WASHINGTON, D.C. — Driving after a break appears to be one of the greatest traffic risks for commercial vehicle drivers, according to a recent study. The study, conducted by the Virginia Tech Transportation Institute (VITT) and funded by the Federal Motor Carrier Safety Administration (FMCSA), indicates that there is a potential for a “safety critical event,” not only on the first day, but also within the first hour according to previous research funded by the same agency which shows a “trend” between the two studies, according to one of the researchers.

The most recent VTTI “naturalist truck driving study” suggests that driving after a two-day break is a potentially risky period for a “safety critical event” (SCE) which could be a “crash, a near-crash or a crash relevant conflict,” according to the study terms. Researchers don’t know why that first day after a break is so potentially risky for a SCE, but they now have a great deal of data that will allow them to further analyze that type of activity and how it might be contributing to the truck drivers crash or conflict.

“That gives us a clue, or some information, that something is happening during their off-duty period,” says Myra Blanco, a researcher with VTTI, which undertook the research for the FMCSA, the findings of which were discussed publicly this week. “They’re potentially carrying over what they do, during their vacation time their off duty time that may be potentially affecting their driving performance. This is consistent with the results of a previous study that was performed at VTTI, where drivers were evaluated in a similar manner, when they were sleeping in the sleeper berths of the tractors.”

The previous study was funded by the FMSCA and announced in April. That study was undertaken to determine the safety of driving a truck over a period of one to 11 hours, in relation to the new CMV hours of service regulations. Researchers discovered that the first hour of driving is the most potentially risky for a crash by far. The higher crash percentage in the first hour of driving was a major finding that was relevant to an assessment of the existing federal Hours-of-Service (HoS) regulations, in an examination of the 11-hour driving period for truck safety. That study was in response to public criticism over the safety aspect of a regulatory increase of driving from 10 to 11 hours, after the regulations changed in 2005.
As for a potential relationship between the two FMCSA studies, Blanco seems to think there is a trend. Since the researchers have a wide collection of data associated with the naturalistic truck driver study, Blanco indicates the researchers can now analyze the on- and off-duty behaviour of drivers, which might determine why there is a potential for a SCE after a break. “It might be something else related to their work, that is not related to their work schedule, or what they do at work, that might be affecting that first day and first hour,” she says.
The FMCSA indicates that it is also considering the apparent relationship, between the two studies. “We are reviewing both studies at this time,” says Duane J. DeBruyne, spokesman for the FMCSA.

In the naturalistic truck driving study, the average sleep pattern before a SCE was 6.6 hours, during a six-month truck driving study, that involved four fleet companies with 100 Class A commercial vehicle drivers, and nine trucks that were fitted out with instrumented monitors, both sensor and video. Naturalistic data was collected by studying driver behaviour and performance in a naturalistic environment, such as light vehicle commute to and from work, and truck drivers operating on revenue producing run. The research study was valued for offering high validity and low control, officials said.

Safety critical events were identified with “sample event triggers” that included: longitudinal acceleration, time-to-collision, swerve, lane deviations, critical incident button, and analyst-identified information that was also validated with video review. The safety critical events were classified as three types: crash, near-crash and crash-relevant conflict (less severe evasive manoeuvre as compared to a near-crash). The study observed 2,899 safety-critical events, with 13 crashes (and eight tire strikes, 61 near-crashes, 1,594 crash relevant conflicts, 1,215 unintentional lane deviations, and 16 illegal manoeuvres. The drivers were classified in three categories: shorthaul (less than 100 miles); medium (100 to 500 miles); and longhaul (over 500 miles).

Part of the research included countermeasures for CMV drivers, such as to increase driver attention to forward visual scene; improve general driver situation awareness and/or proactive/defensive driving and increased driver alertness. For the five crash occurrences, the countermeasures were to improve general driver situation awareness and/or proactive/defensive driving, and increase and/or improve driver use of mirrors or provide better information from mirrors.