The nation’s economy depends on it, but shipping by truck comes with a heavy price, in terms of both environmental damage and damage to the highway infrastructure.
Trucks rely almost exclusively on oil-based fuels. They represent the second-largest source of global oil demand, following passenger cars. Road freight is the largest source of global diesel demand, at around half of the global total.
Although heavy trucks are efficient for hauling cargo, their high annual mileage means that they consume about one-fifth of global oil demand — equal to the oil production of the U.S. and Canada combined and to the oil needs of the entire industry sector.
Since 2000, trucking has outpaced all other economic sectors in oil demand growth. While passenger car oil use has begun to plateau or decline in many industrialized countries, oil use by trucking continues to rise. Without mitigating policy efforts, oil demand from road freight vehicles is set to rise by five million barrels per day by 2050. Emerging and developing countries in Asia, in particular China and India, account for about 90 percent of the net increase in road freight oil demand.
With this high dependency on oil come environmental issues. Globally, more than one-third of transport-related carbon dioxide emissions, and 7 percent of total energy-related carbon dioxide, come from freight transport by road.
What can be done? The International Energy Agency report advocates a number of marginal improvements to the operation of trucks, projecting a potential efficiency improvement of as much as 40 percent. Systemic improvements to road freight operations can improve the on-road efficiency of trucking operations. Global positioning systems to optimize truck routing, driver training, and the use of on-board, real-time feedback devices could be helpful.
Existing trucks can benefit from aerodynamic retrofits and low-rolling-resistance tires. For new trucks, technologies exist for reducing idling, using lightweight materials, and improvements to truck engines, transmissions, and drivetrains. Using alternative fuels — natural gas, biofuels, electricity, and hydrogen — could also help reduce carbon dioxide and air pollutant emissions.
Tightening fuel economy standards and expanding their geographic coverage could accelerate fuel economy improvements. Standards could be supported by differentiated vehicle taxation favoring efficient trucks.
However, beyond its environmental impact, trucking presents another major problem. According to the General Accounting Office study “Excessive Truck Weight: An Expensive Burden We Can No Longer Afford,” road damage caused by a single fully loaded five-axle rig weighing 80,000 pounds — the interstate legal maximum — causes as much damage to a highway as 9,600 cars because of its much greater weight. Trucks, like all things on wheels, only touch the road on relatively small surfaces where the tires meet the pavement. The result is huge pressure gouging a depression along the path the tires roll over, sometimes even cracking the pavement.
Road damage is related to the fourth power of the relative loads, in other words, if one vehicle weighs 1,500 pounds per axle and another 3,000 pounds per axle, the road damage caused by the heavier vehicle is not twice as much, but 2 to the fourth power (2x2x2x2) or 16 times as much damage as the lighter vehicle. The table illustrates:
So an 80,000-pound 18-wheeler full of cargo, 20 times heavier than a 4,000-pound passenger car, causes 160,000 times more road damage than the car.
The Government Accountability Office’s conclusion is that “heavy and overweight trucks are a major cause of highway deterioration.” Because of the disproportionate impact of heavier loads, even a small percentage of overweight trucks significantly decreases the useful lifespan of U.S. highways. Increasing a truck’s weight from 80,000-90,000 pounds results in 42 percent greater road wear. Pavements designed to last 20 years wear out in seven.
In this era of increasing gridlock, deteriorating highways and bridges, and growing pressure on highway budgets, the sensible way to lengthen the lifespan of roads is to shift long-distance cargo from truck to rail, with trucks transporting only containerized freight locally, to and from the nearest rail hub.
Now is the time to shift. Waiting until the situation becomes dire will ensure panic fixes leading to unending, expensive “emergency” corrective measures.
(Paul Kando is a co-founder of the Midcoast Green Collaborative, which works to promote environmental protection and economic development via energy conservation. For more information, go to midcoastgreencollaborative.org.)