Click for next page ( 9


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 8
8 Local night routes and cross-country routes often involve SLEEP DISRUPTION nighttime driving and daytime sleeping. Night drivers com- monly shift to daytime schedules on weekends or days off, Interruptions to or disturbed sleep can make returning to resulting in weekly disruption of their usual sleeping period. sleep more difficult. It has been shown that both the number HOS rules can require an off-duty period that is not conducive and timing of disruptions can adversely affect daytime alert- to sleep (e.g., 4 p.m. to 2 a.m.), resulting in low-quality sleep ness. Some general factors that disrupt sleep in commercial immediately followed by a driving period beginning during transportation operations include a "low" circadian period (i.e., 2 a.m.). Noise, vibration, movement, uncomfortable temperature, and poor air quality in sleeping quarters; Changing or Rotating Work Schedules Unfamiliar environments away from home with less than optimal conditions; and Many commercial transportation operations require fre- Attempting to sleep at an inappropriate time for one's quent changes or rotations in schedule. These schedule shifts circadian rhythm. lead to relatively quick changes in the time of day at which operators can obtain sleep, generally resulting in inadequate INADEQUATE EXERCISE OPPORTUNITIES levels of rest. Changing or rotating work schedules can be characterized as follows: People who exercise regularly have fewer episodes of sleep- lessness. Isolated exercise, while not an effective countermea- Changes in work and rest schedules that do not have a sure for immediate fatigue, can improve sleep quality by fixed pattern and thereby result in fatigue management promoting smoother, more-regular transitions between the challenges that are extremely difficult to address, and cycles and phases of sleep. Moderate exercise lasting 20 to 30 Rotating schedules that have fairly systematic shifts in minutes, three or four times a week, promotes sleep. Exercise the work start and stop times. in the morning or afternoon is preferred, because exercise close to evening bedtime can disrupt the onset of sleep. A brisk walk can be very beneficial, although more vigorous exercise has Unpredictable Work Schedules been shown to provide increased health benefits. Even exer- cises designed for environments with restricted space (e.g., The amount of advance notice commercial transportation inside a truck sleeper berth) have also been shown to be bene- operators receive regarding their work schedule varies sub- ficial. Factors that may limit exercise opportunities include stantially. An unpredictable schedule can lead to forced changes in sleep times and therefore to low-quality sleep. Personal habits that might need to be overcome in initi- Unpredictable schedules can also cause workers to wake ating an exercise program, sooner than necessary in order to check in with dispatchers. Work schedules that might need to be adjusted to Conditions commonly associated with unpredictable work include appropriate exercise opportunities, and schedules include Travel or living conditions that can limit access to exer- cise equipment or space. Being "on call" for work without a fixed schedule; First-in, first-out work pool scheduling; and POOR DIET Schedule delays resulting from equipment, weather, or traffic problems. What one eats can be a determining factor in sleep quality and duration. Some dietary behaviors that can disrupt sleep include LACK OF REST OR NAP PERIODS DURING WORK Eating heavy or spicy foods just prior to bedtime, which can interfere with sleep by causing heartburn; Taking a brief rest or nap during a work period is a con- Consuming alcohol just prior to bedtime can induce troversial topic in some transportation settings, while it is sleep initially, but tends to lead to fragmented sleep; and considered the procedural norm in others. Research has demon- Consuming caffeine within 4 to 6 hours before bedtime strated the value of planned napping to supplement main can delay the onset of sleep as well as disrupt sleep. sleep obtained and to temporarily restore alertness on the job. Lack of rest or nap periods can result from ENVIRONMENTAL STRESSORS Company policies that restrict or prohibit napping, and Several environmental factors can adversely affect a com- Unwillingness of operators to take naps. mercial transportation operator's level of alertness. These

OCR for page 8
9 include environmental aspects related to heat, humidity, cold, Drivers should be aware of the effects of high altitude, altitude, vibration, and noise. and, if at all possible, should avoid sleeping at high altitudes (e.g., above 5,000 feet). Heat and Humidity Whole Body Vibration Generally, one experiences high ambient temperatures as dry heat (temperature above 85F, humidity less than 50%) or Whole-body vibration and acceleration accompany opera- wet heat (temperature above 85F, humidity above 80%). All tion of several types of transportation vehicles, including air- excessively hot conditions make operators feel less alert and craft, helicopters, large trucks, buses, trains, ships, and small generally more fatigued. Hot-wet working conditions can be vessels. Operation of helicopters, automobiles, trucks, and significantly more detrimental to worker performance than can buses exposes operators to increasing acceleration magnitudes, hot-dry conditions and will usually make one feel "fatigued" with a frequency range extending up to 100 Hz, depending on much sooner than will temperatures less than 75F. the roughness of the air/road/seas and the vehicle speed. Although most operators consider these to be lower-level Cold fatiguing effects, they can add to operators' general feeling of fatigue, thereby compromising their alertness while oper- Cold weather can indirectly contribute to operator fatigue. ating equipment, especially if they are exposed to these effects Operators often wear several layers of clothing during cold over long duty days. weather, which can make using restroom facilities more dif- ficult, which in turn can lead operators to reduce the amount Acoustical Noise of liquids they consume. Reduced liquid consumption can then lead to dehydration, which can cause operators to Operators are exposed to engine noises in all transportation become fatigued more quickly than usual. vehicles, as well as related noises emanating from controls, transmissions, braking systems, and wind streams. Some of High Terrestrial Altitude these noises present more of a hearing-conservation issue than a driver fatigue issue. In fact, wearing ear protection in the Driving at altitudes in excess of 5,000 feet can increase a presence of these noises is often called for; however, these driver's respiration and heart rate; and sleeping at high altitude noises can also contribute to an operator's level of fatigue. The can result in blood pooling in the arms and legs. Spending continuous "hum" and other intermittent noises of most run- even a few hours at high terrestrial altitude (e.g., mountainous ning engines, especially in hot and stuffy crew compartments, passes) can cause the general malaise and discomfort that can contribute to sleepiness on lengthy trips. Being aware that accompanies Acute Mountain Sickness (AMS). These effects noise can contribute to one's overall feeling of operator dissipate as one acclimates to a higher altitude, usually in a fatigue is an important step toward ensuring that operators matter of a few days. take rest breaks.