Hours of Service of Drivers, 49978-50073 [05-16498]

Agencies

• Federal Motor Carrier Safety Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 70, Number 164 (Thursday, August 25, 2005)]
[Rules and Regulations]
[Pages 49978-50073]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-16498]



[[Page 49977]]

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Part II





Department of Transportation





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Federal Motor Carrier Safety Administration



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49 CFR Parts 385, 390, and 395



Hours of Service of Drivers; Final Rule

Federal Register / Vol. 70, No. 164 / Thursday, August 25, 2005 / 
Rules and Regulations

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DEPARTMENT OF TRANSPORTATION

Federal Motor Carrier Safety Administration

49 CFR Parts 385, 390 and 395

[Docket No. FMCSA-2004-19608; formerly FMCSA-1997-2350]
RIN-2126-AA90


Hours of Service of Drivers

AGENCY: Federal Motor Carrier Safety Administration (FMCSA), DOT.

ACTION: Final rule.

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SUMMARY: FMCSA is publishing today its final rule governing hours of 
service for commercial motor vehicle drivers, following its Notice of 
Proposed Rulemaking published January 24, 2005. The rule addresses 
requirements for driving, duty, and off-duty time; a recovery period, 
sleeper berth, and new requirements for short-haul drivers. The hours-
of-service regulations published on April 28, 2003, were vacated by the 
U.S. Court of Appeals for the District of Columbia Circuit on July 16, 
2004. Congress subsequently provided, through the Surface 
Transportation Extension Act of 2004, that the 2003 regulations will 
remain in effect until the effective date of a new final rule 
addressing the issues raised by the court or September 30, 2005, 
whichever occurs first. Today's rule meets that requirement.

DATES: This rule is effective October 1, 2005.

FOR FURTHER INFORMATION CONTACT: Tom Yager, Chief, Driver and Carrier 
Operations Division, Office of Bus and Truck Standards and Operations 
(MC-PSD), Federal Motor Carrier Safety Administration, 400 Seventh 
Street. S.W., Washington, DC 20590. Phone 202-366-4009, E-mail 
MCPSD@fmcsa.dot.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

A. Legal Basis for the Rulemaking
B. Background Information
C. Executive Summary
D. Research Review Process
E. Driver Health
F. Driver Fatigue
G. Current and Future FMCSA Research
H. Crash Data
I. Operational Data
J. Comments to Docket and FMCSA Responses
    J.1. Sleep Loss
    J.2. Exposure to Environmental Stressors
    J.3. Workplace Injuries and Fatalities
    J.4. Lifestyle Choices
    J.5. Driving Time
    J.6. Duty Tour
    J.7. Off-Duty Time
    J.8. The 34-Hour Restart and 60/70-Hour Rules
    J.9. Sleeper-Berth Use
    J.10. Regulation of Short-Haul Operations
    J.11. Combined Effects
    J.12. Effective and Implementation Dates
    J.13. Electronic On-Board Recording Devices
    J.14. Other Provisions
    J.15. Legal Issues
K. Rulemaking Analyses and Notices
    K.1. Executive Order 12866 (Regulatory Planning and Review) and 
DOT Regulatory Policies and Procedures
    K.2. Regulatory Flexibility Act
    K.3. Unfunded Mandates Reform Act of 1995
    K.4. National Environmental Policy Act
    K.5. Paperwork Reduction Act
    K.6. Executive Order 13211 (Energy Supply, Distribution, or Use)
    K.7. Executive Order 12898 (Environmental Justice)
    K.8. Executive Order 13045 (Protection of Children)
    K.9. Executive Order 12988 (Civil Justice Reform)
    K.10. Executive Order 12630 (Taking of Private Property)
    K.11. Executive Order 13132 (Federalism)
    K.12. Executive Order 12372 (Intergovernmental Review)
L. List of References

Table of Abbreviations

AHAS Advocates for Highway and Auto Safety
AMI Acute Myocardial Infarction
AMSA American Moving and Storage Association
ANPRM Advance Notice of Proposed Rulemaking
APA Administrative Procedure Act
ATA American Trucking Associations
BAC Blood Alcohol Content
BLS U.S. Bureau of Labor Statistics
BMI Body Mass Index
CATF Clean Air Task Force
CDL Commercial Drivers License
CEQ Council on Environmental Quality
CFR Code of Federal Regulations
CHP California Highway Patrol
CMV Commercial Motor Vehicle
CRASH Citizens for Reliable and Safe Highways
CRMCA Colorado Ready Mixed Concrete Association
CTC Corporate Transportation Coalition
CVD Cardiovascular Disease
CVSA Commercial Vehicle Safety Alliance
dBA Decibels Adjusted
DE Diesel Exhaust
DOT Department of Transportation
EA Environmental Assessment
ECMT European Conference of Ministers of Transport
EEI Edison Electric Institute
EOBR Electronic On-Board Recorder
EPA U.S. Environmental Protection Agency
FARS Fatality Analysis Reporting System
FHWA Federal Highway Administration
FMCSA Federal Motor Carrier Safety Administration
FMCSR Federal Motor Carrier Safety Regulations
FMP Fatigue Management Program
FONSI Finding of No Significant Impact
FR Federal Register
GVWR Gross Vehicle Weight Rating
HEI Health Effects Institute
HOS Hours of Service
IBT International Brotherhood of Teamsters
ICC Interstate Commerce Commission
ICCTA ICC Termination Act of 1995
IIHS Insurance Institute for Highway Safety
IRP International Registration Plan
ISO International Standards Organization
LBP Lower Back Pain
LH Long Haul
LR Long Regional
LTL Less-Than-Truckload
MCMIS Motor Carrier Management Information System
MCSAP Motor Carrier Safety Assistance Program
MFCA Motor Freight Carriers Association
MPH Miles per Hour
MTA Minnesota Trucking Association
NACA National Armored Car Association
NAICS North American Industrial Classification System
NEPA National Environmental Policy Act
NHTSA National Highway Traffic Safety Administration
NIH National Institutes of Health
NIOSH National Institute for Occupational Safety and Health
NITL National Industrial Transportation League
NPRM Notice of Proposed Rulemaking
NPTC National Private Truck Council
NRMCA National Ready Mixed Concrete Association
NSSGA National Stone, Sand, and Gravel Association
NTSB National Transportation Safety Board
OMB Office of Management and Budget
OOIDA Owner-Operator Independent Drivers Association
OOS Out-of -Service
OSHA U.S. Occupational Safety and Health Administration
OTR Over-the-Road
PATT Parents Against Tired Truckers
PM Particulate Matter
PMC PubMed Central
PRA Paperwork Reduction Act of 1995
PVT Psychomotor Vigilance Test
RIA Regulatory Impact Analysis
RMA Risk Management Association
R&T Research and Technology
RODS Records of Duty Status
SBA Small Business Administration
SH Short Haul
SR Short Regional
STAA Surface Transportation Assistance Act
TCA Truckload Carriers Association
TIFA Trucks Involved in Fatal Accidents
TL Truckload
TOT Time-on-Task
TRB Transportation Research Board
UMTRI University of Michigan Transportation Research Institute
UPS United Parcel Service
USV Utility Service Vehicle
VIUS Vehicle Inventory and Use Survey
VMT Vehicle Miles Traveled
VSL Value of a Statistical Life
VTTI Virginia Tech Transportation Institute
WBV Whole Body Vibration

[[Page 49979]]

A. Legal Basis for the Rulemaking

    This rule is based on the authority of the Motor Carrier Act of 
1935 and the Motor Carrier Safety Act of 1984.
    The Motor Carrier Act of 1935 provides that ``The Secretary of 
Transportation may prescribe requirements for--(1) qualifications and 
maximum hours of service of employees of, and safety of operation and 
equipment of, a motor carrier; and (2) qualifications and maximum hours 
of service of employees of, and standards of equipment of, a motor 
private carrier, when needed to promote safety of operation'' [49 
U.S.C. 31502(b)].
    The hours-of-service regulations adopted today deal directly with 
the ``maximum hours of service of employees of * * * a motor carrier 
[49 U.S.C. 31502(b)(1)] and the ``maximum hours of service of employees 
of * * * a motor private carrier'' [49 U.S.C. 31502(b)(2)]. The 
adoption and enforcement of such rules was specifically authorized by 
the Motor Carrier Act of 1935. This rule rests squarely on that 
authority.
    The Motor Carrier Safety Act of 1984 provides concurrent authority 
to regulate drivers, motor carriers, and vehicle equipment. It requires 
the Secretary of Transportation to ``prescribe regulations on 
commercial motor vehicle safety. The regulations shall prescribe 
minimum safety standards for commercial motor vehicles.'' Although this 
authority is very broad, the Act also includes specific requirements: 
``At a minimum, the regulations shall ensure that--(1) Commercial motor 
vehicles are maintained, equipped, loaded, and operated safely; (2) the 
responsibilities imposed on operators of commercial motor vehicles do 
not impair their ability to operate the vehicles safely; (3) the 
physical condition of operators of commercial motor vehicles is 
adequate to enable them to operate the vehicles safely; and (4) the 
operation of commercial motor vehicles does not have a deleterious 
effect on the physical condition of the operators'' [49 U.S.C. 
31136(a)].
    This rule is based on the authority of the 1984 Act and addresses 
the specific mandates of 49 U.S.C. 31136(a)(2), (3), and (4). Section 
31136(a)(1) of 49 U.S.C. deals almost entirely with the mechanical 
condition of commercial motor vehicles (CMVs), a subject not included 
in this rulemaking. The phrase ``operated safely'' in paragraph (a)(1) 
refers primarily to the safe operation of the vehicle's equipment, but 
to the extent it encompasses safe driving, this rule also addresses 
that mandate.
    Before prescribing any regulations, FMCSA must also consider their 
``costs and benefits'' [49 U.S.C. 31136(c)(2)(A) and 31502(d)]. Those 
factors are also discussed later.

B. Background Information

B.1. History of the Hours-of-Service Rule

    The Interstate Commerce Commission (ICC) promulgated the first 
Federal hours-of-service regulations (HOS) in the late 1930s. The rules 
were based on the Motor Carrier Act of 1935. The regulations remained 
largely unchanged from 1940 until 2003, except for an important 
amendment in 1962. Prior to 1962, driver hours-of-service regulations 
were based on a 24-hour period from noon to noon or midnight to 
midnight. A driver could be on duty no more than 15 hours in a 24-
consecutive-hour period. In 1962, among other rule changes, the 24-hour 
cycle was removed and replaced by minimum off-duty periods. A driver 
could ``restart'' the calculation of his or her driving and on-duty 
limitations after any period of 8 or more hours off duty.
    Section 408 of the ICC Termination Act of 1995 (ICCTA) (Pub. L. 
104-88, 109 Stat. 803, at 958) required the Federal Highway 
Administration (FHWA) to conduct rulemaking ``dealing with a variety of 
fatigue-related issues pertaining to commercial motor vehicle safety.'' 
In response, FHWA published an advance notice of proposed rulemaking 
(ANPRM) on November 5, 1996 (61 FR 57252). FMCSA was established as a 
separate Agency on January 1, 2000. At that time, responsibility to 
promulgate CMV regulations was transferred from FHWA to FMCSA, which 
published an hours-of-service Notice of Proposed Rulemaking (NPRM) on 
May 2, 2000 (65 FR 25540) and a final rule on April 28, 2003 (68 FR 
22456). Technical amendments to the final rule were published on 
September 30, 2003 (68 FR 56208). Motor carriers and drivers were 
required to comply with the final rule on January 4, 2004.
    FMCSA's 2003 rule did not change any hours-of-service requirements 
for motor carriers and drivers operating passenger-carrying vehicles. 
They were required to continue complying with the hours-of-service 
rules existing before the 2003 rule (see 68 FR 22461-22462). Changes in 
hours-of-service provisions in the new rule applied only to motor 
carriers and drivers operating property-carrying vehicles. Compared to 
the previous regulations, the 2003 rule: (1) Required drivers to take 
10, instead of 8, consecutive hours off-duty (except when using sleeper 
berths); (2) retained the prior prohibition on driving after 60 hours 
on duty in 7 days or 70 hours in 8 days; (3) increased allowable 
driving time from 10 to 11 hours in any one duty period; and (4) 
replaced the so-called 15-hour rule (which prohibited drivers from 
driving after being on duty more than 15 hours, not including 
intervening off-duty time) with a 14-hour rule (which prohibited 
driving after the 14th hour after the driver came on duty, with no 
extensions for off-duty time). Note that the 15-hour limit had been 
cumulative--so it could be interspersed with off-duty time--while the 
non-extendable 14-hour limit was consecutive. Additionally, FMCSA 
allowed drivers to ``restart'' the calculations for the 60- and 70-hour 
limits by taking 34 consecutive hours off duty. Based on the data and 
research available at the time, FMCSA was convinced that these new 
rules constituted a significant improvement in the hours-of-service 
regulations, compared to the rules they replaced, by providing drivers 
with better opportunities to obtain off-duty time offering daily 
restorative sleep, thereby reducing the incidence of crashes wholly or 
partially attributable to drowsiness or fatigue.
    On June 12, 2003, Public Citizen, Citizens for Reliable and Safe 
Highways (CRASH) and Parents Against Tired Truckers (PATT) filed a 
petition to review the new hours-of-service rule with the United States 
Court of Appeals for the District of Columbia Circuit (D.C. Circuit). 
On July 16, 2004, the D.C. Circuit issued an opinion holding that the 
rule was arbitrary and capricious because the Agency failed to consider 
the impact of the rules on the health of drivers, as required by 49 
U.S.C. 31136(a)(4). Public Citizen et al. v. Federal Motor Carrier 
Safety Administration, 374 F.3d 1209, at 1216. The D.C. Circuit noted, 
however, that neither Public Citizen nor the court was ``suggest[ing] 
that the statute requires the agency to protect driver health to the 
exclusion of those other factors [i.e., the costs and benefits of the 
rule], only that the agency must consider it.'' Id. at 1217 (emphasis 
in original). Although FMCSA argued that the effect of driver health on 
vehicle safety had permeated the entire rulemaking process, the court 
said that driver health and vehicle safety were distinct factors that 
must be considered separately.
    In dicta the court also stated that: (1) FMCSA's justification for 
increasing allowable driving time from 10 to 11 hours might be legally 
inadequate because the Agency failed to show how additional off-duty 
time compensated for more driving time, and especially

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because it failed to discuss the effects of the 34-hour recovery 
provision; (2) splitting off-duty time in a sleeper berth into periods 
of less than 10 hours was probably arbitrary and capricious, because 
FMCSA itself asserted that drivers need 8 hours of uninterrupted sleep; 
(3) failing to collect and analyze data on the costs and benefits of 
requiring electronic on-board recording devices (EOBRs) probably 
violated section 408 of the ICC Termination Act, which requires FMCSA 
to ``deal with'' EOBRs; and (4) the Agency failed to address or justify 
the additional on-duty and driving hours allowed by the 34-hour 
recovery provision.
    On September 1, 2004 (69 FR 53386), FMCSA published an ANPRM 
requesting information about factors the Agency should consider in 
developing performance specifications for EOBRs. As the Agency said in 
the preamble to that document, ``FMCSA is attempting to evaluate the 
suitability of EOBRs to demonstrate compliance with the enforcement of 
the hours-of-service regulations, which in turn will have major 
implications for the welfare of drivers and the safe operation of 
commercial motor vehicles.'' The ANPRM asked for comments and 
information, both on technical questions relating to EOBRs, and on the 
potential costs and benefits of such devices. The EOBR rulemaking has 
been and will remain separate from this hours-of-service rulemaking. 
(For additional discussion of EOBRs, see Section J.13.)
    On September 30, 2004, the President signed the Surface 
Transportation Extension Act of 2004, Part V (Public Law 108-310, 118 
Stat. 1144). Section 7(f) of the Act provides that ``[t]he hours-of-
service regulations applicable to property-carrying commercial drivers 
contained in the Final Rule published on April 28, 2003 (68 FR 22456-
22517), as amended on September 30, 2003 (68 FR 56208-56212), and made 
applicable to motor carriers and drivers on January 4, 2004, shall be 
in effect until the earlier of--(1) the effective date of a new final 
rule addressing the issues raised by the July 16, 2004, decision of the 
United States Court of Appeals for the District of Columbia in Public 
Citizen, et al. v. Federal Motor Carrier Safety Administration (No. 03-
1165); or (2) September 30, 2005.'' (118 Stat. at 1154).

B.2. Notice of Proposed Rulemaking (January 24, 2005)

    FMCSA published an NPRM on January 24, 2005 (70 FR 3339) to 
reconsider the 2003 rule and determine what changes might be necessary 
to correct the deficiencies identified by the court. The Agency used 
the 2003 rule as a proposal for the purpose of soliciting public 
comments, but also announced that ``[t]his rulemaking is necessary to 
develop hours-of-service regulations to replace those vacated by the 
Court'' (70 FR 3342). The NPRM asked a series of questions on driver 
health, sleep loss and deprivation, driving time, sleeper berths, and 
other subjects; the answers are discussed later. While awaiting the 
submission and review of docket comments, the Agency pursued a research 
program to identify relevant studies on the same issues; the results of 
that effort are also described in later sections of the preamble.

C. Executive Summary

    Today's rule requires all drivers of property-carrying commercial 
motor vehicles (CMVs) in interstate commerce to take at least 10 
consecutive hours off duty before driving, limits driving time to 11 
consecutive hours within a 14-hour, non-extendable window after coming 
on duty, and prohibits driving after the driver has been on duty 60 
hours in 7 consecutive days, or 70 hours in 8 consecutive days. Drivers 
may restart the 60- or 70-hour ``clock'' by taking 34 consecutive hours 
off duty.
    These provisions are the same as those of FMCSA's 2003 final rule 
that was vacated by the U.S. Court of Appeals for the D.C. Circuit and 
then reinstated by Congress for the duration of fiscal year 2005. These 
limits, however, are significantly different from the pre-2003 HOS 
regulation, which required only 8 hours off duty before driving, 
allowed 10 hours of driving time, and prohibited driving after having 
been on duty for 15 hours (but allowed any off-duty time taken during 
the work shift to be excluded from the calculation of the 15-hour 
limit). The pre-2003 rule had no counterpart to today's 34-hour 
recovery provision. The recovery role was played by the 60- and 70-hour 
limits, the only element of the pre-2003 rule which has been adopted 
without change for property-carrying vehicles in today's rule.
    The 14-hour driving window and the 10-hour off-duty requirement of 
today's rule combine to move most drivers toward a 24-hour cycle, which 
allows the body to operate in accord with its normal circadian rhythm 
and the driver to sleep on the same schedule each day. A driver may 
remain on duty after the 14-hour window closes or go off duty after the 
11th hour of driving, in each case returning to work after 10 hours off 
duty on something other than a 24-hour cycle. Nonetheless, FMCSA 
believes that most drivers, most of the time, will go off duty at or 
before the end of the 14th hour, since their principal responsibility--
driving--is illegal after that point. The circadian friendliness of 
today's rule is bolstered by the requirement for 10 consecutive hours 
off duty. This is enough time to enable drivers to get the 7-8 hours of 
sleep most people need to maintain alertness and prevent the onset of 
cumulative fatigue.
    The original restart provisions were the 60- and 70-hour limits. 
Drivers could not drive after having been on duty for those periods 
until they had been off duty long enough to reduce their 7- or 8-day 
on-duty totals below the 60- or 70-hour threshold. These limits are 
being adopted in today's rule, but the Agency is also adding a second 
and more flexible recovery provision, as it did in 2003--the 34-hour 
restart. A 34-hour period gives a large majority of drivers the 
opportunity for two night sleep periods, and all drivers the 
opportunity for two consecutive 8-hour sleep periods separated by a 
full 18-hour day. Comments to the docket stated that the 34-hour 
restart provides far more flexibility than the 60- and 70-hour limits 
alone, enabling drivers to tailor their schedules to their business 
requirements while still spending more time at home.
    Today's rule also creates a new regulatory regime for drivers of 
CMVs that do not require a CDL, provided they operate within a 150-mile 
radius of their work-reporting location. These drivers are not required 
to keep logbooks, though their employers must keep accurate time 
records, and the driver may use a 16-hour driving window twice a week. 
Driving time may not exceed the normal 11 hours, but the longer 
operational window twice a week enables short-haul carriers to meet 
unusual scheduling demands. Short-haul drivers rarely drive anything 
close to 11 hours, and available statistics show that they are greatly 
under-represented in fatigue-related accidents. On a per-mile basis, 
long-haul trucks are almost 20 times more likely to be involved in a 
fatigue-related crash. One study suggested that a contributing factor 
to this statistical imbalance is the variety of work short-haul drivers 
typically perform; variety seems to minimize fatigue.
    The rule adopted today balances considerations of driver and public 
safety, driver health, and costs and benefits to the motor carrier 
industry--all factors the Agency is required to take into account. The 
provisions are described separately in the preamble, but they 
constitute an interconnected whole and cannot be adequately understood 
in isolation.

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    The rule addresses driver health issues in detail, and provides a 
lengthy explanation and justification for the requirements adopted 
today. FMCSA has examined a wide range of scientific evidence, 
independently collected, summarized, and reviewed by a health panel 
created at the Agency's request by the Transportation Research Board of 
the National Academies of Science. FMCSA has concluded that the 
operation of CMVs under this rule does not have a deleterious effect on 
the physical condition of drivers. Because relatively little of the 
available evidence was derived from motor carrier operations, the 
Agency had to evaluate and weigh information from different fields and 
adapt it to a trucking environment. We believe our conclusions 
accurately reflect a preponderance of the scientific data. The 
additional off-duty time provided by the rule, along with the 14-hour 
driving window, should have a particularly beneficial effect on 
drivers' sleep opportunities, and indirectly on their health as well. 
In an indication of the fatigue-reducing benefits of the 2003 rule, 
preliminary information on sleep habits under that rule shows drivers 
are getting, on average, at least an additional hour of sleep compared 
to the pre-2003 rule. There is no indication that drivers are averaging 
more hours of work, as opponents of the 2003 rule had feared.
    The Agency has examined all of the data on crash risk. Virtually 
every study has weaknesses or limitations. The largest database on 
fatal truck crashes (Trucks Involved in Fatal Crashes, or TIFA) records 
accidents that occurred entirely under the pre-2003 HOS rule, when off-
duty time could have been as short as 8 hours. Furthermore, while the 
crash risk reflected in TIFA data rises with the number of hours driven 
before the crash, the risk in the 11th hour generally reflects illegal 
driving, since the normal limit at the time was 10 hours. Also, despite 
being the largest database available, the data contain relatively few 
fatigue-related crashes after long hours of driving. All in all, we 
thus must be careful in applying this data to the 2003 rule or today's 
rule, where the minimum off-duty time is 25 percent greater.
    On the other hand, we also examined recent data collected while the 
2003 rule was in effect. Although this data suggests that fatigue-
related crashes have fallen since the 2003 rule became effective, this 
newer data is mostly preliminary, self-reported without statistical 
controls, and also reflects small sample sizes, all of which--once 
again--sometimes leads to inconsistent findings.
    The rule and the Regulatory Impact Analysis discuss the strengths 
and weaknesses of each data source and balance the shortcomings of one 
against the advantages of another. The TIFA data from 1991 to 2002 are 
very comprehensive. In order to ensure that its safety analysis erred 
on the side of caution, the Agency used TIFA data to estimate the risk 
of additional driving hours, knowing that the risk is probably over-
stated given the better opportunities for restorative sleep available 
under the 2003 rule and today's final rule. It is also clear that newer 
CMVs, with their quieter and more comfortable cabs, are less fatiguing 
to drive. That change may also affect the usefulness of the TIFA data, 
though this factor is impossible to quantify.
    Using the most conservative estimates of crash risk for a given 
amount of driving time, FMCSA's analysis shows that the safety 
differential between a 10-hour and an 11-hour driving limit is very 
small while the economic cost differential is very large. The 
operational and scheduling flexibility of an 11-hour limit, even when 
it is not utilized fully, is both economically and socially valuable. 
According to the drivers who commented to the docket, the 11-hour limit 
in the 2003 rule enables them to get home more often, when the 10-hour 
limit would leave them stranded at roadside, out of hours. It also 
allows them to get home without pushing quite as hard as they might be 
tempted to do under a 10-hour limit.
    FMCSA examined a range of options and found that today's rule is 
the only one that is cost-beneficial, with a net annual benefit 
estimated at $270 million. Reducing driving time from 11 to 10 hours, 
while leaving the rest of today's rule intact, would increase net costs 
by $526 million per year. To confirm our findings, we conducted a 
sensitivity analysis of the data and assumptions used. We changed these 
parameters in a way that was unfavorable to today's rule in general and 
to allowing 11 hours of driving in particular. No parameters tested, 
either singly or in combination, produced a basis for either replacing 
the 11-hour driving limit with a 10-hour limit, or suggested that 
another option could be more cost-beneficial.

D. Research Review Process

    In preparing this final rule, FMCSA thoroughly, systematically, and 
extensively researched both U.S. and international health and fatigue 
studies and consulted with Federal safety and health experts. In 
addition, FMCSA asked the Transportation Research Board (TRB) of the 
National Academies to contract with a research team of experts in the 
field of health and fatigue to prepare a summary of relevant literature 
through the TRB Commercial Truck and Bus Safety Synthesis Program. The 
literature review was conducted using two teams of health and 
transportation experts to identify and summarize the available research 
literature relevant to this HOS rulemaking. This review included 
research findings that discussed in a scientific, experimental, 
qualitative, and quantitative way the relationship between the hours a 
commercial motor vehicle driver works, drives, and the structure of the 
work schedule (on-duty/off-duty cycles, time-on-task, especially time 
in continuous driving, sleep time, etc.), and the impact on his/her 
health.
    Dr. Peter Orris, M.D., Professor of Occupational Health at the 
University of Illinois, led a team of six prominent medical doctors, 
epidemiologists, and an ergonomist to identify relevant research on CMV 
driver health. Dr. Alison Smiley, President of Human Factors North 
Inc., Professor in the Department of Mechanical and Industrial 
Engineering, University of Toronto, and the Department of Civil 
Engineering, Ryerson University, led a team of three leading 
transportation and fatigue experts to review relevant fatigue studies. 
Each team conducted two literature reviews, a review of the literature 
at the beginning of the project and a review of the literature that was 
submitted by commenters to the 2005 NPRM. It was through this rigorous 
process that FMCSA ensured that not only the latest research, but the 
best available science was used to support this rulemaking. The final 
reports are located in the docket and are entitled ``Literature Review 
on Health and Fatigue Issues Associated with Commercial Motor Vehicle 
Driver Hours of Work,'' Part I and Part II.
    The driver health team used PubMed Central (PMC), which is the U.S. 
National Institutes of Health (NIH) digital archive of biomedical and 
life sciences journal literature. PMC includes MEDLINE, which is the 
premier bibliographic database covering the fields of medicine, 
nursing, dentistry, veterinary medicine, the health care system, and 
the preclinical sciences. MEDLINE contains over 12 million 
bibliographic citations dating back to the mid-1960s and author 
abstracts from more than 4,800 biomedical journals published in the 
United States and 70 other countries.
    The initial driver health literature search from 1975 to present 
resulted in

[[Page 49982]]

over a thousand research articles. The driver health team screened 
these studies based on relevance to the topics of commercial vehicle 
operator health and the health effects of work hours, shift work, and 
sleep schedules. A total of 55 of the relevant studies were reviewed in 
greater detail. Twenty-five were chosen and summarized by a primary 
reviewer to be included in the Part I final report. The criteria for 
inclusion were the validity of the methodology, the relevance of the 
studied population to truck driving, and the quality of the statistical 
analysis of health outcomes.
    Similarly, the TRB driver fatigue team used the TRANSPORT database, 
a bibliographic database of transportation research and economic 
information produced by the 25-nation Organization for Economic Co-
operation and Development, together with the United States TRB, and the 
31 nations of the European Conference of Ministers of Transport (ECMT). 
TRANSPORT includes the Transportation Research Information Services, 
International Road Research Documentation, and ECMT's TRANSDOC.
    Collectively these sources contain over 530,000 citations from 
publications, most with abstracts, of research information on all 
surface transportation modes, air transport, and highway safety. The 
driver fatigue team searched these studies for relevance concerning 
hours of service, and CMV operator performance and fatigue. Because 
FMCSA had previously docketed summaries of fatigue-related studies used 
in preparing the 2003 rule, the scope of this literature review was 
limited to studies published after 1995. Primary sources were selected 
if they addressed truck driver performance (on road or simulated), and 
included driving performance measures (vehicle control or critical 
incidents). Only studies were selected which involved drivers on 
typical work-rest schedules, involving extended hours of driving, 
driving in a sleep-deprived state, and/or driving at night. After the 
initial set of research reports was screened based on relevance, the 
driver fatigue team reviewed a total of 26 relevant studies, and 13 
were chosen to be summarized for the Part I report.
    As a result of the questions posed in the 2005 NPRM, commenters 
referenced over 200 studies. The driver health and fatigue teams 
reviewed the titles and abstracts of studies referenced by commenters 
using the identical criteria that were used for screening the initial 
research discussed earlier. Articles considered most relevant were 
those involving epidemiological studies, studies of CMV crash risk, or 
field studies of performance of commercial drivers in relation to 
fatigue issues such as daily and weekly hours, time of day, and short 
sleep, or studies of non-CMV drivers showing the effects of sleep loss 
and comparing sleep loss and alcohol impacts. The reasons for not 
reviewing the remaining articles suggested by commenters included the 
following: an article was not published as a report of a recognized 
Agency or in a peer-reviewed journal; an article was very general in 
nature (e.g. a discussion of circadian rhythm); or, an article was not 
sufficiently relevant to the task of CMV driving. The driver health 
team selected 11 of these studies to review and summarize for inclusion 
in the Part II report, while the driver fatigue team selected 21 
studies for the Part II report.
    In addition to reviewing the studies mentioned above, FMCSA 
internally reviewed, summarized, and evaluated research reports that 
were previously cited in the 2003 rule, 2004 litigation, 2005 NPRM, and 
driver fatigue and performance studies that were excluded from the TRB 
literature review (i.e., published before 1996).
    The Agency also assembled an intermodal team of experts on operator 
fatigue and health to help FMCSA further identify and analyze relevant 
research. The Federal agencies represented were the Federal Aviation 
Administration, Federal Railroad Administration, U.S. Coast Guard, and 
the National Institute for Occupational Safety and Health (NIOSH).

E. Driver Health

    The D.C. Circuit held that FMCSA failed to consider the possibly 
deleterious effect of the 2003 hours-of-service rule on the physical 
condition of drivers, as required by 49 U.S.C. 31136(a)(4).
    To assess driver health and better comprehend the impact of the 
findings, one must understand the differences in the types of relevant 
medical research. Epidemiology is the study of diseases in populations 
of humans or animals, specifically how, when, and where they occur. 
Epidemiology attempts to determine what factors are associated with 
diseases (risk factors). Epidemiological studies can never prove 
causation; that is, they cannot prove that a specific risk factor 
actually causes the disease being studied. Epidemiological evidence can 
only show that a risk factor is associated (correlated) with a higher 
incidence of disease in the population exposed to that risk factor. The 
higher the correlation the more certain the association, but it cannot 
prove the causation.
    Another type of study is a dose-response study. A dose-response 
study is based on the principle that there is a relationship between a 
toxic reaction (the response) and the amount of substance received (the 
dose). Knowing the dose-response relationship is a necessary part of 
understanding the cause and effect relationship between chemical 
exposure and illness.
    A third type of study is a case-control study, which investigates 
the prior exposure of individuals with a particular health condition 
and those without it to infer why certain subjects, the ``cases,'' 
become ill and others, the ``controls,'' do not. The main advantage of 
the case-control study is that it enables the study of rare health 
outcomes without having to track thousands of people. One primary 
disadvantage of a case-control study is a greater potential for bias. 
Because the health status is known before the exposure is determined, 
the study does not allow for broader-based health assessment.
    These are important distinctions for the following discussion of 
the research on driver health, specifically regarding exposure to 
environmental stressors such as exhaust, chemicals, noise, and 
vibration. FMCSA has reviewed and evaluated the available and pertinent 
information concerning driver health, with emphasis on chronic 
conditions potentially associated with changes from the pre-2003 and 
2003 rules, to this final rule. The research on CMV driver health falls 
into several broad categories: (1) Sleep loss/restriction, (2) exposure 
to exhaust, (3) exposure to noise, (4) exposure to vibration, (5) 
cardiovascular disease, (6) long work hours, and (7) shift work and 
gastrointestinal disorders.

E.1. Sleep Loss/Restriction

    The lack of adequate sleep has been shown to have detrimental 
impacts on the overall health of humans. Research suggests that sleep 
deprivation adversely affects human metabolism as well as the endocrine 
and immune systems [Spiegel, K., et al. (1999), p. 1438]. Chronic 
partial sleep loss is associated with decreased glucose tolerance, 
decreased leptin levels, increases in evening cortisol levels, and 
adverse cardiovascular effects [Spiegel, K., et al. (2004), p. 5770]. 
Consistent with these studies, epidemiologic research demonstrates that 
short sleep duration is modestly associated with symptomatic diabetes 
[Ayas, N. T. et al. (2003), p. 383], cardiovascular disease, and 
mortality [Alvarez, G.G., & Ayas, N. T. (2004), p. 59]. Other studies 
have shown that short sleepers (less than 6

[[Page 49983]]

hours) have hormone and metabolic changes which result in weight gain 
[Hasler, G., et al. (2004), p. 661; Morikawa, Y., et al. (2003), p. 
136; Taheri, S., et al. (2004), p. 210; Vioque, J., et al. (2000), p. 
1683]. Interleukin 6 (IL-6) is a marker of systemic inflammation that 
may lead to insulin resistance, cardiovascular disease, and 
osteoporosis. Sleep loss of as little as two hours per night increases 
daytime IL-6 and causes drowsiness and fatigue during the next day, 
whereas post-deprivation decreases nighttime IL-6 and is associated 
with deeper sleep [Vgontzas, A. N., et al. (2004), p. 2125].
    As to the amount of sleep necessary, the National Sleep Foundation 
recommends 8 hours per day. This standard comes primarily from studies 
by the National Institutes of Health (NIH), which notes that this was 
the mean time period that healthy young adults gravitated to when 
external influences were removed. Not all sleep researchers agree with 
this conclusion, particularly with regard to individual health and 
well-being. Two large-scale studies have found no relationship between 
longer sleep and better health [Kripke, D. F., et al. (2002), p. 131; 
Patel, S. R., et al. (2004), p. 440]. The epidemiological research on 
sleep duration suggests that mortality may even begin to rise with 
sleep durations greater than 8 hours. Likewise, mortality risk 
increases for short sleep durations less than 6 hours per day [Id.].
    The research identified that prior to the 2003 HOS rule, CMV 
drivers were not getting enough sleep (i.e., 7-8 hours per day) as 
needed to maintain individual health. In four major research studies, 
where sleep was verified using either an actigraph watch (wrist-worn 
monitoring device) or electroencephalogram, CMV drivers averaged from 
3.8 to 5.25 hours of sleep per day [Dinges, D. F., et al. (2005), p. 
38; Balkin, T., et al. (2000), p. 4-48; Mitler, M. M., et al. (1997), 
p. 755; Wylie, C. D., et al. (1996), p. ES-10]. These averages are 
below the 6 to 8 hours of sleep that are associated with lower 
mortality or a healthy lifestyle.
    Preliminary data from the following sources suggest that, on 
average, CMV drivers are obtaining more sleep than before under the 
2003 rule, which requires at least 10 consecutive hours of off-duty 
time. First, an ongoing joint National Highway Traffic Safety 
Administration (NHTSA) and FMCSA study conducted in 2005 found that 
drivers were averaging 6.28 hours of sleep per day, a figure that was 
verified with an actigraph watch [Hanowski, R.J., et al. (2005), p.1]. 
Second, in a survey of its membership, the Owner-Operator Independent 
Drivers Association (OOIDA) found that of the 1,264 drivers responding, 
355 or 30 percent of drivers stated that they were getting more rest as 
a result of the 2003 HOS rule with 10 consecutive hours of off-duty 
time. The other 70 percent of the drivers responded that they were 
getting either the same amount of rest or no additional rest was needed 
as a result of the 2003 rule.
    Comparing study findings before and after the 2003 HOS rule change 
suggests that drivers are getting more than an hour of additional sleep 
per night than they previously were able to obtain. While the Agency 
would like to see drivers obtain a sleep period between 7 to 8 hours 
per day to maximize driver alertness, the finding of 6.28 hours of 
sleep per night is within normal ranges consistent with a healthy 
lifestyle and is a vast improvement over previous sleep findings. Based 
on the research that led to the 2003 final HOS rule, FMCSA knew that 
short sleep (less than 6 hours) among drivers was a concern from both a 
safety and health standpoint. As a result, FMCSA increased off-duty 
time to 10 consecutive hours thereby increasing driver sleep by up to 
an additional two hours per day. This final rule adopts the requirement 
for the 10 consecutive hours of off-duty time.

E.2. Exposure to Diesel Exhaust

    The Environmental Protection Agency's (EPA) Health Assessment 
Document for Diesel Engine Exhaust (2002) concluded that ``long-term 
(i.e., chronic) inhalation exposure is likely to pose a lung cancer 
hazard to humans, as well as damage the lung in other ways depending on 
exposure'' [EPA (2002), p. ii].
    Diesel exhaust (DE) is not a single ``thing'' but a mixture of 
hundreds of gases and particles, which differ with the type of engine 
generating them, operating conditions, and fuel formulations. Some of 
the components of DE are known carcinogens (e.g., benzene) and others 
are mutagenic or toxic. Particulates from diesel engines, which 
constitute about 6 percent of the total ambient particulate matter (PM) 
with an aerodynamic diameter of 2.5 micrometers or less (PM-2.5), are 
highly respirable and able to reach the deep lung. Yet EPA has not 
formally declared DE to be a carcinogen. There are several reasons for 
this ambiguity.
    A dose/response curve is the classic means of measuring the effect 
of exposure. A curve is typically established in a laboratory. Very 
high doses are given over a relatively short period, and the 
physiological response is measured. A dose/response curve is assumed to 
be a straight line, which can be extended downward to the lower 
exposures typical of ambient conditions outside the laboratory. If the 
dose/response curve is not a straight line (because the physiological 
response decreases disproportionately when exposure is reduced), the 
curve will overstate the effect of ambient exposure by some unknown 
amount. In that case, long-term population studies might be an 
alternative, provided long-term exposure can be established.
    Attempts to establish a dose/response curve for DE have not 
produced clear-cut results. In animal studies, rats develop lung tumors 
after lifetime inhalation of DE at exposures vastly higher than any 
ambient condition; but these cancers appear to be at least partially 
the result of particle overload, which prevents lung clearance and 
causes chronic inflammation and subsequent lung disease. Chronic 
inhalation studies in mice show equivocal results, and hamsters do not 
develop cancer [Bunn, W.B., et al. (2002), p. S126; EPA (2002), p. 7-
139]. EPA therefore concluded that ``the rat lung tumor response is not 
considered relevant to an evaluation of the potential for a human 
environmental exposure-related hazard'' [Id.]. EPA further noted that 
``[t]he gaseous phase of DE (filtered exhaust without particulate 
fraction) was found not to be carcinogenic in rats, mice, or hamsters'' 
[Id.].
    Although EPA has declared DE to be a ``probable human carcinogen,'' 
based in part on a review of 22 epidemiologic studies of workers 
exposed to DE in various occupations, it also noted that the

    ``Increased lung cancer relative risks generally range from 1.2 
to 1.5, though a few studies show relative risks as high as 2.6. 
Statistically significant increases in pooled relative risk 
estimates (1.33 to 1.47) from two independent meta-analyses further 
support a positive relationship between DE exposure and lung cancer 
in a variety of DE-exposed occupations. The generally small increase 
in lung cancer relative risk (less than 2) observed in the 
epidemiologic studies and meta-analyses tends to weaken the evidence 
of causality. When a relative risk is less than 2, if confounding 
factors (e.g., smoking, asbestos exposure) are having an effect on 
the observed risk increases, they could be enough to account for the 
increased risk'' [EPA (2002), pp. 7-138 and 7-139].

Overall, the evidence is not sufficient for DE to be considered a 
proven human carcinogen because of exposure uncertainties (lack of 
historical exposure data for workers exposed to DE) and an inability to 
reach a full and direct accounting for all possible confounders [Id.].

[[Page 49984]]

    The actual cancer risk involved in operating a diesel-engine truck 
depends on the degree and duration of exposure to DE, and especially to 
smaller particulate matter (PM-2.5). Information on the real-world DE 
exposure of truck drivers is limited by many uncertainties. Because 
trucks spend a great deal of time in motion, the exposure levels of 
different highway, municipal, and regional environments have to be 
collected and combined. Idling time at terminals, in traffic jams, or 
while using a sleeper berth presumably generates higher exposure than 
does highway driving, but estimating the possible combinations of 
conditions for a large population of drivers is difficult. Furthermore, 
because of the long latency period of most cancers, the extent of the 
risk to truck drivers depends on the length of their exposure. This in 
turn is influenced by the factors that existed several decades ago: 
engine design, formulation of diesel fuel, prevalence of smoking among 
driver populations, total particulate levels from all sources, etc. In 
most cases, this information is less well known than comparable data on 
these factors today. Nor can one project previous (assumed) conditions 
forward or current conditions backward; virtually everything about DE 
has been changing in the last few decades and will continue to change 
as EPA tightens the regulations that govern diesel engine design and 
diesel fuel. Also, given EPA initiatives to reduce truck idling, and 
Federal financing available for idle-reduction programs, FMCSA expects 
additional reductions in exposure of CMV drivers to DE.
    Before discussing the studies reviewed by the driver health team, 
it is useful to analyze a potential exposure effect of a feature of the 
2003 rule, which is adopted in this final rule--the availability of 
additional driving and on-duty hours through the use of the 34-hour 
recovery provision. If utilized to the extreme, this would allow 
another 17 hours of driving time and 24 hours of on-duty time in a 7-
day work week, compared to the limit of 60 hours of driving time 
without the recovery provision. To examine the effect of the 2003 rule 
on driver work hours, FMCSA compared an earlier survey of drivers 
operating under the pre-2003 rule with a recently completed survey. In 
a 7-day work week, the 451 drivers who responded to the earlier survey 
worked, on average (driving and other on-duty time), 64.3 hours per 
week [Campbell, K.L., & Belzer, M.H. (2000), p. 104]. In 2005, FMCSA 
evaluated a sample of driver logs and determined that the 489 drivers 
included, with a total of 5,397 7-day periods, worked an average of 
61.4 hours (driving and other on-duty time) per week [FMCSA Field 
Survey Report (2005), p. 4].
    At the annual meeting of the TRB in Washington, D.C. in January 
2005, Schneider National, a large motor carrier, provided a 
distribution of the weekly (8-day period) on-duty hours for its drivers 
(available in the docket for this rule). The data shows that 
Schneider's employee drivers averaged 62 hours on duty per 8-day period 
and its leased drivers averaged 65 hours on duty per 8-day period. In 
addition, J.B. Hunt, another large motor carrier, in comments to the 
NPRM, reviewed the work records of 80 randomly selected over-the-road 
drivers for a 30-day period. J.B. Hunt found that 74 percent of its 
drivers used the 34-hour restart at least once during the 30-day 
period. On average, J.B. Hunt's drivers accumulated 62.25 hours on duty 
per eight-day period.
    This data provides some indication of the hours worked as a result 
of the 2003 rule. Given the data from surveys and comments regarding 
work hours from motor carriers, it does not appear that CMV drivers are 
working on average significantly more hours as a result of the 2003 
rule as compared to the pre-2003 regulation. Consequently, based on 
review of the data, the average exposure of drivers to DE has remained 
essentially unchanged.
    The driver health team identified and reviewed four studies that 
address the issue of hours of work and duration of DE exposure in 
transportation workers. A large case-control study in Germany found 
significant associations between lung cancer and employment as a 
professional driver. The risk reached statistical significance for 
exposures longer than 30 years [Br[uuml]ske-Hohlfeld, I., et al. 
(1999), p. 405]. An exposure response analysis and risk assessment of 
lung cancer and DE found a 1 to 2 percent lifetime increased risk of 
lung cancer above a background risk of 5 percent among workers in the 
trucking industry, based on historical extrapolation of elemental 
carbon levels [Steenland, K., et al. (1998), p. 220]. A large case-
control study of bus and tramway drivers in Copenhagen found a negative 
association between lung cancer and increased years of employment 
[Soll-Johanning, H., et al. (2003), p. 25]. Finally, a meta-analysis of 
29 studies addressing occupational exposure to DE and lung cancer 
showed that 21 of the 23 studies meeting the inclusion criteria, 
observed relative risk estimates greater than one (probability of a CMV 
driver developing lung cancer divided by the probability of the control 
group developing lung cancer). A positive duration response was noted 
in all studies that quantified exposure [Bhatia, R., et al. (1998), p. 
84].
    Several studies have shown an association between truck driving and 
bladder cancer. The driver health team reviewed three studies that 
addressed the association between duration of exposure to DE and 
bladder cancer. A population-based case-control study in New Hampshire 
found a positive association between bladder cancer and tractor-trailer 
driving, as well as a positive trend with duration of employment [Colt, 
J.S., et al. (2004), p. 759]. A large study in Finland found increased 
standard incidence ratios for six types of cancer in truck drivers. 
Cumulative exposure to DE was negatively associated with all cancers 
except ovarian cancer in women with high cumulative exposure [Guo, J., 
et al. 2004, p. 286]. A meta-analysis of 29 studies on bladder cancer 
and truck driving found an overall significant association between 
``high'' exposure to DE and bladder cancer as well as a dose-response 
trend. The authors concluded that DE exposure may result in bladder 
cancer, but the effects of misclassification, publication bias, and 
confounding variables could not be fully taken into account [Boffetta, 
P., & Silverman, D.T. (2001), p. 125].
    As a result of the number of studies showing an association, DE is 
considered to be a ``probable'' carcinogen by the World Health 
Organization and the U.S. Department of Health and Human Services' 
National Toxicology Program. Because of the complexity of proving a 
definitive link between DE and cancer, no organization, other than the 
California EPA, has classified DE as a known carcinogen [Garshick, E., 
et al. (2003), p. 17]. Studies have a great degree of uncertainty due 
to study design and exposure assumptions, measurement issues, and 
synergistic effects of various pollutants, among other variables. 
[Bailey, C.R., et al. (2003), p. 478]. Excluding rats, animal studies 
are overall negative with regard to lung tumor formation following DE 
exposure. In rats, lung tumors are produced by lifetime inhalation 
exposure to many different particle types. These exposures are 
characterized as ``lung overload;'' however, numerous analyses point to 
a lack of relevance of data from lung-overloaded rats to human risk 
calculations, particularly at environmental or ambient levels [Bunn, 
W.B., et al. (2002), p. S122]. As noted earlier, EPA's risk assessment 
on DE, based on long-term (chronic) exposure,

[[Page 49985]]

concludes that DE is ``likely to be carcinogenic to humans by 
inhalation.'' Studies show a causal relationship between exposure to DE 
and lung cancer, but EPA has not concluded that DE is a human 
carcinogen and cannot develop a quantitative dose-response cancer risk. 
The rat inhalation studies underpinning these findings resulted from 
overloading DE and are unrealistic exposure scenarios for humans [Ris, 
C. (2003), p. 35].
    The acute (short-term) effects of DE, which would allow us to 
determine safe exposure levels, are not currently known [Id.]. Also, 
there are not enough human test data to make a definitive risk 
assessment on the chronic long-term respiratory effects of DE. Tests on 
animals, however, suggest chronic respiratory problems exist [Id.]. 
Cleaner burning diesel fuel standards (2006) combined with cleaner 
diesel engine technologies from more stringent emission standards 
(2007) will generate a net reduction in pollutant emissions, despite 
growth in diesel use [Sawyer, R.F. (2003), p. 39].
    EPA models project on a national basis the amount of emissions or 
pollutants expected annually from all mobile sources. These are based 
on estimates of vehicle miles traveled and new vehicles entering and 
old vehicles leaving the inventory, and they reflect changes in vehicle 
emissions standards. The models project emissions for the following 
pollutants: Carbon Monoxide, Oxides of Nitrogen, Volatile Organic 
Compounds, Particulate Matter (PM-2.5), Particulate Matter (PM-10), and 
Sulfur Dioxide. EPA estimates show that vehicle emissions from all 
mobile sources have declined significantly from 1990 to 2005 (average 
35 percent reduction in emissions) and are projected to decline further 
until 2030 (average 55 percent reduction in emissions). DE from heavy 
vehicles represents about 23 percent of all emissions from mobile 
sources. DE from heavy vehicles has also declined from 1990 to 2005 
(average 55 percent reduction in emissions) and is projected to decline 
further until 2030 (average 88 percent reduction in emissions). The 
following chart shows the projections of heavy vehicle DE from the on-
the-road fleet by type of emission from 1990 to 2030. The chart is 
based on U.S. EPA's ``National Annual Air Emissions Inventory for 
Mobile Sources,'' which was conducted for a variety of pollutants 
emitted by on-road vehicles. [EPA (January 2005)]. Mobile source 
emission inventories were directly modeled for 2001, 2007, 2010, 2015, 
2020, and 2030. Other years were obtained by linear interpolation. 
EPA's Air Inventory was developed using the National Mobile Inventory 
Model [EPA (March 2005)].
[GRAPHIC] [TIFF OMITTED] TR25AU05.000

    If diesel or all engine emissions are in fact carcinogenic (not yet 
proven), then the risk of developing cancer is a function of both the 
amount of DE being inhaled and cumulative exposure (time). Based on EPA 
emission projections of lower emissions from on-the-road heavy 
vehicles, continued reduction in health impacts can be expected over 
time.
    It appears that chronic (long-term) exposure to DE may cause 
cancer. The exposure/dose required, however, is currently unknown due 
to the extreme difficulty in measuring and modeling exposure. EPA has 
noted that there is great

``uncertainty regarding whether the health hazards identified from 
previous studies using emissions from older engines can be applied 
to present-day environmental emissions and related exposures, as 
some physical and chemical characteristics of the emissions from 
certain sources have changed over time. Available data are not 
sufficient to provide definitive answers to this question because 
changes in DE composition over time cannot be confidently 
quantified, and the relationship between the DE components and the 
mode(s) of action for DE toxicity is unclear'' [Ris, C. (2003), p. 
35].

    Some of those flaws might be addressed by Garshick's effort to 
quantify lung cancer risk in the trucking industry through an 
epidemiological study using up to 72,000 subjects [Garshick, E., et al. 
(2002), p. 115]. At this time, however, according to EPA,

[[Page 49986]]

NIOSH, the Centers for Disease Control and Prevention, and NIH, there 
is not enough evidence to declare DE a carcinogen. Nonetheless, EPA's 
finding that DE is a probable carcinogen is a cause for concern. EPA 
has therefore adopted new diesel engine performance requirements and 
will by 2007 require refiners to produce low-sulphur fuel [66 FR 5002]. 
EPA's previous and forthcoming regulatory changes lead to a projection 
of dramatically lower DE through 2030, which will greatly reduce any 
health effects of DE exposure.
    Still, the question remains whether today's rule, regarding 
exposure to DE, ensures that ``the operation of commercial motor 
vehicles does not have a deleterious effect on the physical condition'' 
of CMV drivers [49 U.S.C. 31136(a)(4)]. After reviewing all the studies 
mentioned, there is no evidence that today's rule has a deleterious 
effect. This is not to deny the possibility that DE may have some 
impact on truck drivers. The Agency, however, cannot attempt to address 
a problem without data on its extent and severity. The data on exposure 
to DE is notoriously deficient. As Garshick and his colleagues noted,

    ``The ideal marker of DE exposure would be a single marker that 
would be inexpensive, easy to measure, and clearly linked to the 
source of diesel emissions. However, the reality is that DE is a 
complex mixture, and in many real-life scenarios it may not be the 
only important source of exposure to the individual particles and 
gases that constitute DE. In addition, the mechanism of the health 
effects and specific causal agents are uncertain. The best diesel 
exposure marker is likely to be more complex and involve the 
measurements of molecular organic tracers and elemental carbon. The 
nature of the exposure assessment and marker chosen may also depend 
on mechanism of health effect postulated, and may include 
measurement of exhaust gases (such as ozone and nitrogen oxide) in 
the setting of nonmalignant respiratory diseases. Although current 
literature identifies DE as a health hazard, insight into a dose-
response relationship is limited by factors related to both cohort 
selection and exposure assessment. The development of an exposure 
model in the existing DE epidemiologic literature is hindered by a 
lack of exposure measurements upon which an exposure model can be 
developed, uncertainty regarding the best measurement or marker(s) 
indicative of exposure, and uncertainty regarding historical 
exposures'' [Garschick, E., et al. (2003), p. 21].

    One of the best works to date on DE, lung cancer, and truck driving 
is a series of studies by Steenland and his colleagues published 
between 1990 and 1998. The abstract of the 1998 study concludes that, 
``[r]egardless of assumptions about past exposure, all analyses 
resulted in significant positive trends in lung cancer risk with 
increasing cumulative exposure. A male truck driver exposed to 5 
micrograms/m3 of elemental carbon (a typical exposure in 
1990, approximately five times urban background levels) would have a 
lifetime excess risk of lung cancer of 1-2 percent above a background 
risk of 5 percent.'' The difference between 1 percent and 2 percent is 
obviously quite large, but the absence of a dose/response curve for DE 
and uncertainties in the exposure data make greater precision 
impossible.
    In 1999, however, the Health Effects Institute (HEI), a non-profit 
corporation chartered in 1980 to assess the health effects of 
pollutants generated by motor vehicles and other sources, and supported 
jointly by EPA and industry, found significant flaws even in the 1998 
Steenland study. As summarized by Bunn et al. [Bunn, W.B., et al. 
(2002), p. S127], the HEI found that the Steenland study ``quite likely 
suffers from an inadequate latency period, making it completely 
unsuitable for reaching any qualitative or quantitative conclusions 
about the link between DE exposure and lung cancer.'' Furthermore, the 
workers in the study were exposed to an inseparable mix of gasoline and 
diesel fumes. ``Indeed, during the 1960s (the critical years of the 
Steenland study from a latency perspective), diesel fuel represented 
only 4-7 percent of the total fuel sales (cars and trucks). Moreover, 
in the 1960s, gasoline-fueled vehicles had no after-treatment, so that 
emissions from gasoline-fueled vehicles likely would have been 
comparable to those from diesel vehicles'' [Id.].
    Given the uncertain effects of exposure to DE, FMCSA could not 
include this factor in any cost/benefit analysis for any regulatory 
change it wished to consider. Some changes are beyond FMCSA's 
authority. EPA has exclusive authority to set emission standards for 
new trucks, and NHTSA has comparable jurisdiction over equipment 
standards for new vehicles. FMCSA retains a degree of authority to 
order the retrofitting of safety equipment to vehicles already in 
service [see 49 CFR 1.73(g)], but it is unclear what CMV equipment, if 
any, could be installed on the current fleet to reduce the driver's 
exposure to DE. A driver's ability to open one or both side windows 
could defeat any air-cleaning technology that might be added to the 
tractor, and all drivers spend time outside the vehicle at terminals, 
truck stops, and other locations where exposure to DE is unavoidable.
    Another possible means of reducing drivers' DE exposure would be to 
curtail driving and on-duty time, or even to limit a driver's career to 
a certain number of years, all in the interest of improved health. As 
indicated above, however, there is no dose/response curve for DE and 
the Agency could not be sure that a given reduction in hours or years 
of service would produce a clear benefit. Forced retirement after a 
certain number of years on the job is especially problematical. There 
is nothing in the legislative history of 49 U.S.C. 31136(a)(4) to 
indicate that Congress wanted FMCSA to protect the health of drivers by 
limiting their livelihood. A limit on driving or on-duty hours for the 
specific purpose of reducing DE exposure seems unnecessary, because the 
available evidence shows that drivers have not increased their driving 
or on-duty time in response to the 2003 rule.
    One of the benefits of the 2003 HOS rule has been that it limits 
driver duty periods to 14 consecutive hours per day with no extensions 
for intervening off-duty periods. Under the pre-2003 rule, drivers were 
allowed a 15-cumulative-hour duty period but could extend their maximum 
duty period indefinitely by taking off-duty time during their workday. 
This perpetuated the problem of excessive waiting time for pick up and 
delivery of freight at shippers and receivers, because the drivers were 
expected to place themselves in off-duty status while waiting. A 1999 
study of dry freight truckload carriers by the Truckload Carriers 
Association (TCA) revealed that drivers spent nearly seven hours 
waiting for each freight shipment that they picked up and delivered.
    The non-extendable 14-hour provision of the 2003 rule has given 
motor carriers greater leverage to insist that shippers and receivers 
reduce waiting time. At the 2005 Annual Meeting of the Transportation 
Research Board (TRB) in January 2005, in Washington, DC, several large 
carriers stated that as a result of the 14-hour rule, they are 
increasingly charging detention fees when shippers and receivers cause 
delays. As a result of the 14-hour provision, shippers and receivers 
have had to improve the efficiency and productivity of loading docks. 
Many drivers have commented that waiting time has been signifi