“Electronic stability systems were found to provide substantial safety benefits. Assuming that all existing 5-axle tractor semitrailers operating on U.S. roads were fitted with the technologies as they address rollover-relevant crashes, the expected annual reductions are 106 fatal injuries and 4,384 injuries.” –From the Safety Benefits of Stability Control Systems For Tractor-Semitrailers study released today by the National Highway Traffic Safety Administration
The days of electronic stability systems being merely optional technology for tractor-trailer fleets might well be numbered following a new study released today by the National Highway Traffic Safety Administration (NHTSA).
Conducted by the University of Michigan Transportation Research Institute (UMTRI) under a cooperative agreement between NHTSA and Meritor WABCO, the study examines the performance of electronic stability control (ESC) systems and roll stability control (RSC) systems for tractor-trailers.
Despite its clunky title (Safety Benefits of Stability Control Systems For Tractor-Semitrailers), this report contains some powerful data – the kind of information that can set the wheels in motion on a regulatory or even legislative level in order to improve highway safety.
Now, NHTSA admits its study of electronic stability systems on tractor-trailers comes with a few major caveats – the largest being that it’s a largely “theoretical” analysis done with post-crash data. In short, they didn’t measure the impact of stability control technology in actual crashes; instead, they looked at how such systems MIGHT have performed has they been installed on tractor-trailers involved in major accidents. Still, even with that being said, the findings are extremely interesting:
• Assuming that all existing 5-axle tractor-trailers operating on U.S. roads were fitted with RSC, the expected annual rollover relevant safety benefit is a reduction of 3,489 crashes, 106 fatalities, and 4,384 injuries.
• Alternatively, assuming that all existing 5-axle tractor-trailers operating on U.S. roads were fitted with ESC, the expected annual combined rollover and directional (yaw) instability relevant safety benefit is a reduction of 4,659 crashes, 126 fatalities, and 5,909 injuries.
• Because ESC addresses both rollover and yaw instability crashes and it is more effective in mitigating rollover crashes (through additional braking capabilities over RSC), the net annual expected benefit for an ESC system was found to be greater than for RSC.
• The study found that ESC provided more overall safety benefit than RSC, though the difference between the estimated effectiveness of RSC and ESC varied among crash scenarios.
• Assuming ESC was fitted to all tractor-trailers, savings from rollovers prevented by ESC are estimated at $1.527 billion annually, and from LOC [loss-of-control] crashes prevented at $210 million annually, for a total of $1.738 billion annually.
• Assuming RSC was fitted to all tractor-semitrailers, savings from rollovers prevented at estimated at $1.409 billion annually, and from LOC crashes prevented at $47 million annually, for a total estimated benefit of $1.456 billion annually.
Again, though, despite these impressive findings, I still feel the study remains limited to a degree in terms of applying all of this to the real world because of its “theoretical” nature.
“The analysis of crash datasets proved challenging [as] identifying relevant LOC and rollover crashes within the national datasets proved a formidable task because the databases are developed for general use and this project required very precise definitions of LOC and rollover,” NHTSA noted in its report. “Relying on the general LOC or rollover categories captures a wide range of crashes, many of which have no relevance to the technology.”
Still, this study remains an important step forward in figuring out how technology can significantly boost highway safety. Just look at these numbers and you’ll know why that’s true: Although rollovers occur in only about 13% of heavy-truck fatal crashes, rollovers account for 50% of truck occupant fatalities, notes NHTSA.
Also, LOC and rollover crashes remain a major cause of fatalities and traffic tie-ups, resulting in millions of dollars of lost productivity and excess energy consumption each year – not to mention the emotional toll traffic injuries and deaths take as well, although you can’t put a dollar figure on them.
