FreightWaves Market Expert Dean Croke takes a look at the subject of sleep. By providing an overview of the science of sleep, FreightWaves explains why it’s the missing component in the current Hours of Service (HOS) debate about “flexibility” – the one word that will change everything. The importance of incorporating the science of sleep into a trucking operation is also covered.

About Dean Croke: Having grown up in a family trucking business and then spending years as an over-the-road truck driver and manager of large trucking fleets, Dean has combined his practical experience with an extensive knowledge of human physiology in the development of world-class driver scheduling and sleep management programs.

The biggest issue with the entire hours of service (HOS) debate is that most people are focused on the wrong thing, completely missing the point of the process, which is to keep tired drivers off the road. If that’s really the goal of the HOS regulations, then regulating sleep has to be a core component of the current “flexibility” debate.

Why it matters: A commercial truck driver can be 100 percent compliant with the HOS regulations, yet sound asleep at the wheel at the same time. This means safety and compliance aren’t mutually exclusive, with one study showing drivers on paper logs recorded a 30 percent lower U.S. Department of Transportation (DoT) Recordable Accident rate compared to drivers using electronic logs. The difference is because paper logs afforded drivers a degree of flexibility that allowed them to schedule work and rest periods around their preferred sleep preference and sleep personality (but record something different in the log). Many safety experts say that this non-compliance is unsafe when in reality it’s the opposite from a driver’s perspective (because they actually sleep when they are tired).

The reverse is true today with electronic logging devices (ELDs). Time is recorded digitally, forcing drivers to often drive when tired and then attempt to sleep at times of the day when it’s impossible to do so (such as during daylight hours).

Exacerbating the problem are prescriptive rules including the “14-hour clock,” which prohibits driving beyond the 14th hour of work regardless of sleep and rest breaks within that time frame. Since research shows a 30-minute nap can give a driver a four-hour boost in alertness, not allowing naps to extend the workday seems illogical at best.



The physiology of sleep tells us that humans are hardwired nocturnal sleepers and have evolved to wake at sunrise and begin the sleep process when the sun goes down. Even though there are hundreds of circadian rhythms (24-hour cycles) that drive the sleep-wake process, light (and in particular blue light), is the single most influential factor in determining when we sleep and wake. To understand the power of light, think about those times when you have traveled to another country and experienced “jet lag” (you “jet” to a new time zone but your body clock “lags” behind). It may take quite a few days to adjust your body clock to the new time zone. For most people, it takes one sunrise in your new destination to move one time zone closer, so if you fly to London from New York it will take five sunrises in London for the body clock to move through five time zones.

Why the sky is blue is fundamental to understanding the sleep-wake process and why truckers are so out of sync with HOS regulations and so passionate about flexibility. The sky is blue because that’s the color that gets refracted the most. This is because of blue’s shorter wavelength bouncing off molecules in the air and scattering its light more than other colors. At sunset we see more red and orange in the sky because the blue light has been scattered out and away from the line of sight. As a result, our eyes are sensitive to blue light, which is also why you have a “Night Shift” setting on your iPhone display settings to reduce blue light at night.

To demonstrate how the timing of light impacts truck drivers, let’s look at a common situation in which drivers who work at night drive through sunrise and in the process receive the blue light signal via the optic nerve. This signal tells the body clock to begin the waking process in readiness for another day of peak activity. In this example. the drivers’ 10-hour break now starts at 9:00 a.m., which means that even though they feel extremely tired, they are unable to sleep because their brains are trying to wake them up. This is why drivers who sleep during the day only manage (on average), four and one-half hours of sleep per 10-hour block. Compounding the problem is that their sleep quality is severely diminished as “day sleep” is more fragmented and lighter in nature.

Measuring sleep in “cycles” and not hours: One of the myths about sleep is that the more of it you get, the better you feel, when quite the opposite can be the case. Six hours of sleep is better than seven, yet seven and one-half is better than six – why is this?

Human sleep follows what’s known as an ultradian cycle, in which events occur every 90 minutes – sleep cycles included. When you drift off to sleep your brain goes through various stages in succession over an approximate 90-minute period – light sleep, deep sleep and rapid eye movement (REM). Deep sleep accounts for about 75 percent of night sleep with REM accounting for the remainder, but what sets them apart is the restorative functions they perform. During deep sleep your brain is unconscious but your body is tossing and turning – you can’t hear things such as a baby crying or a heavy thunderstorm. Your body is effectively in the repair shop where the human growth hormone (HGH) is released, facilitating the maintenance and repair of bones, ligaments, muscles, skin, organs and hair. Think of deep sleep as the time when physical fatigue is dealt with.

REM sleep is quite the opposite and occurs towards the end of the 90-minute sleep cycle as the brain begins to wake and major muscle groups go into a state of paralysis so that you don’t act out your dreams. Your eyes stay active, which explains the REM characterization of this sleep stage as your eyes dart back and forth. During REM your brain is buzzing with electricity – so much so you could power a 10-watt light bulb from this stage of sleep. This phase of sleep is the mental restorative process and deals with learning, mood, emotion and memory consolidation.

You dream in all stages of sleep, it’s just that during REM your dreams are the most vivid (and at times bizarre). Over the course of a night, dreams increase in frequency and intensity with the last sleep cycle being mostly REM – that’s why your most memorable dreams are the ones that occur just before you wake.

Good quality sleep comes from getting all stages of sleep over the 90-minute period and if you’ve ever woken from a one-hour nap (the most common duration of naps for truckers) and felt worse, now you know why. When you wake at the one-hour mark you experience what’s known as sleep inertia – you feel groggy, tired, lethargic, and moody. Sleep inertia lasts about 20 minutes before it dissipates. This means your new napping strategy should include either short 20- to 30-minute “power naps” (ending just before the brain drifts into deep sleep) or blocks of 90 minutes to coincide with the end of a REM period (when the brain is already wide awake).