Truck Crashes: Size Does Matter and Bigger Trucks May Be Getting a Bad Rap

June 6, 2013

Size apparently does matter in the area of truck crashes, and probably not the way you might think. The largest trucks on the road may be getting a bad rap from highway safety advocates based on faulty analysis of truck accident data.

Lumping medium-duty truck crash statistics with Class 7 and 8 accident data may be dragging down the safety gains made by heavy-duty truck fleets, according to research that investigated the most critical crash factors associated with different truck sizes and configurations.

The American Transportation Research Institute (ATRI) recently released research findings that investigated variations in safety trends across different classes of large trucks. The study separated and evaluated a decade of medium- and heavy-duty truck crash records and identified notable crash trends specific to each population.

Using an ATRI-designed "crash rate index," ATRI isolated specific variables such as vehicle type, crash location, and weather to determine the degree to which certain factors influenced crash trends for medium- and heavy-duty trucks. The analysis revealed noticeable differences in safety trends between different truck sizes, with medium-duty generally performing worse than heavy-duty trucks. In addition, the results indicated disparities between interstate and intrastate motor carriers.

Previously, research has examined safety trends based on a common industry definition of "large trucks" being all trucks with a gross vehicle weight rating greater than 10,000 pounds. However, within the generalized "large truck" category, important operational and functional distinctions exist between Class 3 through 6 medium duty trucks weighing 10,001 to 26,000 lbs. and Class 7and 8 heavy-duty trucks weighing more than 26,001 pounds, ATRI says.

To get a clearer picture of how the size of large trucks is reflected in crash trends, ATRI researchers investigated a decade (2000-2010) of Federal Motor Carrier Safety Administration (FMCSA) Motor Carrier Management Information System (MCMIS) crash data to examine large truck crash trends. The research team developed a methodology to separately examine medium-duty and heavy-duty truck crash trends

ATRI's trend analysis confirms that overall, large truck crash rates are decreasing;

however, the rate of this decline is slowed by contrary trends observed in the medium duty truck subgroup. As a result, large truck crash statistics understate the safety improvements realized by the heavy-duty truck population over the 10-year analysis period.

Furthermore, and perhaps more importantly, medium-duty truck crash rates are camouflaged by the improvement of overall large truck crash statistics, ATRI says. This, in turn, may result in researchers and policy makers overlooking certain truck populations for crash reduction opportunities.

The research team developed a methodology to separately examine medium-duty and heavy-duty truck crash trends based on a crash rate index (CRI). The CRI, which explored each group's crash trends compared to a baseline, showed distinct differences among heavy-duty and medium-duty truck crash trends.

As a result of the distinctions highlighted by ATRI's CRI analysis, the research team conducted further investigation to determine which crash attributes, such as road configuration or weather, contribute most to the disparities in crash trends for the two groups. The additional examination provides insight for targeting crash mitigation efforts based on truck gross vehicle weight ratings.

Based on their findings, the researchers say that developing and implementing medium duty truck-specific crash mitigation strategies would likely intensify the existing improvements in large truck safety. Specifically, the analysis revealed that:

  • Whereas Heavy Duty trucks have generally experienced a decline in CRI (-24.6% between 2000 and 2010), medium-duty trucks have seen an increase in the index (38.3% between 2000 and 2010).
  • Non-interstate carrier crashes exhibited a steep increase in CRI compared to interstate carriers, particularly among medium-duty truck crashes.
  • An increase in medium-duty truck crashes on roads with full access control in urban core counties were responsible for much of the increase in medium-duty truck CRI.
  • Adverse weather conditions had somewhat of an equalizing effect, reducing the differences between medium-duty and heavy-duty truck CRIs.
  • More data, such as driver citations and vehicle speed, is needed to determine the underlying crash causal factors.

"In order to continue to make progress in truck crash rates, we must improve our ability to target safety strategies across all segments of the industry," said Keith Klein, COO of Transport America. "This research will enhance our industry's ability to customize safety solutions."

"This research also points out that blending medium-duty crash statistics with heavy-duty crash statistics may unfairly drag down the safety gains made by heavy-duty truck fleets," said American Trucking Assns. President and CEO Bill Graves. "When it comes to truck safety, clearly one-size solutions do not fit all scenarios."

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