"OnGuard also has an adaptive cruise control mode, which the driver can engage or disengage at his own discretion," says Alan Korn, director of vehicle dynamics and controls for Meritor Wabco. "In this mode, OnGuard automatically attempts to maintain a safe distance behind the lead vehicle, accelerating or decelerating as needed,"
If the truck driver sets his cruise control at 60 mph and the lead vehicle is going 70 mph, the cruise control will go up to 60. However, if the lead vehicle decelerates to 50, the cruise control will match it with a 50 mph speed.
"It does this by the radar sensor realizing what the lead vehicle is doing and adjusting the speed by dethrottling the engine, applying the engine brake and the foundation brakes."
According to Korn, a truck needs to have a stability control system already in place in order for it to be capable of automatically applying foundation brakes.
A drawback to adaptive cruise control systems is the fact that these systems are blind to stationary vehicles that may be stopped in a queue on the highway or vehicles that may have broken down in front of the truck. If a driver's attention is taken away before he notices the queue, the system will not warn him of the situation. This is why ACC is in no way a substitute for an alert driver.
"It's important to note that forward crash warnings systems do detect stationary vehicles, but the ACC does not, it tunes them out," says the University of Michigan's Sweatman.
Gary Strausbaugh, vice president of transportation for Mennel Milling Co. in Fostoria, OH, maintains a fleet of 55 units. His company uses the Eaton Vorad Forward Collision Avoidance System on many of the units and says the system is practically maintenance free.
"If it's on cruise, the system will actually defuel the truck and hit the Jake brake if the driver is drowsy and the lead vehicle slows. It's not a substitute for a driverless truck though."
Strausbaugh says drivers with ACC systems have a general complaint about loss of power if someone suddenly cuts them off on the highway. If the truck has a jake brake, it will cut the fuel and hit the jake, which means the truck takes a few minutes to get back up to its cruise speed.
Prime Inc. has also had the Vorad system installed on its fleet for a number of years to great effect. Though Prime's Lacy says that driver acceptance is another issue.
"Some of our drivers have learned to disregard the signals. Sometimes they'll even disable it--all they really have to do is cover up the antennae."
The Human Equation
"These systems have limits," explains Fred Andersky, marketing manager for Bendix Commercial Vehicle Systems LLC, Elyria, OH. The company supplies active safety technologies, air brake charging and control systems and components for trucks. It is in the process of launching its own adaptive cruise control system. "We sometimes use the term 'collision mitigation' because it's not going to help you avoid every accident."
According to Andersky, truck drivers need to understand that forward collision avoidance systems are not a replacement for their own good driving practices or the fleet's driver training efforts. "The fact is, we can slow a vehicle down, but we can't make it stop on a dime. We need the driver to be doing his job as well."
Bendix has been building its new adaptive cruise control system for trucks on top of the Bendix Full Stability System. Thanks to the stability system's yaw sensor, this interface actually provides more options for a driver to avoid a crash situation.
"The system might engage with the breaks, but the driver realizes he's not going to stop in time and while we're taking the energy out of the way, he realizes the right or left lane is clear, so he swerves to avoid the car ahead of him," says Andersky.
By having the collision avoidance system built into the stability system, Andersky says the driver can make the swerving maneuver and not worry about the possibility of getting into a loss of control situation that might result in a rollover.
In general, lane forward crash warning systems are extremely effective at helping to warn drivers of imminent crashes and allowing them to reduce their vehicles' forward momentum so that if they cannot avoid a crash, they can at least strike the vehicle in front of them with less energy.