The Federal Motor Carrier Safety Administration (FMCSA) today finalized rules requiring that any passengers riding in a commercial truck wear seat belts while the vehicles are operating on public roads in interstate commerce.

The rules, first proposed last December, mandate that carriers and drivers be responsible for ensuring that any passengers in a rig be buckled up. The rule takes effect Aug. 8.

"Seat belts save lives-period," said Transportation Secretary Anthony Foxx in a statement. "Whether you're a driver or passenger, in a personal vehicle or large truck, the simple act of wearing a safety belt significantly reduces the risk of fatality in a crash."

A 2014 FMCSA driver survey found that passengers in commercial vehicles wore seat belts at a 73-percent rate, compared with an 84-percent wear rate for commercial drivers. Federal rules have long required all commercial drivers to wear seat belts.

In 2014, 37 passengers traveling unrestrained in cabs of large trucks were killed in roadway crashes, according to FMCSA, citing data from the National Highway Traffic Safety Administration (NHTSA). About one-third of the total fatalities were occupants who were ejected from the truck cab, FMCSA said, again citing NHTSA data.

FMCSA oversees motor carriers, freight brokers, domestic freight forwarders, and passenger-bus and motor-coach companies.