ALEXANDRIA, Va. --- A new study found that the U.S. trucking industry has improved truck safety, making strides in both safety belt use and compliance with hazardous materials regulations. The 2007 truck safety Roadcheck was conducted throughout North America by the Commercial Vehicle Safety Alliance (CVSA). On the other hand, study results also showed slight increases in the number of drivers and vehicles parked for work-and-rest violations, as law enforcement officials continue to do a better job of targeting drivers with previous violations. American Trucking Associations (ATA) President and CEO Bill Graves praised CVSA for a successful Roadcheck. "ATA supports the removal of unsafe trucks from the road," he said. "CVSA continues to become better at targeting those drivers and vehicles that should be out of operation. We appreciate CVSA's annual Roadcheck effort, which helps ensure that education and enforcement are having a positive impact on safety." The number of vehicles, including trucks and buses, placed out of service represented 21.5 percent of the vehicles inspected. This compared with 21.7 percent in 2006. The number of safety belt violations during the June 5-7 enforcement blitz decreased significantly to 829 in 2007 from 1,223 a year earlier. The number of hazardous materials trucks placed out of service also declined to 17.7 percent from 18.2 percent in 2006. The number of trucks parked for brake defects also dropped. Drivers placed out of service for non-compliance with hours-of-service rules increased slightly, as 4.9 percent of all inspections resulted in a driver being placed out of service for hours-of-service violations, up from 4.5 percent in 2006. The Roadcheck inspections were not performed at random. Trucks and drivers were targeted for inspection based upon the safety record or previous inspection records of the motor carrier or the driver, or upon the observation skills of the trained inspectors. The inspectors use a computerized Inspection Selection System (ISS) by entering the vehicle, company and driver identifying information into the computer. The ISS then gives the inspector one of three results: "inspect," "inspection optional" or "don't inspect."