Effects of Raising Load Limits on Pavements and Bridges in Indiana

Abstract

Indiana's present weight limits for trucks arc 18,000 Jbs. on a single axle, 32,000 lbs. on a tandem axle and 73,280 lbs. gross vehicle weight. Many states have increased their weight limits to 20,000 lbs. on a single axle, 34,000 lbs. on a tandem axle and with gross limits of 80,000 lbs. This study was conducted to determine possible economic impacts on maintenance of Indiana highways and bridges if weight limits were to be increased in Indiana. Extensive use was made in this research of work reported by other investigators. The road life records of the Indiana State Highway Commission were searched and pavement sections were evaluated using these data coupled with truck weight information from the weight stations, soil information and performance data on file in the JHRP offices.

Effect of Truck Weight on Bridge Network Costs

“…In 1979, a study was conducted by Yoder et al (1979) to investigate the impact of a GVW limit increase from 326 kN (73.28 kips) to 356 kN (80 kips) for Indiana DOT. Both bridges and pavements were covered.…”

Amount of Travel and Fuel Sales Attributable to Out-of-State Vehicles on Indiana Highways

“…The average fleet fuel efficiency rates for 1979 for automobiles, single unit trucks and combination trucks were obtained from a recent report (5) The 1979 auto fleet fuel efficiency was 14.7 miles per gallon (mpg) while the corresponding rates for single unit trucks and combination trucks were 10.75 mpg and 6.04 mpg, respectively. The percentage of combination trucks in the truck fleet on Indiana highways has been estimated to be 53% (8) Therefore, a weighted average truck fleet fuel efficiency rate was estimated as shown below. This weighted average truck fleet fuel efficiency value was then applied in estimating fuel consumption by trucks.…”