Three months after releasing a summary of its findings, the National Transportation Safety Board released its full final report Wednesday on a car crash that killed four Yale students on Jan. 17, 2003.

Travelling back from a Delta Kappa Epsilon fraternity event in New York City, Kyle Burnat ’05, Andrew Dwyer ’05, Sean Fenton ’04 and Nicholas Grass ’05 were killed after their vehicle collided with the trailer of a truck that had hit and broken through the median barrier on Interstate 95 minutes before the crash. The NTSB’s final report concluded that slippery road conditions caused by rain, snow and excessive speed caused the truck driver to lose control of his vehicle, according to the Associated Press. The report also found that a lack of highway lighting and the Connecticut Department of Transportation’s use of a mixture of sand and salt — which is less effective but cheaper than pure salt — contributed to the accident.

NTSB representatives could not be reached for comment Wednesday night.

Five other Yale students were seriously injured in the crash. Fenton, who was driving the 1999 Chevrolet Tahoe carrying the students, may have been tired and distracted by an earlier accident that had occurred on the same road, the report said. Two vehicles later collided with the jackknifed trailer, accounting for two of the 18 other accidents that occurred in the vicinity that night, the report said.

Test results revealed that neither of the drivers were intoxicated or under the influence of drugs, but some passengers in Fenton’s vehicle were not wearing seatbelts. The report repeated its recommendation that a more stringent law requiring all passengers in a car to use seatbelts be passed in Connecticut.

The summary report released three months ago concluded that the 32-inch barriers installed by the federal government were too short to prevent the 42,000 pound truck from crashing over the barriers. The driver of the truck told investigators he was distracted by flares set up on the highway to demarcate an accident that had occurred earlier.

Several DKE members declined to comment Wednesday night.

Jonathan Edwards College Master Gary Haller said the entire Yale community was affected by the crash.

“The whole institution was moved by it,” he said.