We are all a bit different from each other and the modern car will allow for that. What the car designers are looking for is a geometric balance. This will allow as many people as possible to be able to use their vehicles. How we are and the shape of our bodies not only shapes the car but how we drive.
The first thing manufacturers will start with is the eye datum line, which is where you look. From the driver’s seat, we need a good view of the road ahead as well as the instrument panel. Having established that we can see enough to maintain safety and legality we now need free and easy access to the controls. This should be done in such a way to minimise tiredness. We now move into the territory of the cockpit drill. As driving instructors, we are aware of the effect bad position will have on our pupils and their ability to drive safely. and the first thing we want from our pupils is to be able to adjust your car properly. It is not enough to make the car just for the average person. Manufacturers want as many people as possible to be able to drive it.
Did you know? The reason we drive on the left is that we are right side dominant. Something like 90% of the population is right-handed. We traditionally keep left as this allows our stronger right arm to defend us.
This right-sided dominance gives us Port and Starboard. Boats were loaded by men lifting with their strong right arms into the left-hand side of the vessel. This left-hand side became the port side. The vessel was steered to the jetty by a paddle or a steer board on the right-hand side using the stronger right arm giving us the starboard side. You still see people in small boats steering using an oar on the right-hand side.
So the next question is why do most of the world drive on the right-hand side if we are dominant to the right and should naturally drive or keep to the left. The answer to this is two-fold and is shaped by politics and economics.
The political answer is thought to lie with Napoleon. As he conquered Europe he decreed that his armies should pass in peace. This meant they moved over to the left and instead of passing with their sword arms being able to be offered to an enemy. They showed the weaker left arm to the people coming towards them.
The next part of the answer is economic. As factories, cities and the roads grew so the economy improved and we wanted to carry bigger loads from A-B. With an old horse and cart, you could sit up top pretty much in the middle. And if anything was in front or coming toward you with your dominant right eye you could judge very accurately how much room you had and so kept to the left.
But in the USA they started to carry bigger loads requiring two pairs of horses or oxen to pull them. As there was nowhere to sit on the wagon the driver would have sat on the rear nearside animal. This is so that his right wipe hand had access to those animals to control them. When you are sat at a height and at the front it doesn’t make any difference which side of the road you are on. But if you are low and with a couple of horses in front of you to accurately judge passing you would have moved over to the right.
As our vehicles moved on from the humble horse and cart to faster mechanically propelled ones and in much greater volumes, we started to introduce a series of rules. These rules have to work for us as driver and people. So why are most maximum speed limits worldwide nearly always 70 mph (113 kmh) or thereabouts?
Besides the physics of it that says the faster you go the more room you need to stop safely, what does 70 mph limit give us? The 100-meter stopping distance is about as far as you can still see a person’s face. This means we can react to another person and we would also know that they have seen us. Hopefully, they would be getting out of our way now or we would have a chance to stop without killing them.
This ability to see a person’s face at 100 meters gives us street lamps just under 100 meters apart. At night time if you are walking, you want to be able to have some idea of the people walking around you.
The 30 mph speed limit is in place so that in the unlikely event that your car hits a person they have just over 50% chance of survival. If you drop the speed down to 20 mph that becomes 95%. This illustrates how our bodies react to speeds and impacts from cars.
We have talked about speed limits, seeing people in time and avoiding them. But what about us, the driver, how are we kept safe if it all goes badly wrong?
Besides the interior of the car being made softer to minimise damage to ourselves. We wear seatbelts. These belts are designed to work with your bones. Specifically, the diagonal should go across your collarbone and the horizontal across your hip. The important thing is your bones are solid and will, along with a properly fitted seatbelt, protect your internal organs.
Over the years cars have grown head restraints. Your head is a large lump of bone with a pointy bit at the back. This will rotate backwards unless contained by the head restraint. Not adjusted properly it could become a very real pain in the neck.
How you hold the wheel will have a very real effect. If you’ve adjusted your seat properly your arms will be slightly bent. They will be your shock absorbers. Having two hands on the wheel at 10 and 2 will prevent you twisting violently if you have to stop very suddenly and unexpectedly.
We talked about the eye. The eye itself sits in a socket which defines your field of vision. You can measure your own field of vision by extending your arms and sticking your thumbs out. Move your arms out to the side holding your head still. Stop at the point your thumbs start to disappear and this should give you a range of 180 degrees plus.
Having 2 eyes gives us a depth of vision. However, you can still drive an ordinary car with only one eye. Put your left hand over your left eye, extend your arm and thumb to the point where it disappears on the right. Now track its movement as you move right to left. Your view of your thumb to the left is now only limited by your nose.
So in an ordinary car even with only one eye, you will be aware of the width of your vehicle. You cannot drive larger, wider vehicles unless you have some vision in your defective eye. This again is so you are aware of the width of this much wider vehicle.
Inside your eye, you see with a series of receptors called rods and cones. There are about 20 million rods per eye which measure movement and contrast. They are responsible for your peripheral vision and have a limited response to colour which we will look at in a minute.
There are about 6-7 million cones which measure colour and because of their faster response to the brain give more detail. Due to this sensitivity, the eye is in continual motion building up a picture of what is happening. This is what we want our learners to do.
These colours to which the cones respond are red 64%, green 32% and blue 2% which are the primary colours. This gives us red for danger, green for safety and blue for authority. Yellow is made up of red and green. From this, we now have the colours of the traffic lights and road signs. The rods in our eyes have no response to red light. This means at night when our eyes have adapted to the dark, a red warning light is not going to wash away the rest of our vision. Because there is some response to blue from the rods we become very aware of blue lights from the emergency services.
Eyes are sometimes described as windows to the soul. A professional eye examination can also be a window to good health. These checks are capable of detecting a range of conditions such as high blood pressure. They should be done at least every two years. Remember your eyes and vision are key for driving so have a think, when were yours last checked?
