Larger Trucks More Efficient, Reduce Emissions, Study Says

By Sean McNally, Senior Reporter

This story appears in the April 14 print edition of Transport Topics. Click here to subscribe today.

The use of heavier trucks can be an effective way for the industry to reduce fuel consumption and emissions, a new study by the American Transportation Research Institute said.

“The estimated fuel efficiency improvements found in this study translate directly into equivalent percentage improvements . . . of CO2 emitted,” the report said.

“As we look for ways to reduce congestion and greenhouse gas emissions, without sacrificing the supply chain efficiencies that the trucking industry supports, higher productivity vehicles should be considered as a viable part of an overarching solution,” said Doug Duncan, president of FedEx Freight and ATRI chairman.

In 2006, American Trucking Associations voiced support of 97,000-pound, six-axle trucks, and last year, the federation included that stance in a package of environmental policies aimed at reducing the industry’s greenhouse gas emissions.

Meanwhile, some former opponents of raising size-and-weight limits are changing their positions, partly because of the fuel economy and emissions gains.

The Truckload Carriers Association has been opposed to any change in the size-and-weight limits, mainly over concerns that shippers would not compensate carriers for the extra capacity, but a former TCA chairman said he has changed his mind.

“I, for one, have a different opinion about this than I did even two years ago and I believe that we need to find a way to allow the operation of higher productivity vehicles,” said Jim O’Neal, president of O&S Trucking Inc. and immediate past chairman of TCA.

“I, personally, as O&S Trucking, think we have to look at increasing, at least the weight of these trailers for environmental reasons, economic reasons and [congestion] reasons. There’s no question in my mind,” O’Neal said.

However, other opponents of increasing truck sizes said the environmental rationale was just an attempt to muddle the debate.

“We are familiar with the trucking industry’s effort to take the debate over longer, heavier trucks, which is a safety issue, and turn it into muddier issue pitting environmental concerns against safety,” said Robert Shull, deputy director for auto safety and regulatory policy for Public Citizen. “We haven’t heard any carbon-savings figures that would be substantial enough to turn anyone’s head, much less spin the whole debate around.”

Todd Spencer, executive vice president of the Owner-Operator Independent Drivers Association, said his members were “not fans of bigger and heavier [trucks] simply because we represent the people that actually have to pilot that equipment around and we don’t see the economic benefit.”

Spencer said any environmental benefits paled compared with the group’s safety and business concerns over larger trucks.

ATRI’s study looked at the performance of six different vehicle combinations: a five-axle tractor-trailer, a five-axle double, a six-axle tractor-trailer, a Rocky Mountain double, a triple and a turnpike double.

“Operating vehicles at higher [weights] may require the use of larger engines which, combined with the additional weight, decreases fuel economy on a miles-per-gallon basis,” the report said, but the smaller number of trips would more than offset that disadvantage.

For example, the five-axle tractor trailer and the double hauling 80,000 pounds both averaged

5.4 mpg in the study, while the six-axle truck weighing 97,000 pounds averaged 4.9 mpg. The triple, according to ATRI, got 3.8 mpg when hauling 140,000 pounds.

Despite reduction in fuel economy per single trip, fuel and emissions savings would add up over multiple trips.

“For diesel engines, approximately 22.2 pounds of CO2 is emitted into the atmosphere for each gallon of diesel fuel burned,” ATRI said.

The report said that moving a 1,000-ton shipment 500 miles would consume 3,889 gallons of fuel and take 42 trips if hauled by a standard five-axle truck weighing 80,000 pounds. However, the same shipment sent using a Rocky Mountain double weighing 120,000 pounds would burn 3,215 gallons of fuel, making just 27 trips.

“This decrease in fuel consumption equates to an equivalent percentage reduction in CO2 emissions, with nearly 7.5 fewer tons of CO2 being emitted into the atmosphere,” the report said.