Full alertness

Sleep asks for little, the body clock pushes towards the day. For once, the two forces pull together.

Sleep has two forces. The first is the need for sleep: it grows with the hours spent awake and clears with sleep (the adenosine of episode 09). At ten, after a full night, it is at its lowest point of the day. The second is the body clock, which keeps us awake by day and pushes us to sleep at night: at ten it is rising. At night the two forces add up against the driver (episodes 03 and 04). In mid-morning they add up in the driver's favour. It is the widest window of the day.

After waking, the brain takes two to four hours to get going. By ten, we're there.

Right after waking we are not immediately clear-headed: that is sleep inertia, and it fades slowly. Those who measured it on three consecutive days, in people getting up at their usual time, saw that it takes two to four hours to get back to full capacity; the feeling of being awake comes first, readiness later (Jewett 1999). Getting up, showering, having breakfast, switching on the light: none of it shortened the process. Whoever leaves at seven is still driving inside the inertia. By ten it is long gone. That is why the first trip of the morning is not the best one, even after a good night.

Without a night's sleep there is no peak. Not even at ten.

The two forces pull together only if the night has cleared the need for sleep. Those who sleep little carry it through the day too, and the clock alone is not enough to cover it. Two weeks of six hours' sleep a night left readiness at the level of one or two nights without sleep; and the people living it said they felt only a little sleepy (Van Dongen 2003). It is the trap of episodes 08 and 09: the sleepiness you feel and the sleepiness that is there do not match. The ten o'clock peak is made the night before.

If you can choose when to leave, leave now. If you can't choose, at least you know.

The motorcyclist on the lake road has nothing to prove: he chose the hour. People who drive for a living often cannot choose: shifts, deliveries, timetables. Knowing the curve helps both. The first, to put the long trip in the good hour; the second, to know in which hours he can ask more of himself and in which he must stop (episodes 05, 06, 16). The motorbike is this episode's vehicle because it forgives a distraction less than anything else, and because at ten on a sunny day it is the most honest picture of full alertness.