The driver, 51-year-old Ernest Carter Jr., died in the wreck along with four young passengers.
Texas Department of Public Safety investigators used cellular telephone records to determine that Mr. Carter had apparently been up all night before the fatal bus trip. DPS Lt. Ben Valdez said Mr. Carter falsified the medical card required for his certification because his eyesight failed to meet federal standards.
The conclusions are documented in the department's final report on the June 24 crash near Terrell on Interstate 20.
"Put it all together and you have a tragedy waiting to happen," Lt. Valdez said.
According to the report, which was issued today, Mr. Carter had also used cocaine and valium on the morning of the crash.
Mr. Carter was a contract driver for Discovery Tours. The company was subcontracted by Green's Transportation, which had been hired by Metro Church of Garland to take about 80 young people to a church camp in Louisiana. Green's provided a second church bus.
About 30 miles into the trip, Mr. Carter's bus crashed into a bridge pillar, killing four youths and injuring three dozen others. The bus had illegal tags.
Mr. Valdez said an investigation into the bus' operation by Wisconsin-based Discovery Tours was ongoing.
Mr. Carter had a valid commercial driver's license despite a record of traffic violations dating back nearly 17 years. State records show that Mr. Carter was convicted of drunken driving in 1985 in California and in 1994 in Dallas County.
Mr. Carter's license was suspended in California in 1989 and in Texas in 1997.