of a perception of increased safety. In our opinion it would be nice to think that people aren't that stupid! The car companies themselves, and Thatcham, point to the obvious fact their technologies are most effective when used with an alert, responsible driver.
Overall, the attitude toward radar based safety tech is optimistic, with car manufacturers predicting that the systems can be further refined to detect other collisions, including those with pedestrians. Matthew Avery said “These systems are a massive breakthrough for keeping motorists safe. Vehicle manufacturers should be congratulated for developing and introducing this technology which is significant for the safety of all UK road users.”
At the very least, they might help bring automobile insurance rates down – and that’s a vision of the future that’s almost as appealing as flying cars.