Multiple security background checks and costly fees have caused the population of truck drivers with Transportation Security Administration hazardous materials endorsements to decline by roughly 1.2 million since 2004, a top American Trucking Associations official told a congressional subcommittee last week.

The Pipeline and Hazardous Materials Safety Administration said a new federal rule will expand the enforcement authority of federal regulators to conduct “enhanced inspections” and investigations of packaged hazardous materials.

Several trade groups told federal regulators that requiring more detailed information on applications for special permits to haul hazardous materials will not increase hazmat safety and will increase the paperwork burden on applicants.