EAST LIBERTY, Ohio — The safety benefits of electronic stability control (ESC) were brought to life in a thrilling test ride on a school bus here in late September.
Blue Bird dealers and trade journalists climbed aboard and held on tight as the bus — with outriggers extending from the side — was driven through a series of maneuvers with and without the aid of ESC.
Blue Bird and Bendix conducted the demonstration at the Transportation Research Center in East Liberty, Ohio, about 50 miles outside of Columbus.
Blue Bird introduced factory-installed ESC as an option for its All American and Vision school buses in December of last year. The Bendix system, branded ESP, is an anti-lock brake system-based technology that works to enhance stability and control during under- and over-steer driving situations.
The technology is designed to mitigate rollovers and loss of control, including slides and skids. It uses sensors throughout the chassis of the bus to monitor various vehicle parameters: the yaw rate, steering angle, brake pressure and lateral acceleration. To help keep the bus stable, the system can apply the brakes separately on the four wheels in a specific pattern.
Michael Uszak, account manager for Bendix, said that while the ESP system can enhance safety in hazardous situations, it doesn't take any responsibility away from the driver.
"The driver is always responsible for control of the vehicle," Uszak said. "The driver should intervene before the system does."
But out on a test lot for the demonstration, attendees got to experience the full effect of the ESP system intervening.
Scott Szymczak, an engineer for Bendix, drove the bus through several turning maneuvers, first with ESP off, then with ESP on.
For example, when the bus took a sharp turn too fast with no stability control assistance, Szymczak had to work hard at the wheel to keep the bus on the correct path (designated by cones) and passengers had to hold on to the seats in front of them.
With ESP activated and the bus going into the turn at the same speed — about 35 mph — the system recognized the risk and intervened by applying the brakes and de-throttling the engine. The result was that the bus automatically slowed down to about 25 mph, and the turn became more controlled and comfortable for the driver and passengers.
Another part of the demonstration was on a slippery surface — an epoxy-coated area that was sprayed with water. In this case, the ESP system helped keep the bus from sliding out of its intended path while turning on the wet roadway.
While stability control technology is new to the school bus market, it has more experience on the road in trucks and other vehicles. More than 300,000 commercial vehicles in the U.S., Canada and Mexico are equipped with Bendix ESP.
In June, the National Highway Traffic Safety Administration finalized a rulemaking that requires electronic stability control systems on heavy trucks and some large buses, such as motorcoaches, but school buses are exempt.