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Focus: Transportation Management

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From SCDigest's On-Target E-Magazine

June 21, 2011


Logistics News: Hours of Service Now Down to Battle of the Academics


FMCSA Releases Several Studies Supportive of HOS Changes, but ATA Research Expert Questions Results


SCDigest Editorial Staff


It's hard to know how the Federal Motor Carrier Safety Association (FMSCA) is going to come down with regard to potential changes to current Hours of Service Rules (see Proposed New Hours of Service Rules a Lump of Coal in Trucking Industry Stocking, ATA Says), but now we having dueling academics, with the FMSCA seeming to show signs it favors the proposed changes based on the research it sponsored.

SCDigest Says:

Knipling said he had "fundamental criticisms" of the Penn State study, concluding that the sample of drivers, trucks and crashes, as well as minimal attention paid to other factors in crashes, rendered the study of little value.
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In May, the FMSCA introduced into its "docket," an area of additional information about the proposed changes to the regulations, three academic studies supporting the case that reduce hours of service might have a significant impact on truck driver safety.

For example, it posted a study titled "Hours of Service and Driver Fatigue: Driver Characteristics Research," which was written by Paul P. Jovanis, Kun-Feng Wu, and Chen Chen of the Larson Transportation Institution at Penn State University, under contract from the FMSCA. (The full study is available here.)

The report says that the research was needed because of the "the inconsistent and sometimes contradictory findings of truck driver safety research" to date.

This Larson study used a methodology that tried to identify the probability of a crash for a driver after a certain amount of time driving given no crashes until that time. It relied on carrier-supplied driver logs for periods of 1–2 weeks prior to each crash and compared those results to a random sample (two drivers) of non-crash-involved drivers selected from the same company, terminal, and month, using statistical methods. Data from 2004–05 and 2010 were collected from a total of 1,564 drivers, with the researchers determining by some means it was OK to combine the data even with six years of separation.

Data were separated into truckload (TL) and less-than-truckload (LTL) analyses because previous research indicated differences in crash contributing factors for each segment.

"Considering all the data, there is a consistent increase in crash odds as driving time increases," the report abstract says. "LTL drivers experienced increased crash odds after the 6th hour of driving. Breaks from driving reduced crash odds. In particular, a second break reduced crash odds by 32 percent for TL drivers and 51 percent for LTL drivers. There was, however, an increase in crash odds associated with the return to work after a recovery period of 34 hours or more."

More specifically, the researchers found on the LTL side that there is "a strong and consistent pattern of increases in crash odds as driving time increases."

It found that the highest odds are in the 11th hour, and that there is a consistent increase after the 5th hour through the 11th hour.

It then turns into statistical gobbledygook.

"Specifically, the increase in odds is statistically significant in the 6th hour," the report says.

"The crash odds are significantly higher here than all previous hours, except the 5th. The 7th hour is significantly higher than first 5, but not the 6th; the 8th hour is significantly higher than hours 1–6 and barely higher than the 7th hour; the 9th hour is higher than hours 1–7 and not higher than the 8th hour; the 10th hour is higher than hours 1–8 and not higher than hour 9; and the 11th hour is higher than all previous hours."

Got it?

(Transportation Management Article Continued Below)




The study found little correlation between overall increases in hours driven in crashes for truckload drivers, however, until the 11th hour, as shown in the chart below. However, the data for the 11th hour was sparse, leading the researchers to say more study is needed. Needless to say, however, this data on the surface seems supportive of the proposal to reduce driving time limits from 11 hours currently to 10.



Source: Hours of Service and Driver Fatigue: Driver Characteristics Research

There was also some seemingly odd data in the results, such as that starting to drive during the morning without a prior 34-hour recovery period had by far the lowest change of an accident ensuing during the trip. Starting at night after the recovery period resulted in a 58-64% increase in accident probability. Go figure.

The FMSCA also entered into the docket a study with relatively similar findings from the Virginia Tech Transportation Institute, and another on Florida transit bus drivers that found accidents increased for them over the course of driving time.

ATA Expert Fights Back

The American Trucking Associations (ATA),which can be fairly said to be leading the charge against changes to HOS among the many organizations that have come out against the proposals, fired back against what it saw as flaws in the methodologies and conclusions coming out of this research.

In a letter to FMCSA administrator Ann Ferro two weeks ago, Dr. Ronald Knipling, the former head of FMCSA’s research division and the first American to receive the prestigious Order of Merit from the International Road Transport Union for his work on truck safety, called into question the validity of the studies. Interestingly, Knipling is currently Senior Research Scientist and Senior Transportation Fellow with the Virginia Tech Transportation Institute, the organization that authored one of the reports entered into the docket.

Knipling said he had “fundamental criticisms” of the Penn State study, concluding that the sample of drivers, trucks and crashes, as well as minimal attention paid to other factors in crashes, rendered the study of little value.

“It would be erroneous and unwarranted to accept Penn State’s principal findings and conclusions without extensive re-analysis, internal validation, and external replication,” Knipling added.

The faults Knipling finds in the Penn State study include:

  • There was no description of crash characteristics (other than their associated work schedules) provided
  • There was no distillation of the crash dataset to exclude non-preventable crashes
  • The researchers did not perform validation tests of study conclusions via disaggregation of the crash dataset by prominent fatigue-related factors; i.e., single-vehicle vs. multi-vehicle crashes and other crash characteristics
  • Inadequate attention was paid to time-of-day as a "looming confound"
  • The study employed an inter-subject design rather than intra-subject design [We think this means the study should have looked at a how given driver performed within different hours of driving, not just between drivers]
  • There were a relatively small number of 11th hour crashes and exposure hours
  • The study sample may be unrepresentative due to apparent inclusion of truck tractors not equipped with sleeper berths

Knipling also says the Virginia Tech study is lacking and that “more probing and self challenging analyses must be performed before [the] study[‘s] findings can be accepted as sound science.”

Knipling also submitted a summary of his own work on the subject, where he has found that fatigue related to lack of prior sleep, being awake for more than 16 hours and early morning driving was associated with many single vehicle truck crashes, while fatigue “related only to driving and work schedules (e.g., as prescribed by daily hours-of-service rules) were not. This non-association was confirmed by several different types of analyses.”

The FMSCA is expected to make its decision soon. Public comment on the proposed changes ended in March of this year.

What do you think of these battling studies? Does the FMSCA research seem to tip the hand of which way it is going to rule? How big will the impact be if the proposed changes are enacted? Let us know your thoughts at the Feedback button below.


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