Civil Engineer Karim Chatti

Oct. 13, 2020

MSU expert asked: Do Heavy Trucks Damage Our Roads?

MSU Civil Engineer Karim Chatti is among the experts who helped Inside Science explore the old question: How Much Damage Do Heavy Trucks Do to Our Roads?

Professor Karim Chatti said two-axle cars do little damage to pavement.
Professor Karim Chatti said two-axle cars do little damage to pavement.

In an article published Oct. 12, 2020, Chatti and others explained an old rule of thumb for comparing the amount of pavement damage caused by vehicles with different weights, in terms of axle loads.

The simple equation was based on a series of experiments from the 1950s still serves as the rule of thumb for estimating road damage.

Consider a standard sedan with two axles and a total weight of four tons. Assuming an even distribution, each of its axles would bear the weight of two tons. Now consider a semitruck with eight axles and a weight of 40 tons -- each of its axles would weigh five tons. The relative damage done by each axle of the truck can be calculated with the following equation, and comes out to 40 times the damage done by each axel of the sedan.

Professor Karim Chatti
Professor Karim Chatti

Considering that the truck has eight axles and the sedan has two, the relative damage caused by the entire semitruck would be 40 x (8/2) -- 160 times that of the sedan.

“The damage due to cars, for practical purposes, when we are designing pavements, is basically zero. It’s not actually zero, but it’s so much smaller -- orders of magnitude smaller -- that we don’t even bother with them,” said Karim Chatti, a civil engineer from Michigan State University in East Lansing.

Read more at Inside Science.