Factors to consider in car seat adjustment, steering hold

The driver needs to be comfortable and alert with clear all-round vision, positioned to operate all the controls.

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What you need to know:

  • Humans vary in size and shape more than almost any other species.
  • There can be no meaningful ‘average’ human being for anthropometrics and ergonomics to design for.
  • Those outside the 150cm to 200cm physiological bracket need to find a compromise solution.

There are so many different bits of advice on the correct sitting position for a driver, and exactly where to hold the steering wheel. Is there a right answer? BSK

Yes. But it varies from driver to driver and from car to car. Confusion arises because advice usually focuses on “what” you should do, and leaves out “why”.

The essential purpose of the “right” sitting position and steering hold – for you - is to optimise your control of the vehicle; at all times and in any circumstances. Full stop.

To achieve that, the driver needs to be comfortable and alert (not crunched up or slouched), with clear all-round vision, positioned to operate all the controls – steering, pedals, gears, switch-levers and buttons - easily, quickly, accurately and completely, and without visual or physical restriction or stress.

Achieving that is a very individual setting. Humans vary in size and shape more than almost any other species – at the extremes, adults differ in height; from less than 1 metre to nearly 3 metres. The ratios between their arms, legs and torsos are also diverse, and weights range from wispy to whale. Their “comfortable” range of movement (necks, shoulders, arms, torsos and legs) also varies from creaky old crocks via athletes to contortionists. So the notion that there can be one correct driving position for all is fanciful. That’s the reason that “why” is so much more important than “what”.

There can be no meaningful “average” human being for anthropometrics and ergonomics to design for, but luckily 70 percent of drivers fall within a median range (say, 150 cm to 200 cm height), and modern seat and steering adjustments give all of those people a roughly equal chance of achieving all the “why” requirements comfortably. Those outside that generous physiological bracket need to find a compromise solution, using a different “what” but to achieve same “why”.

Power steering.

Power steering.

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An important part of that comfort and ease of movement depends on the distribution of your weight (be it light or large). You are sitting, so at least 60 per cent of it should be on your bum, partly shared by your thighs (that’s why chairs are more comfortable than benches). The balance should be shared between your back (mostly the lumbar area, only very slightly your shoulders) and on your feet. Your head should not be resting (in any circumstances) on anything other than your own neck.

To get those balances right, start with the seat squab. Adjust it so you can depress the clutch all the way to the floorboards with your left leg still slightly bent (your thigh should not have to press down too hard on the squab to reach that destination). If you have an automatic car that doesn’t have a clutch pedal, use your imagination! Then adjust the backrest so your arms/hands can reach the furthest point on the steering wheel (the centre of the steering ring, nearest the windscreen) without leaning your body forward. The arm may have to be almost fully extended to reach, but still not be stressed. The balance between that arm reach and left-leg reach can be fine-tuned by adjusting the seat squab height (as it is by design on buses and trucks that have steering wheel rings that are more horizontal…and have higher seating positions). Modern steering columns are also adjustable, up and down.

seat belt.

A driver putting on a seat belt.

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Those settings should (and hopefully will) enable easy use of all controls required for all driving operations, and your rear-view and door/wing mirrors should be set accordingly.

So-called “headrests” are a misnomer on the driver’s seat; they are “head restraints” and should only make contact with the driver’s head in the event of an accident. Set the height so if the driver’s head is backlashed against them, the centre of their cushion will hit the bump on the back of the skull. If they hit higher or lower than that, they could do more harm than good.


Car steering

Car steering.

Photo credit: Shutterstock

Where you hold the steering is also determined by “why”: so you are comfortable and have complete and precise control under any circumstances.

There are two main principles to get you started and help you make your personal decision. From observation, I have a sneaking suspicion that these are not taught by driving instructors in Kenya, nor tested by examiners. Elsewhere in the world, if you broke these rules in a test even once, you would fail. Outright.

1.Your hands should never cross from left to right or from right to left. For both(either left hand or right hand), anywhere on the other side is out of bounds.

2.Any forward turn at some speed should be conducted with both hands on the steering wheel ring, but only one hand should be doing the work – by gripping and pulling, not by pushing. The other hand should be in position, but with a very soft grip that allows the ring to feed through it.

Do I hear mumbles of “eh?” Understandably; explaining with words is more vexed than using pictures or live demonstration. But that is the principle you need to grasp…and obey. Here’s the why:

Most of us make minor steering adjustments with both hands gripping (at 9 and 3 on the clock circle; or thereabouts, according to what you find comfortable). When you turn, one hand moves upwards and the other downwards, but not very far. Both remain on their own side and almost immediately return to straight. But for tighter steering adjustments, both hands move further, and eventually will reach the top and bottom of the ring and go past the centre…onto the wrong side. I see hundreds of drivers doing that, mostly - but not always - at low speeds (junctions, parking and so on).

Again, mostly that is not dangerous. But again, not always. Once your hands have crossed, further movement of your arms is restricted. Your shoulders are no longer square to the wheel, your torso will be leaning to one side and you weight will be off-balance. If for any reasons you need to make a sudden, unexpected and even tighter turn… or go the other way… (to avoid a goat or cope with a hole or a rock or to correct a skid and so on) you can’t do so instantly or accurately. Bang!

Using the correct process of pulling with one hand and feeding with the other, you have at least one hand in a position to make a considerable additional movement (with a push or a pull) without restriction.

The key point here is that crossing your hands to some extent is not a problem 99% of the time, but using that technique becomes a habit. A bad habit. And the safer and more efficient pull and feed technique is not practiced and is not a trained and grooved reflex. Using pull and feed all the time will make it your reflex, so you are less likely to get into difficult positions in the first place, and if/when there is a surprise or emergency then your hands will be in an optimum position to handle it with competence and usually with ease.

Clearly, the amount you will need to turn a steering wheel to change direction depends on your speed and on the ratio of the steering rack in your car.

How many rotations of your steering are needed to turn the front wheels from full lock left to full lock right? On a go kart or racing car it is less than one turn – instant adjustments with minimal movement at high speed. They can go from full-lock left to full-lock right with less than half-a turn of the steering wheel. Starting at 9 and 3, their hands will never cross and need never let go or move. They can pick any angle at any moment and deliver it precisely and instantly.

On an old off-road 4WD, giving the driver lots of geared leverage for picking a low-speed route across very broken ground, lock to lock can take nearly five complete rotations. If you try to drive a vehicle with a rack like that at high speed down a twisty track you will soon need 4WD…because you will be in the ditch.

Ordinary cars are somewhere in between, with variations depending on whether it’s a sporty car, a more sedate family car, or a heavy limousine.

With power steering, liberties can be taken when making extreme manoeuvres at less than walking speed, including when reversing (for instance, you can turn the steering through much more than full rotation using the palm).