For trucking safety directors, understanding crash risk and how to mitigate it is the name of the game. There is a super long list of risk factors to consider. One that’s often overlooked—time of day–was the subject of a recent Virginia Tech Transportation Institute research project and report. The research was groundbreaking considering the amount of data analyzed (over 134,000 drivers, over nearly 22 million log days, and 36,000 crashes) as well as being one of the only studies on the topic to use exposure data to test common assertions about the crash risk of daytime vs. nighttime driving.

The results showed 6 am and 11 pm to be, by far, the riskiest hours of driving, showing big spikes in all crash types during this time. The findings support the longstanding industry practice of having overnight drivers stop for a break between 5 and 6 am. It is, after all, the beginning of rush hour traffic and the end of their shift. The more surprising finding is that the riskiest hour to drive, by a fair margin, is 11 pm, which was measured as twice as dangerous compared to many other hours. This finding strongly suggests to carriers with overnight operations that enacting countermeasures between 10 pm and midnight may bear some real safety fruit. Following the data improves safety.

If your company already requires countermeasures in the 10 pm to midnight timeframe, we’d love to hear what they are and your experience. Share your practices with STC Vice President P. Sean Garney at