Federal Register: RULES Motor carrier safety standards: [49 CFR Parts 385 and 395]

DEPARTMENT OF TRANSPORTATION

Federal Motor Carrier Safety Administration

CFR Citation: 49 CFR Parts 385 and 395

Docket ID: [Docket No. FMCSA-2004-19608]

NOTICE: RULES

ACTION: Motor carrier safety standards:

DOCUMENT ACTION: Interim final rule (IFR); request for comments.

SUBJECT CATEGORY: RIN-2126-AB14

DATES: This rule is effective December 27, 2007. Comments must be received on or before February 15, 2008.

DOCUMENT SUMMARY: FMCSA amends the Federal Motor Carrier Safety Regulations effective December 27 to allow commercial motor vehicle (CMV) drivers up to 11 hours of driving time within a 14hour, nonextendable window from the start of the workday, following 10 consecutive hours off duty (11hour limit). This interim rule also allows motor carriers and drivers to restart calculations of the weekly onduty time limits after the driver has at least 34 consecutive hours off duty (34hour restart). An IFR is necessary to prevent disruption to enforcement and compliance with the hoursofservice (HOS) rules when the stay expires, as well as possible effects on the timely delivery of essential goods and services. This IFR will ensure that a familiar and uniform set of national rules governs motor carrier transportation, while FMCSA gathers public comments on all aspects of this interim final rule, conducts peer review of our analysis, and considers the appropriate final rule that addresses the issues identified by the Court. FMCSA is fully committed to issuing a final rule in 2008.

SUMMARY: Drivers’ hours of service—; On-duty driving time adjustments,

DOCUMENT BODY 2:
Hours of Service of Drivers

SUPPLEMENTAL INFORMATION

Table of Contents
A. Legal Basis for the Rulemaking
B. Why This Interim Final Rule Is Necessary
C. Background
D. FMCSA's Response to the Court's Decision
E. Evaluation of Issues Concerning the Regulatory Impact Analysis F. Evaluation of Recent Safety and Operational Data Under the 11 Hour and 34Hour Rules
G. Regulatory Analyses and Notices

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 hoursofservice (HOS) regulations adopted in this interim rule pertain directly to 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, the Federal Motor Carrier Safety Administration (FMCSA) must also consider their ``costs and benefits'' [49 U.S.C. 31136(c)(2)(A) and 31502(d)]. Those factors are also discussed in this interim rule.

B. Why This Interim Final Rule Is Necessary

After the United States Court of Appeals for the District of Columbia Circuit (the Court or D.C. Circuit) decision in OwnerOperator Independent Drivers Association, Inc. v. Federal Motor Carrier Safety Administration, 494 F.3d 188 (D.C. Cir. 2007), FMCSA carefully analyzed the current situation to determine the appropriate action to take in response to the decision. It is important to note that the D.C. Circuit found fault with various procedures related to the Agency's adoption of the 11hour limit and the 34hour restart, but not with their substance. This analysis included a review of the safety data concerning motor carrier operations, particularly with respect to fatiguerelated fatal crashes. The discussion below further explains the analysis and reasoning that has led FMCSA to determine this IFR is necessary to ensure that a familiar and uniform set of national rules governs motor carrier transportation, while FMCSA gathers public comments and information and considers the appropriate final rule, which FMSCA is fully committed to issuing in 2008.

We found that the 2005 rule has maintained highway safety outcomes while enhancing operational flexibility for the motor carrier industry. Every alternative, including immediate restoration of a 10hour driving limit with no 34hour restart, entails a risk of disrupting that achievement. As mentioned above, in the years since 2003, when the 11 hour driving limit and 34hour restart provision were adopted (along with the critically important 10hour minimum daily offduty period), there has been no upward trend in the number of fatal crashes as a whole or fatiguerelated fatal crashes in particular. In fact, the 2006 fatality rate per 100 million vehicle miles traveled (VMT) by combination unit trucks (mostly standard tractortrailer
[[Page 71249]]
combinations) is the lowest since the Department of Transportation began keeping such statistics over 30 years ago. The percentage of large truck fatal crashes where the driver was coded as fatigued has remained essentially the same since 2003, despite small fluctuations. Similarly, the percentage of largetruck fatalities in the 11\th\ hour of driving where the driver was coded as fatigued has remained below the average of the years 19912002 since 2003. The D.C. Circuit found fault with various procedures related to the Agency's adoption of the 11hour limit and the 34hour restart, but not with their substance. These provisions are part of an effective safety rule and must be preserved while the Department addresses the issues identified by the Court.

We then examined the alternatives available to the Agency in light of the Court's decision and our statutory responsibilities. We believe, based on reading the Court's decision in conjunction with the current text of the regulation, that there is strong likelihood of confusion regarding what HOS rules will be in effect on December 27, 2007, when the Court's mandate issues. For example, drivers and motor carriers could read the Court's decision to vacate certain provisions of the 2005 HOS rule in light of 49 CFR 395.0 and conclude that there is no daily driving limit in effect. Alternatively, issuance of the Court's mandate could be viewed as an immediate restoration of the former 10 hour driving limit with no 34hour restart. Regardless of how the Court's action is interpreted, we are certain that issuance of the mandate will lead to sufficient confusion and uncertainty concerning what HOS rules govern, and result in poor compliance by the motor carrier industry, as well as reduced and inconsistent enforcement by Federal and State officials. FMCSA provides grants to States that agree to adopt and enforce State laws or regulations compatible with the Federal safety regulations. Some adopt Federal rules by reference, while others require the legislature to enact a special measure adopting the Federal rule; many allow an administrative agency to adopt a rule, but only after publishing a notice and giving the public a chance to comment. Because of wide variations in adoption procedures and schedules, States have three years to adopt such regulations. In order to respond adequately to the Court's procedural concerns we believe that, to respond to the Court's decision, we need to issue an IFR, with an opportunity for public comment, to ensure there will not be a patchwork of laws across the nationwith some States enforcing a 10hour limit while others enforce no limit, and still others retained the 2005 limitswithout a clear general understanding of what Federal regulation is in place . Undoubtedly, this would create confusion, inconsistency, and have an unpredictable impact on safety, since law enforcement may reduce its enforcement as a result of varying State laws. To remain legal, each driver would need to know the HOS limits in each State where he or she operated; this is simply impractical. Drivers could not be sure how their actions in one State would be treated in a State with a different HOS regime; officers might reduce their enforcement efforts to avoid the perception of unfairness. Uncertainty is the enemy of enforcement and compliance; it can only impair highway safety. This IFR will ensure that a familiar, uniform set of national rules govern motor carrier transportation, while FMCSA gathers additional public comments on all aspects of this interim final rule, conducts peer review of our analysis, and considers an appropriate final rule that addresses the issues identified by the Court. FMCSA is fully committed to issuing a final rule in 2008.

Additionally, an immediate restoration of a 10hour driving limit with no restart provision or entirely eliminating the daily driving limit would cause disruption and transition costs. The affidavits of motor carrier officials filed by American Trucking Associations, Inc. (ATA) in support of its stay motion in the D.C. Circuit (and described in more detail below) bear witness to the recruitment, training, operational, and equipment costs motor carriers would face, amounting in the aggregate to scores and perhaps hundreds of millions of dollars. The costs are not merely transitional, however. Our failure to issue an IFR could inflict a loss of scheduling flexibility on the industry and ultimately raise the cost of highway transportation. There could also be adverse safety implications, as new and inexperienced drivers are hired to handle loads that could not consistently be delivered in the absence of the provisions vacated by the Court. New drivers are less safe than veteran operators and would inevitably become involved in crashes that a more experienced driver population would avoid. The costs of added crashes are very substantial. The IFR avoids all of these problems.

The IFR will also allow FMCSA and commenters to the docket additional time to evaluate more recent data and determine the appropriate final hours of service rule while avoiding shifting the requirements back and forth. Although our analysis indicates these policies are the right ones to adopt on an interim basis, FMCSA specifically requests comment on all the conclusions reached in this preamble and Regulatory Impact Analysis (RIA). FMCSA is also submitting its analysis to peer review. FMCSA is committed to issuing in 2008 a final rule fully responding to all comments to this IFR.

For example, with respect to the 11hour driving limit and the 34 hour restart, the more recent data continue to support them. Although the D.C. Circuit raised concerns with the Agency's treatment of the Trucks Involved in Fatal Accidents (TIFA) data for crashes that occurred beyond the 11th hour in the 2005 rule, the Agency has employed a more sophisticated analysis discussed below that shows a lower risk from driving in the 11th hour than under FMCSA's earlier method. The modeling of time on task (TOT) developed for the 2005 rule was complex and comprehensive and remains the best available study of its kind. The D.C. Circuit faulted the Agency for failing to make this model available for notice and comment; this IFR corrects that oversight, and the RIA provides a more detailed explanation of the Agency's methods. Analysis of further data collected for the Virginia Tech Transportation Institute (VTTI) operational study supports the preliminary results described in the 2005 rule: There is no increase in ``critical incidents'' (a surrogate for crash risk) in the 11th hour of driving. FMCSA's very recent survey data show that, while the 11th hour and the 34hour restart provisions are being used more often than in 2005, virtually no one attempts to use every minute of driving or onduty time theoretically allowed by the regulations, just as the Agency predicted in the 2005 rule. Furthermore, the analysis of fatigue related crashes by day of the week, described in detail later in the preamble, also supports the belief that the 34hour restart is not resulting in increases in fatiguerelated fatal crashes. FMCSA is not required to demonstrate that constant, maximum utilization of the HOS rules is as safe as the pre2003 rules, when operational constraints (heavy traffic, shortages of parking and truck driver sleeping facilities, waiting time at terminals, eating and refueling, etc.) make it impossible to achieve that degree of utilization except for brief periods. The 2005 rule analyzed the safety implications of the HOS rules in
[[Page 71250]]
the real world, and all of the safety data for subsequent years have borne out the Agency's conclusion that the rule skillfully and successfully combines safety with operational benefits. These are the outcomes this IFR seeks to maintain.

C. Background

The HOS rules limit the number of hours a driver may operate a commercial motor vehicle (CMV) during each workday, the length of the workday within which driving may occur, the minimum offduty period before starting the next workday, and the cumulative number of onduty hours during the work week after which a CMV may not be driven. The rules also allow for the use of a sleeper berth to accumulate the equivalent of 10 consecutive hours off duty. Prior to April 2003, FMCSA and its predecessor agencies limited driving time to 10 hours within a 15hour, extendable workday or window. In practice, the 15hour window could be substantially longer than 15 hours because miscellaneous off duty periods were not counted as part of the 15 hours. Drivers were required to have at least 8 consecutive hours off duty prior to the beginning of a new 15hour duty window. Drivers using a sleeper berth could split their time in the sleeper berth into two separate periods to accumulate the equivalent of 8 consecutive hours off duty provided neither period was less than 2 hours. Drivers working for a carrier that operated 6 days each week could not drive CMVs after 60 hours on duty in a 7 consecutiveday period; drivers working for a carrier that operated CMVs 7 days each week and which chose to operate under an alternate work schedule to the 60hour rule, could not drive CMVs after 70 hours on duty in an 8 consecutiveday period. In practice, drivers on certain schedules could ``run out'' of available onduty time within a few days and be forced to go off duty for approximately 3 full days before being allowed to drive again, regardless of whether the driver may have fully recovered from the work demands in a shorter period of time.

In April 2003, FMCSA published a final rule that changed the requirements for drivers of propertycarrying CMVs. (68 FR 22456, April 28, 2003) (``2003 Rule'') Driving was limited to 11 hours within a 14 hour, nonextendable window after coming on duty, following 10 consecutive hours off duty (known as the 11hour limit). Although the 60 and 70hour rules were unchanged, drivers could restart the calculation during any weekly time period after they took 34 consecutive hours off duty (known as the 34hour restart provision). Drivers using sleeper berths were allowed to continue to split the mandatory off duty period, with the minimum period in the sleeper berth being 2 hours. (Drivers of passengercarrying CMVs are still required to operate under the pre2003 rules.)

The 2003 rule contained several provisions that, when taken together, improved the opportunity for drivers to obtain restorative sleep, thus decreasing the likelihood of driver fatigue. For example, among the most significant provisions, the rule established a 14hour, nonextendable window within which a driver could drive up to 11 hours, following a 10 consecutive hour offduty period. This provision moved drivers toward a workrest schedule that more closely matched the natural circadian cycle of 24 hours and gave drivers the opportunity to obtain the 7 to 8 hours of uninterrupted sleep per day that most adults need. The 34hour restart provision also gave drivers the opportunity for two 8hour sleep periods, which research has shown can overcome cumulative fatigue associated with sleep deprivation. Because the duty period within which an operator could drive was more limited than under the pre2003 rule and because the rest period was long enough to provide an opportunity for 7 to 8 hours of uninterrupted sleep time, FMCSA concluded it was safe and reasonable to extend the number of hours an operator could drive within the 14hour window from 10 hours to 11 hours. The 34hour restart provision also gave drivers and carriers operational flexibility and an improved quality of life, particularly for long haul operations, where the 7 and 8day limits may limit flexibility by forcing drivers to go off duty for periods longer than necessary to fully recover from a typical work week. FMCSA concluded that the 14hour rule and the mandatory 10hour offduty period improved safety while providing operational flexibility that the 11 hours of driving time and the 34hour restart provide.

In April 2004, the Court overturned the 2003 rule on the grounds that FMCSA did not address the issue of driver health, as required by 49 U.S.C. 31136(a)(4). (Public Citizen v. FMCSA, 374 F.3d 1209, D.C. Cir. 2004) The Court also indicated that it had concerns about the rationale for other provisions in the rule. However, to avoid industry disruption and burden on the States, Congress enacted section 7(f) of the Surface Transportation Extension Act of 2004. This section provided that the 2003 rule would remain in effect until a new final rule addressed the Court's issues or until September 30, 2005, whichever occurred first.

After reviewing the decision and considering the concerns raised by the Court, FMCSA decided to repropose the rule as originally published in 2003 and to seek public comments. (70 FR 3339, Jan. 24, 2005) On August 25, 2005, FMCSA published a final HOS rule that retained most of the provisions of the 2003 rule. (70 FR 49978, Aug. 25, 2005) (``2005 Rule'') The Agency significantly strengthened the 2003 rule by requiring drivers using sleeper berths to spend at least 8 but less than 10 consecutive hours in the sleeper berth and take an additional 2 hours either off duty or in the sleeper berth. The new requirement provided drivers the opportunity to obtain 7 to 8 hours of uninterrupted sleep each day. Also, the Agency required that the shorter sleeper berth period be counted against the 14hour onduty limit decreasing the extent to which the workday could be extended. The 2005 rule also provided relief to some shorthaul operations using lighter trucks.

The purpose of the HOS rules is to reduce the likelihood of driver fatigue and of fatiguerelated crashes. Although the rules that existed before 2004 (the effective year of the 2003 rule) allowed less daily driving time than the 2003 and 2005 rules (10 hours versus 11 hours), the driving could occur 15 hours or more after the driver started working without any opportunity for intervening restorative rest or sleep, and followed a shorter minimum rest period (8 hours versus 10 hours). The change to a 14hour nonextendable window and a 10hour rather than an 8hour rest period was intended to limit the period in which a driver could operate a CMV and provide the driver with a work schedule that was consistent with the normal 24hour biological clock. The 2005 rule did not limit the number of hours a driver can perform work other than driving, but if a driver worked after the 14th hour, he or she must take at least 10 consecutive hours off duty after finishing work before again operating a CMV. The change to a 10hour offduty requirement also recognized that drivers may do other things in their offduty time besides sleeping; the 10hour break gives them an opportunity to obtain the 7 to 8 hours of sleep most people need to be rested and to carry out other daytoday personal activities. The 34 hour restart provision provides drivers with an opportunity to obtain two 8hour rest periods, which research indicates can overcome cumulative sleep deprivation. Similarly, the 2005 change to the sleeper berth provisions eliminated the
[[Page 71251]]
practice of splitting time in the sleeper berth into increments that were too short to provide an opportunity for 7 to 8 consecutive hours of sleep.

FMCSA addressed the issue of driver health in the 2005 rule, as required by 49 U.S.C. 31136(a)(4). In preparing the 2005 rule, FMCSA 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 the 2005 rule. This review included research findings that discussed the relationship between the hours a commercial motor vehicle driver works, drives, and the structure of the work schedule (onduty/ offduty cycles, timeontask, especially time in continuous driving, sleep time, etc.), and the impact on his/her health. The research studies cited in this interim rule are included in the List of References in the 2005 final rule (70 FR 49978, at 50067). Copies or abstracts are in the docket referenced at the beginning of this notice.

FMCSA reaffirms its findings on driver health outlined in the 2005 final rule. For a complete discussion of the health of drivers operating under the HOS rules, see the August 25, 2005 final rule (70 FR 49978, at 49982).

Public Citizen and others challenged the August 2005 rule on several grounds, as did the OwnerOperator Independent Drivers Association (OOIDA). On July 24, 2007, the Court rejected OOIDA's arguments, which focused on the sleeper berth provision, but accepted part of Public Citizen's arguments and vacated the 11hour driving time and 34hour restart provisions (OwnerOperator Independent Drivers Association, Inc. v. Federal Motor Carrier Safety Administration, 494 F.3d 188 (D.C. Cir. 2007)). Public Citizen challenged the provisions on four grounds. First, Public Citizen contended that FMCSA's actions were inconsistent with the Administrative Procedure Act (APA) requirement for notice and comment rulemaking because the Agency did not disclose in time for comment the methodology of a model central to the Agency's justification for the rule. Second, when the methodology was disclosed, FMCSA did not provide an explanation for some of its critical elements, thus rendering the rule arbitrary and capricious. Third, FMCSA's treatment of a number of other safety considerations was also arbitrary and capricious. Finally, Public Citizen argued that the rule failed to protect driver health. The Court vacated the rule provisions based on the first two arguments and did not address the last two.

The Court concluded that FMCSA did not satisfy the APA's requirements because the Agency failed to provide an opportunity for public comment on the methodology of the Agency's operatorfatigue model, which FMCSA used to assess the costs and benefits of alternative changes to the HOS rules. In particular, the Court found the Agency had not adequately disclosed and made available for review the modifications it made to the 2003 operatorfatigue model to account for timeontask effects in the 2005 analysis. The Court concluded that the methodology the Agency used changed and did not remain constant from 2003 to 2005 because the timeontask element in the model was new and constituted the Agency's response to a defect in its previous methodology. The Court listed several elements of the process by which the Agency calculated the impact of timeontask that it held could not have been anticipated and that were not disclosed in time to allow for public comment.

The Court also found, turning to Public Citizen's second argument, that FMCSA did not provide an adequate explanation for certain critical elements in the model's methodology. As its basis for vacating the increase in the daily driving limit from 10 to 11 hours, the Court found arbitrary and capricious what it described as FMCSA's ``complete lack of explanation for an important step in the Agency's analysis,'' i.e., the manner in which it had plotted crash risk as a function of timeontask/hours of driving. The Court also found that FMCSA failed to provide an explanation for its method for calculating risk relative to average driving hours in determining its estimate of the increased risk of driving in the 11th hour. As its basis for vacating the 34hour restart provision, the Court found that FMCSA also provided no explanation for the failure of its operatorfatigue model to account for cumulative fatigue due to the increased weekly driving and working hours permitted by the 34hour restart provision.

Based on these two findings, the Court found it unnecessary to reach Public Citizen's other two arguments. In addition, the Court rejected three additional challenges to the 2005 Rule raised by OOIDA.

In an order filed on September 28, 2007, the Court granted a 90day stay of the mandate. The Court directed that issuance of the mandate be withheld until December 27, 2007.

D. FMCSA's Response to the Court's Decision

This rulemaking addresses the issues that were identified by the Court in overturning two provisions of the 2005 rule. It seeks comment on the methodology of the model central to the justification for this IFR. It is based on the Agency's evaluation of new safety and operational data, additional analysis and modeling of the relationship between hours of driving and fatiguerelated large truck crashes, discussion of the concept of cumulative fatigue in the context of driving activity, and the collection and evaluation of new data on the benefits and costs of the 11hour driving limit and the 34hour restart provisions. As an additional step to ensure the soundness of the Agency's analytical methods, we are subjecting our analysis to peer review.

By readopting the 11hour limit and the 34hour restart, the Agency's intent is to allow motor carriers and drivers to combine work rest schedules that follow the optimal 24hour circadian cycle (10 hours off duty and 14 hours on duty) while maintaining highway safety with operational flexibility. By adopting these rules as interim, the Agency is seeking to avoid significant and costly disruption of existing industry compliance and State enforcement practices while ensuring that the actions and underlying safety analysis are available for comment from all interested parties before issuing a final rule. In the meantime, this will ensure that an uninterrupted safety regime remains in place with State enforcement laws, policies, and personnel.

The 2005 rule includes a provision stating that ``[a]ny regulations on hours of service of drivers in effect before April 28, 2003, which were amended or replaced by the final rule adopted on April 28, 2003 [69 FR 22456] are rescinded and not in effect'' (Sec. 395.0). Because the D.C. Circuit did not address this provision, either in OOIDA v. FMCSA or in its response to FMCSA's response in support of ATA's motion for a stay, the Agency must now adopt an IFR to forestall the significant confusion that would otherwise occur in the motor carrier industry, interfering with efforts to restore an orderly HOS regime.

The two provisions being adopted in this rule, on an interim basis, are part of a broader, critical set of five HOS
[[Page 71252]]
provisions included in this IFR. The other three critical provisions of the 2005 rule are: (1) The increase in the minimum offduty period from 8 consecutive hours to 10 consecutive hours to ensure drivers have an opportunity to obtain up to 8 hours of sleep; (2) the establishment of a 14hour, nonextendable window from the start of the workday within which all driving must be completed; and (3) the modification of the sleeperberth rule to require an 8hour sleeper berth period, thereby ensuring that drivers have an opportunity to obtain up to 8 hours of uninterrupted sleep. These provisions function along with the 11hour limit and the 34hour restart provision to protect against degradation of driver's cognitive or psychomotor skills due to fatigue.

Section E describes additional analysis conducted since 2005 that validates the modeling relied upon by the Agency to examine the relationship between the risk of a fatiguerelated large truck crash during the 11th hour of driving. It also addresses cumulative fatigue as it relates to the driving and restart provisions. In its analysis of the 34hour restart provisions being adopted in this IFR, the Agency reexamined the research pertaining to long work hours and sought additional research completed after the 2005 rule. The Agency found no new research that addressed the relationship of long work hours to motorvehicle driving safety.

Safety data collected and analyzed since the 2003 HOS rule became effective, described below in Section F, address the impact of the 11 hour driving limit and the 34hour restart provisions and validate the Agency's argument that safety has been maintained under these provisions. The Agency has collected new operational data, described in Section F, that support its prior conclusions with regard to the cost benefit analysis of the 11hour driving limit and the 34hour restart provision. These data also suggest that reverting to the pre2003 rule 10hour driving limit and eliminating the 34hour restart provisions would be significantly disruptive to drivers, carriers, and to the States where most of the enforcement of HOS violations occur. It would also be disruptive to the safe and efficient movement of freight and cause delays in the delivery of essential goods and services to the American people.
E. Evaluation of Issues Concerning the Regulatory Impact Analysis

The D.C. Circuit's 2007 decision held that FMCSA failed to provide an adequate opportunity for review of certain aspects of the RIA. The Agency is providing a 60day opportunity for review and comment on the RIA supporting this interim rule and the interim rule itself. Since the public has submitted comment on many aspects of this analysis in previous rulemakings, and given the Agency's desire to issue a final rule in a timely fashion, FMCSA believes 60 days is an adequate amount of time to afford the public opportunity for comment.

The Court also held that the Agency had not provided an adequate explanation for two critical elements of the model in the RIA accompanying the 2005 rule: (1) The analysis of timeontask; and (2) the analysis of how the 34hour restart affected cumulative fatigue. This section addresses these two topics. First, in support of this interim rule the Agency has reevaluated how the effects of extended driving hours (i.e., timeontask or TOT) were taken into account in its costbenefit model. This section summarizes how, in the RIA accompanying this rule, the Agency has responded to questions about the TOT analysis raised by Public Citizen and the Court in its July 2007 opinion. FMCSA's careful analysis uncovered several necessary revisions, but the net effects of these revisions are minor. Second, this section addresses the issue of cumulative fatigue and describes the Agency's conclusion, based on recent crash data and operational data, that there is no evidence that the 34hour restart provision has led to harmful cumulative fatigue.

Original Analysis

The goal of the Agency's 2005 analysis was to assess the change in fatiguerelated crash risks that would result from eliminating driving in an 11th hour of driving. Assuming motor carriers will still deliver the same volume of freight even without the 11th hour, FMCSA concluded that driving that could not be completed in the 11th hour would be completed by additional drivers in somewhat shorter trips. Crashes, including some that are fatiguerelated, will occur in those shorter trips. The 2005 RIA calculated the average fatiguerelated crash rate in trips that allow the 11th hour compared to the rate in the replacement trips that do not.

A TOT effect was added to the fatigue model by establishing a function relating TOT and the percentage of crashes attributable to fatigue, relative to typical fatigue levels, and using that relative risk to scale up the fatigue crash risk for hours with aboveaverage fatigue. The model was then calibrated by scaling the results to bring the average fatigue crash risk in the baseline in line with the rate projected for longhaul driving in earlier modeling of the impacts of the 2003 rule.

To find the relationship between TOT and fatigue, FMCSA used Trucks Involved in Fatal Accidents (TIFA) data from 1991 through 2002 (A general discussion of the TIFA data set can be found later in this IFR under section F's subheading ``Trucks Involved in Fatal Accidents (TIFA) Data''). For each TOT level from the first hour through the 12th, FMCSA computed the average percentage of crashes caused by fatigue. Few data points were available for TOT levels beyond the 12th hour, not least because it was illegal, in most cases, to drive past 10 hours during this time period. To use the limited data on fatigue percentages at high TOT levels without introducing too much variability, FMCSA pooled the data for all crashes beyond 12 hours: we constructed an observation that assigned the average percent fatigue related crashes to the average TOT for all crashes beyond 12 hours, and used this as an additional data point in the analysis. Specifically, the average percentage of fatiguerelated crashes for these crashes was 24.75 percent; and the average TOT was 16.7 hours.

A regression analysis included this combined data point and showed a clear pattern of increasing fatiguecrash percentages at high TOT levels, as shown in Exhibit 1. A cubic function fit the data well, including the final, combined point.

From Exhibit 1, it appears that the data point for the 11th hour by itself lies well above the general pattern of most of the data. In the years from 1991 through 2002 during which the data were collected, driving beyond 10 hours violated the HOS rules. There were two exceptions when driving beyond 10 hours would not have violated the HOS rules. First, driving beyond 10 hours would not have violated the HOS rules when the driver was driving in intrastate commerce under State HOS rules. Second, driving beyond 10 hours would not have violated the HOS rules when the driver was driving under the Federal adverse driving conditions \1\ exception, 49 CFR 395.1(b)(1), which by its very nature suggests a more stressful work environment at the time of the 11th hour of driving. Thus, the only drivers represented were those who were willing to violate the rules or who were exempt from the rule and may, [[Page 71253]]
therefore, have been unusually fatigued for reasons other than TOT. \1\ ``Adverse driving conditions'' means snow, sleet, fog, other adverse weather conditions, a highway covered with snow or ice, or unusual road and traffic conditions, none of which were apparent on the basis of information known to the person dispatching the run at the time it was begun.

As shown in exhibit 1, the model's predicted relative risk at the 11th hour is lower than the raw percent of fatigue related crashes at the 11th hour. This is not surprising, however, given the standard errors of the estimates at the longer driving times. There were 94 crashes in the 11th hour in the data set; even if the predicted value of about 7 percent fatigue is correct, a random selection of 94 crashes would frequently show 9 or more due to fatigue.

[GRAPHIC] [TIFF OMITTED] TR17DE07.007

Using the cubic function, FMCSA calculated the probability that a crash at a given TOT would be coded as fatiguerelated. In order to calculate the impacts of allowing the 11th hour of driving, FMCSA then had to take these results and apply them to a model of what would happen to driving patterns with and without the 11th hour provision. FMCSA used these modeling results to calculate a TOT ``adjustment factor'' to calculate a total risk of fatiguerelated large truck crashes, incorporating both TOT and nonTOT fatigue risk factors. In order to scale the effects, in the modeling, each fatigue probability for TOT levels of 8 hours or more was divided by a measure of the average fatigue probability across the first 11 hours, as seen in the TIFA data. This was simply to prepare the TOT results for use in the overall model, and is explained in more detail in the RIA. If properly performed, this rescaling should not affect the results of the analysis of each option, since the relative relationship of fatiguerelated risk to driving hours is unaffected by the scaling factor. In the 2003 model, for TOT less than 8 hours, no incremental fatigue risk was calculated on the grounds that for these hours fatigue was at or below average. As discussed later on in this preamble, the lack of adjustment for the hours before 8 biased the results, and needed to be addressed in revising the analysis.

This approach created fatigue adjustment factors. For each hour of driving that was modeled, the predicted fatigue crash levels in the absence of a TOT effect were multiplied by these factors.

This analysis was used to calculate the reduction in crash risks resulting from eliminating the 11th hour. In a model run that allowed the 11th hour, some hours of driving would fall into the 11th hour; their predicted nonTOTadjusted fatigue crash likelihoods would be multiplied by a factor greater than 1.0, based on the modeling results, which would increase the values to reflect the higher fatigue levels expected at high TOT levels. In runs that eliminated the 11th hour, the predicted nonTOT fatigue crash risks would be multiplied by generally smaller TOT multipliers, and so the predicted average crash risk would be lower than in the run that allowed the 11th hour. Using this method, and calibrating the model so that the baseline run would show 7 percent fatiguerelated crashes, FMCSA found that eliminating the 11th hour would reduce crashrelated damages by about 0.3 percent, worth about $60 million annually.

Challenges to the Analysis

In the 2007 challenge by Public Citizen, the original analysis was disputed in several ways. First, petitioners questioned the use of a function that combined the data points beyond 12 hours and treated them as though they fell near the 17th, rather than at some other point on the graph (e.g., at the 13th hour). Second, the reason for dividing the predicted fatigue levels from the TOT function by the average fatigue related crash rate was questioned. Third, the value used to adjust the total crash risk to the fatiguerelated crash risk was criticized as being based on TOT hours 111, rather than the hours 110 that would be allowed in the alternative that eliminated the 11th hour. FMCSA's responses to these challenges, and the revisions to the analysis that were made as a consequence, are explained here.

Statistical Approach. FMCSA's basic approach of fitting a function to the entire range of TOT hours rather than relying on the percentage of crashes at
[[Page 71254]]
a particular hour is a widely accepted statistical method. Relying on the percentage of fatigue crashes for individual TOT hours would subject the analysis to great uncertainty, because random factors can cause large changes in measured percentages of small numbers. The data used in the 2005 analysis, for example, shows that in the 13th hour, 25 percent of fatal crashes are fatiguerelated, while the 14th hour shows 0 percent fatigue crashes; the 11th hour shows 9.6 percent, while the 12th shows only 8.7 percent. Further, data can vary across years. For example, in data and analysis explained below, in 2004 there was not a single fatiguerelated fatal crash in the 11th hour. None of these widely varying values are precise measures of what would be seen if more observations were available. If TOT affects fatigue crash risks, it is more likely to be due to an underlying tendency to become more fatigued with longer periods of driving than to the individual effects of particular hours of driving. The need to fit a function to the data, extrapolating from the large volumes of crash experience at low TOT levels, was in fact recognized by the Court in its 2004 decision:

The mere fact that the magnitude of timeontask effects is uncertain is no justification for disregarding the effect entirely. The agency, for example, could have extrapolated the timeontask effects of driving longer hours using crashrisk data derived from drivers who drove for shorter periods of time. (Public Citizen v. FMCSA, 374 F.3d 1209, D.C. Cir. 2004, Slip opinion at 16)
FMCSA believes the use of a combined data point at the average TOT and average fatigue crash risk along with the use of a cubic function were reasonable approaches to the need to fit a function and use the limited data available for high TOT values. Moreover, in reassessing this model, we have evaluated the suggestions made by Public Citizen and found that they would have been inappropriate. Specifically, Public Citizen suggested a method by which the average crash risk shown in the data for longer driving hours could have been combined and then placed at 13 hours for the purposes of modeling. If fatigue goes up steadily with TOT, one would expect the average fatigue percentage of crashes at and beyond 13 hours will be higher than the fatigue percentage at exactly 13 hours. Thus, combining all the highTOT data at 13 hours would have biased upward the estimated relationship between TOT and fatiguerelated crash risk.

It is true that FMCSA did not use more recent statistical modeling techniques that utilize all of the individual observations of crashes across all TOT levels, but rather aggregated observations at specific hours of TOT to calculate and model those percentages. \2\ One flaw in the original approach is that the cubic functional form allows for fatigue percentages that are greater than 100 percent or less than zero, which are outside the range of possible values for fatigue percentages. Another issue is that, by combining the data beyond the 12th hour, the analysis leaves out some of the available information: for example, it does not consider the relative numbers of crashes at different TOT levels. The revised analysis, described below, addresses these shortcomings in the original approach and employs a superior statistical method for analyzing binary outcomes, i.e., whether the crash was fatiguerelated crash or not. FMCSA specifically requests comment on this new modeling approach.
\2\ In an analysis recently submitted to the Court by ATA, an expert statistician states that there is a ``reasonable basis in statistical theory and practice for FMCSA's approach.'' He has concluded that FMCSA's approach ``has a reasonable basis, in contrast with [Public Citizen's] illustrative example, which is virtually guaranteed to produce a biased result.'' The expert found that ``FMCSA's cubic regression curve matches the curves produced by more sophisticated methods quite closely over the relevant range of driving hours, in contrast to [Public Citizen's] illustrative alternative curve, which departs substantially from the curves produced by more sophisticated methods.'' Declaration of Dr. M. Laurentius Marais, Ph.D., at ] 6. See Tab F of the ATA Motion's Addendum to read Dr. Marais's declaration. It is in the docket referenced at the beginning of this notice.

In response to the D.C. Circuit, FMCSA has reestimated the function using a flexible logistic function, which lets predicted fatigue values range only from 0 to 100 percent. In this approach, every available crash data point was used, and several variants were tested to find the bestfitting logistic curve. See the RIA's Appendix V for details. The RIA is in the docket referenced at the beginning of this notice. In addition, because there are other determinants of fatiguerelated crash risk besides the number of hours driving, FMCSA also explored taking other variables into account, including time of day, day of the week, and type of power unit (truck tractors or straight trucks). Again, this multivariate approach to predicting risk is a standard statistical technique. These extra factors did not change the simple relationship of TOT to fatigue crash risk; however, there are other interesting results relevant to the restart provision we will explain further below. This approach yielded a TOT fatigue crash risk function that was generally similar to the original cubic function for low TOT levels, but lay somewhat lower at the 11th hour as shown in Exhibit 2.
[[Page 71255]]

[GRAPHIC] [TIFF OMITTED] TR17DE07.008

Division of the Fatigue Percentage by its Average. Dividing the predicted fatigue crash risk by an average value is a reasonable way to create a TOT adjustment factor that changes relative fatigue values within a set of data without changing the average value of that set. The fatigue model used in the original analysis yielded raw fatigue predictions for each simulated driving hour, but did not take TOT explicitly into account. Suppose these raw predictions happened to average 7 percent fatigue. To adjust these predictions to account for TOT effects, each simulated hour's fatigue percentage should be multiplied by an adjustment factor based on the TOT fatigue function: The raw predicted value for an 11th hour of driving, for example, should be multiplied by a larger value than for a 1st or 8th hour.

FMCSA could have used the TOT fatigue function directly as an adjustment factor: Raw predicted values for the 11th hours could have been multiplied by 0.072, and those for the 1st hours by 0.014. On average, however, the resulting values would have been much smaller than the original values, because the average value of the TOT fatigue function across all hours is less than 0.03. To return the typical fatigue value to a more realistic level, the adjusted values would have had to be scaled up by close to two orders of magnitude. As an alternative, the TOT fatigue function can first be divided by its average. This step creates an adjustment factor that averages 1.0, with some values above 1 and some below. Using this adjustment factor will take the TOT effect into account while leaving the typical measured fatigue level relatively unchanged.

Choice of the Divisor. In the original analysis, the TOT adjustment factor was created by dividing the TOT fatigue function by 2.92 percent, which was the average relative fatiguerelated crash risk level for the first 11 hours as seen in the underlying data. It was argued by Public Citizen that the average value of the function for the first 10 hours would have been more appropriate. Because of the details of the analysis, however, and the way the results were scaled, the choice of divisor has no effect on the results. As demonstrated in Appendix V of the RIA, when the fatigue adjustment factors are applied to both the baseline and policy options, the divisor cancels itself out, and has no effect on the estimate of the relative fatigue crash percentages with or without the 11th hour.

Thus, FMCSA concluded both that there is a conceptual basis for dividing the predicted fatigue levels by TOT by the average fatigue levelto create an adjustment factor centered on 1.0and also that the choice of an exact divisor is unimportant because that factor cancels out in the mathematical calculation.

Updates to the Analysis

FMCSA concluded that two issues newly identified by the D.C. Circuit needed to be addressed in revising the estimated benefits of eliminating the 11th hour. First, the function used by the Agency was not ideal. As discussed above, although we continue to believe our original approach is reasonable, we have developed a more sophisticated model. Second, the approach laid out above was implemented incorrectly. Although all TOT hours should have been adjusted, in the 2005 analysis, only hour 8 or more were given adjustment factors. The Agency has calculated how these two issues would have affected the estimated benefits of eliminating the 11th hour by estimating the change in the average fatigue crash risk twice: once with the original approach, and once with an updated approach. For each approach, this was accomplished by

Estimating the fraction of driving that was done in each TOT hour,
[[Page 71256]]
assuming that driving 11 hours was legal;

Multiplying the fraction for each TOT hour by a TOT fatigue adjustment factor;

Summing the results of this multiplication;

Repeating these calculations for a case that allowed only 10 hours of driving; and

Finding the percentage change in the fatigue percentages between the 11 and 10 hour cases.
The details of these calculations are shown in Appendix V of the RIA. Under the original analysis, the fatigue crash risk appeared to fall by almost 3.6 percent if the 11th driving hour were restricted. Under the revised analysis, the fatigue crash risk fell by 5.1 percent. Thus, correcting the TOT approach is expected to increase the projected TOT safety benefits by a factor of about 5.1 percent/3.6 percent, or about 1.42 times. Thus, if the analysis had been done correctly, the true benefits would be about 1.42 times the original estimate of $60 million, or about $85 million per year.

Comparisons of Revised Benefits to Estimated Costs

The increase of $25 million in benefits per year still leaves the projected benefits of restricting the 11th hour of driving of $85 million per year far short of the projected costs. The costs of prohibiting the 11th hour were estimated by finding the average reduction in driver productivity in shifting between a case that assumed driving time is capped at 11 hours and a variant that capped driving time at 10 hours. As described in Appendix V of the RIA, the change in productivity of almost 2 percent, valued at almost $300 million per percentage point, led to an estimated cost of $586 million per year for eliminating the 11th hour. In the original analysis, subtracting the benefits of $60 million left estimated net costs of $526 million; with the revised TOT analysis, the net costs are now estimated to be $501 million. This reduction in net costs from $526 million to $501 million amounts to less than 5 percent of total net costs. Thus, the revisions to the TOT analysis have very little effect on the estimated costeffectiveness of eliminating the 11th hour.

The RIA did present a sensitivity analysis that showed, under a variety of unique circumstances, the net costs could fall from $526 million to about $240 million. As such, the conclusion reached in the RIA accompanying this rule was that, regardless of the assumptions made, whether they were related to the percent of all large truck crashes that are fatiguerelated, the relative risk associated with fatiguerelated large truck crashes in the 11th hour, or the value of a statistical life, there would still be a minimum annual net cost of approximately $160 million to eliminate the 11th hour of driving.

The 34hour restart provision.

The 34hour restart provision gives drivers, particularly longhaul drivers, operational flexibility in planning their trips that previously was not available with the 7 and 8day limits. FMCSA set the limit at 34 hours because that would provide drivers with an opportunity to obtain two 8hour sleep periods while keeping them on a 24hour cycle. The Agency adopted the 34hour restart after reviewing studies considering the time periods necessary for overcoming cumulative fatigue caused by sleep debt. [Dinges, D.F., et al. (1997), p. 267; Balkin, T., et al. (2000), p. ES8; Belenky, G., et al. (2003), p. 11; Van Dongen, H.P.A., et al. (2003), p. 125. The research studies cited in this interim rule are included in the List of References in the 2005 final rule (70 FR 49978, at 50067). Copies or abstracts are in the docket referenced at the beginning of this notice.] As the Agency explained in 2005, fatigue resulting from sleep loss is usually characterized as acute, resulting from a single insufficient sleep period; or cumulative, resulting from two or more insufficient sleep periods [Rosekind, M.R., et al. (1997), p. 7.2]. Rosekind describes three types of sleep loss (i.e., total sleep loss, partial sleep loss, and sleep debt): ``Sleep loss can occur either totally or as a partial loss. Total sleep loss involves a completely missed sleep opportunity and continuous wakefulness for about 24 hours or longer. Partial sleep loss occurs when sleep is obtained within a 24hour period but in an amount that is reduced from the physiologically required amount or habitual total. Sleep loss also can accumulate over time into what is often referred to as 'sleep debt.' Sleep loss, whether total or partial, acute or cumulative, results in significantly degraded performance, alertness and mood'' [Id.].

Public Citizen's challenge to the 2005 rule argued that the restart provision allows drivers to work more hours each week, leading to cumulative fatigue that is different from sleep debt. In its opinion invalidating the 34hour restart the Court agreed, explaining that it was interested in a ``different kind'' of cumulative fatigue, the cumulative fatigue ``associated with the increased driving and working hours that [the 34hour restart] would permit,'' and not ``the `sleep deficit' that `accumulates with successive sleepdeprived days.' '' The Court concluded that FMCSA had not adequately considered this ``cumulative fatigue.''

This interim rule responds to this finding by the Court in two parts. First, the Agency found in 2005 that few studies address the effect of recovery periods between work periods spanning multiple days, such as a workweek [O'Neill, T.R., et al. (1999), p. 2; Wylie, C.D., et al. (1997), p. 27; Smiley, A., & Heslegrave, R. (1997), p. 14]. After reviewing the studies relevant to the 34hour recovery period, as cited in the 2003 rule and those submitted by commenters to the 2005 NPRM, the Agency determined that current scientific evidence is limited with respect to the type of cumulative fatigue raised by Public Citizen and the Court. Studies of timeontask frequently measure ``fatigue'' as a function of drowsiness. For example, Wylie, C.D., et al.'s 1996 operational study of 80 longhaul drivers engaged in revenuegenerating runs in the U.S. (under the 10hour driving limit) and Canada (under that country's 13hour driving limit), reported that timeontask was not a strong or consistent predictor of observed fatigue, measured as drowsiness, as observed in video records of comparable daytime segments of driving. In Wylie's study, no difference in drowsiness was found between 10 and 13 hours of driving. Some measures of performance, such as lane tracking and individual cognitive performance, as well as self rating of fatigue, were better at 10 hours of driving time than at 13 (lane tracking was confounded by difference in driving routes and road conditions in the two countries). Conversely, reaction time was better at 13 hours of driving than at 10. The authors noted that the lack of variance in drowsiness between driving periods may be attributable to the fact that the study measured only daytime drowsiness. Other research suggests the body's circadian rhythm limits the negative effects of more hours of work during daytime operations. [Wylie, C.D., et al. (1996) pp. 5.135.14].

A 1999 study evaluated the effects on fatigue and performance during a daytime schedule of 14 hours on duty and 10 hours off duty, with drivers performing simulated driving and loading/unloading tasks. The authors found mild cumulative effects on subjective measurements of sleepiness; a slight but statistically significant deterioration in dutyday subjective sleepiness, reaction time response, and measures of driving performance over the course of a week; but no cumulative deterioration of driver response in
[[Page 71257]]
crashlikely situations. The authors reported that a schedule of 14 hours on duty (with 12 hours of driving) and 10 hours off duty for 5 consecutive day periods did not appear to produce significant cumulative fatigue over the 2week testing period [O'Neill, T.R., et al. (1999), p. 48].

Additionally, as its second part of its response to the Court's finding, FMCSA sought recent (i.e., post2005) scientific studies addressing cumulative fatigue of the type focused upon by the Court. Although some popular literature discusses ``burnout,'' the Agency does not consider these anecdotal narratives to be evidence that cumulative fatigue is a significant concern under normal driving conditions. While the Agency concluded based on a reasonable review of the literature that cumulative fatigue associated with increased weekly truck driving activity under the conditions similar to that studied in the literature was not a substantial problem, the critics of the 2005 rule did not provide any scientific literature supporting their claims of cumulative fatigue specific to truck driving. It is therefore not surprising that FMCSA has been unable at this time to identify an available model that it could use to evaluate the effects of cumulative fatigue as a factor separate from fatigue caused by sleep deficits in a motor carrier context. FMCSA seeks existing studies or models that could be used to further analyze and validate the veracity of these claims regarding cumulative fatigue, specifically studies or models analyzing or focused on truck driving.

Furthermore, Public Citizen discussed a scenario by which the new rulemaking would allow for a substantially higher number of hours than would be found under the more normal driving conditions similar to those studied in the literature. This would be accomplished by driving 11 hours, immediately going off duty for 10 hours, and repeating this pattern.

First, although such a pattern could develop in certain operations for certain periods, nothing like this was observed in FMCSA's 2005 and 2007 Field Surveys. Additionally, nonstandard driving patterns were allowed under the pre2003 rule that had the potential to result in significantly more sleepassociated fatigue than the driving patterns that would be allowed even under Public Citizen's unlikely scenario. For example, under the pre2003 HOS rules, a driver was permitted to exclude intermittent periods of offduty time from the maximum 15 hours of onduty time, after which the driver could not drive a CMV. Therefore, a driver having several offduty periods (e.g., meal breaks, inactivity awaiting dispatch, personal business) of several hours each during the day could legally drive a CMV in the 24th or later hour after the start of the duty day. Under the current HOS rules, this driver could not drive a CMV after the 14th hour of coming on duty following 10 or more consecutive hours off duty, regardless of any intermittent offduty periods. FMCSA therefore believes the pre2003 possibilities of ``extreme'' driving behavior are actually eliminated under the 2003 or 2005 rule. FMCSA specifically requests comment on this conclusion.

Furthermore, FMCSA has conducted additional technical analysis of the Trucks Involved in Fatal Accidents (TIFA) data (referenced later in this IFR) to examine the potential relationship between the probability of a fatiguerelated large truck crash and other factors that one might expect to influence the likelihood of a fatiguerelated crash. We believe this further analysis is relevant to both the more standard driving schedules commonly observed in the industry, and work schedules where commercial drivers may be pressing the daily driving and weekly onduty limits. This is because TIFA data captures various types of commercial drivers involved in fatal large truck crashes, without regard to specific operating schedules. As such, if cumulative driving hours across a noninterrupted series of days independently caused an increase in fatiguerelated crash risk, FMCSA believes this analysis would identify it. After studying the pattern of restarts in the industry, FMCSA determined that a reasonable proxy for the time spent driving over multiple days after a restart is the day of the week. This is because the majority of restarts happen over a weekend, as revealed in the 2007 Field Survey discussed later in this preamble.

Specifically, a logistic regression modeling approach was used for this analysis and TIFA data covering the period 19912004. Several additional TIFA variables of interest were included in the logistic regression beyond the ``hours of driving'' used to address time on task (TOT) in the regulatory impact analysis (see RIA in docket for details of that analysis). These additional variables included day of the week of the crash, time of day of the crash, the number of vehicles involved in the crash, and the type of vehicle involved (i.e., straight truck versus tractortrailer combination). The additional variables made it possible to broaden the analysis of potential causes of large truck fatiguerelated crashes, which added interesting insights but did not, in the end, change the TOT analysis itself (as is fully discussed in the RIA). For instance, FMCSA modeled single and multivehicle crashes. For these analyses we excluded cases where the hours of driving were not reported, where the vehicle was government operated and exempt under 49 CFR 390.3(f)(2), or where the vehicle was a daily rental and the gross vehicle weight rating (GVWR) was 26,000 pounds or less. We fitted various logistic models to the data. Specifically FMCSA estimated five unique logistical regression models which included the following independent variables:

Model 1: Hours of Driving;

Model 2: Hours of Driving, Day of week, Time of day (0 to 24), Large Truck Type (Single or Tractor/Trailer);

Model 3: Hours of Driving, Day of week grouped (Mon, Tue Thu, Fri, SatSun), Time of day in 3hour groups, Large Truck Type (Single or Tractor/Trailer);

Model 4: Hours of Driving, Time of day (0 to 24), Large Truck Type; and

Model 5: Hours of Driving, Time of day in 3hour groups, Large Truck Type.

The dayofweek variables in Models 2 and 3 were found not to be significant and so were excluded from Models 4 and 5. The fact that fatigue did not appear to change systematically throughout the week has a direct bearing on the question of the accumulation of fatigue with long hours of work over multiday periods. Drivers of large trucks tend to take their extended breaks (i.e., restart periods) over the weekend as was revealed by the 2007 FMCSA Field Survey data discussed in a later section of this preamble. If heavy working schedules of truck drivers actually led to substantial increases in cumulative fatigue, we would expect to see driving performance deteriorate over the course of the week. FMCSA believes this provides sound evidence that drivers are not accumulating significant levels of ``time on task'' (TOT) cumulative fatigue over the course of the week.

The Agency has not identified any evidence that cumulative fatigue represents a significant problem under the 2003 or 2005 rule. As it stated in the 2005 final rule (70 FR 50022) with respect to the impacts of the 11hour driving rule and the 34hour restart, FMCSA continues to believe that ``the average driver [does] not, and cannot realistically, drive and work the longer weekly hours, on a regular basis,'' as suggested by opponents of those two provisions. It is virtually impossible for a driver to drive 77/88 hours over 7/8 days and to be on duty 84/98 hours over the same 7/8 day period. To follow the [[Page 71258]]
scenario identified by these opponents, the driver would be severely limited in his or her ability to obtain fuel and food, to attend to personal hygiene needs, to park large trucks, to communicate with dispatchers, to pick up loads, to unload, and to do paperwork. FMCSA believes this is so unrealistic that seeing this type of driving behavior during the

FOR FURTHER INFORMATION CONTACT Mr. Thomas Yager, Driver and Carrier Operations; or MCPSD@dot.gov. Telephone (202) 3664325. Office hours are from 7:45 a.m. to 4:15 p.m., e.t., Monday through Friday, except Federal holidays.