Travel on the Interstate Highway System is inherently safer than travel on other road types.  Vehicles generally travel at the same speeds, in the same direction, on separated travel lanes with no at-grade intersections - greatly reducing the likelihood of conflicts with other vehicles.  Each year, heavy trucks are involved in approximately 4,000 fatal crashes, the majority of which are collisions with other motor vehicles.  It stands to reason then that carriers whose trucks travel almost exclusively on Interstates would be “safer” than those that travel more frequently on non-Interstate highways.

A number of years ago I had the opportunity to test this hypothesis while going one step further.  We identified the descriptive characteristics of the carriers involved in fatal crashes that occurred on Interstate and non-Interstate roadway networks and found profound differences.

We were able to link carrier descriptive information from FMCSA’s MCS-50T form with combination-unit truck fatal crash data in North Carolina and Virginia from 2005-2009. Not surprisingly, in both states, there were more fatal crashes off Interstate highways than on the Interstates.  Furthermore, the characteristics of the carriers involved in crashes on the two types of roads were markedly different.

Off the Interstates, the fleet size of the carriers was smaller, more of them were domiciled in the state in which the crash occurred.  More of them were private and exempt carriers (as opposed to TL or LTL for-hire carriers) and, in many cases, the crash occurred very close to the carrier’s place of business.  For crashes on the Interstates, the carriers tended to be larger, were more likely to be a for-hire carrier located in other states, and had traveled greater distances from their business location before the crash occurred. The crash pattern differences, on both roadway types, of small carriers (10 or fewer vehicles operated) were the same but more pronounced compared to the patterns associated with carriers of all fleet sizes. A separate study of single-unit truck fatal crashes in Virginia for the same time period found the same but stronger associations.

The results suggest that small local/regional carriers face higher risks and safety challenges simply due to the highway environments in which they operate. Accordingly, new ways to assist them – other than enforcement related programs, should be explored. Many people assume that small carriers don’t have good safety management programs, but part of the challenges they face could simply be the roads they travel.  The results also highlight the distinctly different use patterns of combination-unit and single-unit trucks and, therefore, the need to consider them separately, not as the single group of large trucks.  

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