The analysis by the American Transportation Research Institute, an arm of American Trucking Associations, found that RSC trucks had lower average crash rates than ESC trucks, with RSC being significantly less expensive than ESC.
The issue is significant in a proposed new rule by the National Highway Traffic Safety Administration that would mandate ESC on new tractors. The agency evaluated both technologies and found that the net benefit of ESC is greater than RSC.
Both systems perform a similar function: if sensors detect the risk of rollover or instability, the control module slows the vehicle by cutting back the throttle and applying the brakes automatically.
The difference is that RSC is triggered only when the system detects roll instability, which might occur when a truck is going too fast into a turn or maneuvers too quickly.
ESC reacts to both roll instability and yaw instability, such as a skid that could lead to a jackknife. In addition to slowing the vehicle to prevent a rollover, it applies the brakes on the wheel that needs to be slowed to counteract the skid.
The ATRI study reflects ATA's contention that, while it supports a stability control mandate, NHTSA should consider the diversity of operations in the industry.
As Ted Scott, director of engineering at ATA, put it, "One size does not fit all."
ESC may be more effective than RSC, but the difference is not enough to justify going with the ESC mandate, he said. "The point is that such a diverse industry needs standards that provide flexibility."
ATRI said it looked at crash and financial data for more than 135,000 trucks.
"Contrary to findings in several earlier studies, this analysis of operational data indicates that, for some fleets, RSC technology may be more effective, and cost-effective, at reducing rollover, jackknife and tow/stuck crashes than ESC technology," ATRI says in its report.
If these findings from this data sample turn out to be consistent with the industry as a whole, RSC would provide a greater benefit at lower cost than ESC, ATRI said. The Institute called for more research into the issue.
Comments on NHTSA's proposed rule are due August 21.
7/25/2012 NHTSA's Stability Control Proposal Gets First Public Airing
5/17/2012 NHTSA Proposes Stability Control Mandate