February 16, 2006
Since you asked
Trucks’ clearance is just fine
When traveling the freeways I see large semi-trucks going under the overpasses. It appears that they have only 2 or 3 inches of clearance. Is this because of the angle of sight? I know trucks
and overpasses have different heights, but what is the average clearance?
— Vic M., Rogue River
Appearances can be deceiving, Vic.
According to Oregon Department of Transportation District Manager John Vial, what looks to you like mere inches is actually a couple feet of clearance in most cases.
"It’s an optical illusion," says Vial.
Most semi-trucks have a maximum height of 13-14 feet. Any higher and the operator must carry a special permit, says Vial.
Conversely, the lowest bridge on Interstate 5 in our area is 16 feet 4 inches from the highway below it, he says.
Seventeen feet is the current federal standard for clearance on new bridges. ODOT requires an additional six inches of height on new bridges, Vial adds.
However, once one is off the interstate, there are all sorts of short-height bridges, Vial says. Hence the truck-free zones and height warnings one often sees posted on bridges crossing city
streets or smaller highways.
Another caveat to his "room to spare" comments is when mobile homes are taken via trailer to their new locations, says Vial.
"In that case, there are often only 3 or 4 inches’ clearance," says Vial.
Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to
youasked@mailtribune.com. We’re sorry, but the volume of questions received prevents us from answering all of them.
