Safety is the beginning of every conversation about transportation policy changes. When it comes to modernizing Department of Transportation regulations for the length of twin, or double, “pup trailers,” safety should be a paramount issue. The evidence is in; a modest five foot extension on each trailer would improve stability, reduce the number of collisions and enhance safety for all highway users.
More than a dozen years ago, a special report from the Transportation Research Board of the National Academies recommended a new regulatory system to permit twin 33s based on objective performance standards like safety.
A new look at length limits on twin trailers — while keeping weight restrictions in place — is an idea whose time has come. It can provide immediate improvements to handling and stability on the roads and relieve congestion across the country.
Current federal law limits twin trailers to 28 feet in length. In isolated pockets around the country, there are states that have been grandfathered and allow longer 33 foot trailers to operate in tandem. In these areas twin 33s have covered millions of miles in a safe and efficient manner. Studies from analysts at the University of Michigan and the U.S. Department of Transportation show the extended wheelbase of the twin 33s make it more stable than twin 28s.
A 2011 study comparing the features of twin 28s and twin 33s also examined the academic literature on safety studies and concluded, “the literature surveyed showed that longer vehicles tend to have better vehicle dynamic characteristics and in general they have better safety performance.”
Beyond the academic studies, real-world experience in Florida and South Dakota demonstrate the safety performance of twin 33s. Millions of miles are driven with the twin 33 configuration and there are no discernable negative safety effects. To the contrary, compared to the current federal rule limiting twin trailers to 28 feet, twin 33s would move more freight and as a result an estimated 6.6 million truck trips would be avoided annually.
Prime beneficiaries of this effect would be regular users of the highway system including passenger vehicle drivers. To imagine the scale of congestion relief available by adding only five feet onto twin trailers, if one truck with twin trailers was lined up for each of the 6.6 million avoided trips, the line of trucks would stretch around the entire equator 3.71 times.
According to a 2013 analysis by the American Society of Civil Engineers, 42 percent of America’s major highways remain congested. Everyday experience demonstrates that congestion leads to increased anxiety and frustration on the roads. Some drivers exhibit significant degradation of decision making after experiencing congestion. Using formulas from the Federal Motor Carrier Safety Administration, the proposal to leave weight restrictions unchanged and to extend twin trailers five feet would result in an estimated 912 fewer highway accidents.
Fewer accidents are better for our professional drivers, better for our customers and better for all highway users. It is a proposal worth backing.