|8.0 SUMMARY AND CONCLUSIONS
A test procedure was developed for evaluating the ability of heavy truck automatic traction control (ATC) to improve vehicle stability and control on slippery surfaces at highway speeds. ATC is an optional feature of ABS. At speeds above about 30 mph the ATC controls drive-axle wheel slip via engine speed control over a serial datlink (databus) between the ABS/ATC ECU and the engine ECU. At lower speeds the ATC controls engine speed and also applies the rear brakes to control differential wheel speed.
The test procedure developed was evaluated using two different vehicles, two different brands of ATC and two different serial datalinks (SAE J1922 and 1939). The procedure was able to discriminate between different ATC performance levels and did find deficiencies in one of the two vehicles tested. The problem appeared to be due to slow response from the engine on the older vehicle tested (1995 model engine) and occurred with both ATC systems evaluated.
ATC appears to have the potential to significantly improve vehicle stability and control on slippery surfaces at highway speeds. The later model vehicle tested (2000 model engine electronics) was able to negotiate curves on ice surfaces even with full throttle accelerations in a bobtail tractor configuration.
Due to the fact that ATC is highly integrated with the engine, ABS and pneumatic systems, retrofitting ATC to older vehicles is generally not practical.