Wal-Mart trucks have been involved in 380 crashes in the past two years, federal data show. The crashes have caused nine deaths and 129 injuries. Wal-Mart has 6,200 trucks and 7,200 drivers, according to the Federal Motor Carrier Safety Administration, and they drove 667 million miles last year.
Roper's truck was equipped with a system designed to slow its speed and notify him of stopped traffic ahead, a company spokeswoman said. It's unknown if the system was working.
The National Transportation Safety Board is working with state police to look at any issues in the crash related to commercial trucking and limousine safety.
Federal regulations permit truck drivers to work up to 14 hours a day, with a maximum of 11 hours behind the wheel. Drivers must have at least 10 hours off between work shifts to sleep.
Wal-Mart said it believed Roper was operating within federal regulations.
"Safety is the absolute highest priority for Walmart," it said in an emailed statement.
But safety advocates said they hope the accident will help their case.
"This is part of a systemic problem of having tired people driving at night and driving large trucks," said Henry Jasny, vice president of Advocates for Highway and Auto Safety.
But Dave Osiecki, vice president of the American Trucking Association, said no regulations can prevent a driver from making "bad choices."
Morgan, a New York City native, was returning from a standup performance at Dover Downs Hotel & Casino in Delaware when the crash occurred. Six vehicles were involved in the pileup, but no one from the other cars was injured.
McNair, of Peekskill, New York, was a close friend and mentor to Morgan, Morgan's ex-wife told the New York Daily News.
Associated Press writers Joan Lowy in Washington, D.C., and Dee Ann Durbin in Detroit contributed to this story.