At the request of the
Western Governors’ Association, the Federal Highway Administration has assessed
the impact of lifting the current freeze on longer combination vehicles in 13
states that currently allow the larger vehicles. At this time, the agency does
not appear likely to change the current rule.
The report, Western Uniformity Scenario Analysis,
addresses the impact of expanded operations assuming that weights would be
limited only by the federal axle load limits and the federal bridge formula,
with a maximum gross vehicle weight of 129,000 pounds and a length of two
The report finds both positive and negative impacts.
It estimates that total truck traffic would decrease by 25 percent
in the region, primarily in the long-haul trucking sector. Forecasts for total
truck vehicle miles traveled in 2010 would drop from 18.8 billion to a little
more than 14 billion.
The most dramatic change would be seen in a 76 percent drop in
travel by conventional five-axle tractor-trailers. And less than one-tenth of 1
percent of rail traffic would be expected to divert to LCVs.
However, the report also finds that the changes in the scenario
would affect long-term pavement and bridge costs, and necessitate interchange
and other design improvements to accommodate larger trucks. Pavement costs might
actually decline by 4 percent, according to the analysis, because of reduced
However, bridge improvement costs are projected to double as
states address bridges overstressed by additional weight. Additional costs are
also anticipated for improvements to geometric designs to accommodate the
The FHWA report says safety data is inadequate to fully determine
potential impacts upon vehicle safety, and adds that impacts on traffic
operations are also an issue.
The largest benefit would be reduced shipper costs. If fully
implemented in each state, the report estimates that the scenario could save
shippers some $2 billion a year, a savings of almost 4 percent in the region.
The report maintains that few Western states charge fees that
cover the kind of infrastructure costs that would be associated with LCV
operations, and recommends that this issue be addressed, so that the increased
costs are not passed on to other highway users.
The FHWA concludes, “Strong
support from elected officials of states within the region for a change in
truck size and weight limits has not been evident to date, and there is no
compelling federal interest in promoting changes that are not strongly
supported by the affected states.”