The Loudoun County Sheriff's Office conducted spot safety inspections on 18 trucks Friday and ordered half of them off the road for violations, officials said.

A total of 53 safety violations were discovered and 14 summons issued during inspections at Belmont Ridge Road and Ryan Road, the Sheriff's Office said. Most of the citations were for defective equipment -- such as insufficient tire tread -- load violations and driver violations, such as no medical certification or no commercial motor vehicle operator's license.

Last year, the Sheriff's Office removed from the roads three of every five trucks inspected and cited 6,215 safety violations. This year, truck safety inspectors have removed 57 percent of the vehicles they checked.

Among the tools used in the inspections are two thermal imaging units to detect heat that results from braking action. The Sheriff's Office said it believes Loudoun was the first local jurisdiction in Virginia to acquire this technology for truck safety enforcement, through a grant from the Federal Motor Carrier Safety Administration.

In the units first few months of use, 88 percent of the trucks detected by the equipment have been removed from service and 443 violations were discovered.

"The absence of heat means the brakes are not functioning" properly, said Sheriff Stephen O. Simpson.

"Malfunctioning or inoperative brakes on trucks poses a serious hazard to other motorists," Simpson added, "and this equipment allows our truck inspectors to quickly screen and identify suspected offenders, stop them for further inspection and remove them from service if confirmed violations warrant it."

Lt. Vernon Foster orders a commercial truck off the road for alleged safety violations.