Results are in from the Commercial Vehicle Safety Alliance's (CVSA) unannounced Brake Safety Day inspections in May, and out of nearly 10,000 vehicles inspected, ultimately, more than one out of five were taken off the road.

The enforcement effort was part of CVSA's Operation Airbrake Program and took place May 3. A total of 9,524 roadside inspections were conducted in 33 U.S. states and 10 Canadian provinces, including 8,140 in the former and 1,384 up north.

Overall, though, nearly four out of five — 79% — of all commercial motor vehicles inspected passed inspection, with no critical item vehicle violations found. The remaining 21% of the total, which amounts to 1,989 commercial trucks and buses, were placed out of service for violations of some kind.

The primary target of the surprise inspection day, which was to identify out-of-adjustment brakes and brake system/ antilock braking system (ABS) violations, netted 1,146 vehicles placed out of service. It was 12% of the inspections, all told, that turned up brake-related critical item vehicle violations.

CVSA provided a closer look regarding ABS compliance as well, based on jurisdictions' surveys of that specifically. Of 4,635 trucks with air brakes identified as requiring ABS, 8% — 391 — had ABS violations. Trailer-related violations were more frequent: of 3,222 trailers requiring ABS, 487 had ABS violations, or 15% overall.

Of the 723 trucks inspected with hydraulic brakes requiring ABS, somewhat fewer had problems with those systems. Some 6% of those (41) had ABS violations, according to CVSA, and among the 57 buses inspected that required ABS, six — or 11% — had ABS violations.

"Improperly installed or poorly maintained brake systems can reduce the braking capability and increase stopping distance of trucks and buses, which poses a serious risk to driver and public safety," CVSA stated regarding the brake safety effort.

That's it for this year's unannounced enforcement events, but another Brake Safety Day is set to take place Thurs., Sept. 7.