The new safety assist technologies on the 2014 Mercedes-Benz E-Class sedans, wagons, coupes, and cabriolets provide another level of semi-autonomous driving via automatic braking and other functions to help prevent a collision or mitigate the severity of an impending accident.
Sensors and the associated algorithms, forward radar, as well as new rear radar are the template for the various driver assist technologies, but the primary enabler for additional semi-autonomous driving functionality is the stereo multipurpose camera.
Unlike the "mono" camera used on the 2013 E-Class, the stereo camera provides a three-dimensional, forward view of up to 55 yd (50 m) as well as an overall range of up to 550 yd (503 m). The stereo camera via image processing algorithms can identify other vehicles, motorcycles, bicyclists, animals, and pedestrians.
Located on the windshield near the rearview mirror, the stereo camera adds a new dimension to brake assist capabilities.
The BAS (Brake Assist System) Plus with Cross Traffic Assist system for 2014 calculates if an intersection collision is possible based on the speed of travel as well as the direction and the position of another vehicle. If a crash threat exists, an audible alert occurs.
“Once you touch the brake, the networked system will automatically apply the correct amount of brake pressure to stop the vehicle before the collision. That’s important because a driver’s normal tendency is to not brake hard enough, fast enough,” David Larsen, E-Class Product Manager, said during an interview with SAE Magazines at an E-Class media ride-and-drive event in Ann Arbor, MI, on June 12.
Depending on vehicle speed, road conditions, and other factors, the E-Class can be stopped before a collision occurs or the automatic braking will minimize the severity of the crash.
“At 2.6 s before impact, you’ll get an audible warning. At 1.6 s before impact, the vehicle will apply 40% of braking capacity. And at 0.6 s before impact, the vehicle will apply 100% of braking as long as the front-seat occupants are wearing seatbelts,” said Larsen, noting that autonomous braking scenarios include cross traffic incidents.
Active Lane Keeping Assist adds functionality in 2014.
“The stereo camera can recognize an oncoming vehicle and if your vehicle starts to lane drift, the car will initiate single-side braking to pull the car back into the lane. So if the car is drifting to the left, the brakes on the right side of the vehicle will be applied to ‘steer’ the vehicle to the right. In this case it’s not steering by the front wheels, but steering by braking,” explained Larsen.
The stereo camera also provides a vital assist for the new Distronic Plus with Steering Assist.
Rather than just "seeing" the immediate lead car—which was the case in 2013—the forward radar along with the stereo camera enable the vehicle to monitor two vehicles ahead of the E-Class car. “This is an example of the car beginning to anticipate traffic patterns,” Larsen said, noting this system helps keep the vehicle centered in its lane while semi-autonomously following inline traffic.
The 2014 application of Enhanced Attention Assist adds visual cues of green, yellow, and red bars in the instrument cluster to warn of drowsy driving, and the driver can now tune the system’s sensitivity level.
“When the S-Class arrives in U.S. dealerships in September, the Enhanced Attention Assist system will gain another feature. So rather than just having audible and visual alerts, the navigation system will offer you the distance and the route to the nearest rest stop,” Larsen said.
Enhanced Attention Assist does not use the stereo camera.
According to Bart Herring, Mercedes-Benz USA’s General Manager of Product Management, while other systems use cameras to read lane markings or track eye movements, the standard Enhanced Attention Assist system relies on the steering-wheel-angle sensor.
“The act of getting drowsy involves some weaving inside the lane, and that’s what the steering wheel angle sensor in our car measures. There are very telltale movements that we all make when we get tired, including very minute steering wheel corrections. The system looks for those movements as well as sensor data to provide information about your level of activity in the car,” Herring said.
Other optimized driver assist technologies include Pre-Safe Plus with Rear-End Collision Protection. The system prepares occupants for an impending rear-end collision by tightening seatbelts, activating the headrest, as well as closing the windows and sunroof. Once the vehicle is stopped, the brakes are locked.
Larsen said that the brake locking feature is new for 2014. “What that does is prevent a secondary impact—either hitting a car in front of you or being pushed out into the intersection where you could be hit by traffic,” Larsen said.
The 2014 E-Class sedan and wagon U.S.-launched in April. By September, all 15 variants of the 9th generation E-Class will be in dealer showrooms.