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ATA now supports longer and/or heavier trucks

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Here's something to bandy about.... http://www.aset-safety.org/study/study.html ....from "Americans for Safe and Efficient Transportation". Don't really know right off hand if they are pro-rail or pro-truck, or just whatever. But they do point to a few specific USDOT studies that show the benefit of allowing an increase in the Interstate Highway System GVW limit from 80,000 to 97,000. Going by prescribed axle group limits of 12k per steering axle, 34k per tandem, and 51k per tridem, and then projecting those prescribed limits in moving from a 5 axle 80k GVW to a 6 axle 97k GVW, they get the following: "Allowing higher weights for a variety of current truck configurations, including the 97,000 pound scenario is anticipated to result in an overall reduction in heavy commercial truck vehicle miles traveled (VMT) of 11 percent in the year 2000. Five-axle tractor semitrailer VMT declines by 70 percent, decreasing from 83,895 million miles to 24,997 million miles. Shifting the freight to a six-axle tractor semitrailer results in only a 3 percent increase in VMT for these vehicles, going from 6,049 million miles to 6,246 million miles." Like I said, allowing higher GVW would result in less overall truck traffic on the highways. "Savings in pavement restoration costs were largest under the North American Trade Scenario. An 11 percent decrease in VMT resulted in pavement restoration costs over 20 years of $2,447 million for a 97,000 pound vehicle scenario. The 70 percent reduction in VMT also results in predictions of much lower load equivalency factors (LEF). LEF’s ratings are essentially multipliers of the pavement wear of an 18,000 pound single-axle load. Accordingly, the LEF's for a 97,000 pound semitrailer load with a 51,000 pound tridem are 4.1 (front-axle), 8.4 (rear-axle), and 9.2 (tridem axle) for a six-axle semitrailer combination, versus 5.7, 9.3, and 10.3 for the five-axle semitrailer combination." Meaning overall pavement maintenance costs go down relative to total gross tonnage moving over the highways. "US DOT acknowledges that VMT and safety are tied closely together. In other words, a change from a 80,000 pound five-axle semitrailer to a 97,000 pound six-axle semitrailer would result in fewer accidents (approximately 11% fewer if the VMT model is maintained throughout the study). Heavier vehicles are not inherently more prone to instability or roll-over, rather payload distribution is the most critical factor in controlling rollovers. Driver operational characteristics such as travel speed around curves, the “tightness” of the curve, etc… are also important factors. Braking performance is admitted to not be particularly influenced by changes in vehicle sizes and weights, assuming that the required number of axles and brakes are added as the vehicles weight increases and the vehicle's brakes are well-maintained and functional. The requirement that antilock braking systems (ABS) be fitted to all new tractors and trailers is expected to enhance vehicle stability and control. Some incremental diminishments can be expected as truck weights are increased, but the greater concern in braking ability relates to longer combination vehicles." Meaning safety is not comprimised in shifting to higher GVW for trucks. "A six percent decrease in fuel use would be achieved by transition to the 97,000 pound weight limit. Truck VMT in urban areas would decrease by more than 5 billion miles, resulting in a substantial decrease in air pollution control costs for these areas. Noise costs increase marginally due to the number of additional tires (approximately 15%) used and the consequence of larger loads on increased engine noise." Meaning higher GVW are better for the environment. "Shippers converting to the use of six-axle 97,000 pound semitrailers would experience significant transportation savings. Truck shippers changing to higher GVW’s would save $13,277 million per year. Rail shippers changing from rail to truck would save $1,233 million per year. " Meaning domestic producers would be better able to compete with overseas imports. Also, note that the potential shift from rail to truck is small compared to the intramodal shift. It is my contention that most of that shift would occur in shortline and branchline corridors, where competition between trucks and rail is a reality (unlike the mainline corridors). Enjoy.
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