Most of us drive everyday.

We drive to and from work, do the school run in the morning and afternoon, couldn’t live without our cars on the weekends, and love heading away on a road trip during the holidays.

But why is it that driving makes us tired? You’re just sitting there, right?

Not quite. There are many reasons driving makes you feel tired. Below are some of the most common.

Driver fatigue is influenced by the time of day you’re driving

Our bodies are naturally programmed to sleep at night and be awake during the day. This cycle is regulated by our internal body clock or circadian rhythm.

As expected, your body regulates sleep at night, but there is also a spike in the production of melatonin (the hormone that regulates sleep) during the afternoon (the Spaniards have it right with their daily afternoon siesta although this practice is becoming rare in most urban areas!)

(Learn more about the circadian rhythm in this blog post.)

Driving home after a night shift

In this blog post, we refer to the two most common reasons of driver fatigue: lack of sleep, and driving at times when you would normally be sleeping. The latter refers in particular to shift workers, driving home after a long stint at work.

Nurses, security guards, and even those who work late in bars or early at bakeries are working outside of the normal 9-5 regime. This type of work often demands people to not only be awake, but work effectively against their natural body clock.

Safety at work – on the job – is one thing, but what about after a long shift when you’re driving home? The sun is rising and people are making their way to their 8am job… but you’re on the way home after a shift that didn’t begin until midnight, and driver fatigue (or drowsiness) is setting in.

You’re dehydrated or hungry

Just as you need to fill up your car with petrol before you embark on a long trip, you need to fuel your own body, too.

If you’re reaching for a sugar hit, you’ll be pleased to know it will give you a boost of energy quickly – however, that’s only temporary.

The bad thing is when that high is over, you’re likely to feel even more tired than before!

Opt for low GI foods when you’re travelling long distances in the car. They sustain you for longer as they release energy more slowly and consistently.

Where are you driving?

Long stretches of empty road – where it seems you’re doing little but driving in a straight line – become monotonous pretty quickly. Without other drivers, cyclists, traffic lights, and other road elements like stop signs, roundabouts and school zones, your route gets tedious.

This dull routine is the time where you might start to feel drowsy; you’re not being challenged in assessing your surrounds as the past 100 and next 100kms are the same. Your alertness level starts to drop as you continue down the single stretch of road, with no other cars in sight. It can also be worse if the route is familiar to you.

Additionally, sitting for long periods of time slows your blood flow as your body says, “I will save you energy”, which can put you in the mood for sleep.

Are you driving alone or with a friend?

Solo drivers don’t have the interaction with a passenger or friend to talk with, to share driving duties, or to pick up on the early signs of drowsiness. In fact, one statistic tells us that 82% of drowsy driving accidents involve a single driver.

You’re in debt. Sleep debt, that is

Most healthy adults require between 7.5 to 9 hours of good quality sleep every night. However it is a fair assumption that many of us do not reach that quota. Do you even remember the last time you felt well and truly well rested on the average workday?

It’s likely you’ve built up some sleep debt; those hours you lost when you had a late night and early morning during the work-week, combined with a late Saturday night builds up over time, leaving you with a large balance of sleep deprivation.

And the only way to pay off your debt is with sleep.

With a busy social life, family commitments and longer work hours comes a compromise to not only the amount of sleep we receive each night, but the quality of this sleep, too.

When you’re tired, your reaction times are heavily impeded, making driving feel like a draining task.

But guess what: even if you don’t think you’re tired, you can still fall asleep at the wheel

The truth is that we, as humans, find it very difficult to assess our own levels of fatigue or drowsiness.

We also have that irritating characteristic of self-confidence where we tell ourselves we are OK to drive; that we’ll be home in just a few minutes, without really understanding how drowsiness can take over our body.

What does it mean when we feel ‘drained’?

Cast your mind back to high school or university, and think about those three-hour exams you had to sit. Sure, you were seated the whole time, exerting little physical energy, but when you stepped out of the exam room, you felt mentally drained.

It’s the same as when you’re driving: you are constantly aware of your surrounds, reacting to what you see and what you hear, all while keeping your car moving at the right speed and in the right direction.

So while your body might just be ‘sitting there’ it’s responding to everything around you for every second your key is in the ignition.