Ergonomics and Automobiles Compiled by: Shilpi

Ergonomics Ergonomics (or human factors) is the scientific discipline concerned with the understanding of the interactions among humans and other elements of a system, and the profession that applies theoretical principles, data and methods to design in order to optimize human well being and overall system Ergonomics is about designing equipment and machines to our bodies and the way our body moves. Ergonomics is the investigation about humans and work. Especially when optimizing the physical contact between humans and engine.

Introduction Ergonomics in the car industry has a special meaning because comfort of a driver and his/her passengers while driving plays a crucial role in designing. Besides car performance, what really matters in industry is users' comfort and their safety. One should make sure that the interior equipment doesn't distract driver's eye attention while driving and was put in places that will not damage anybody in case of accident

Car Seats The car seat is a seat placed in a limited space, which, when in motion, undergoes dynamic forces, among which the centrifugal force plays an important role to cause discomfort. After more than a century since the automobile’s first appearance, its seats are still being designed to the same fundamental ergonomic principles Even though they are equipped with sophisticated mechanisms and endowed with the most refined padding and coverings, the seats still are defective from a comfort point of view.

Hazards Any person who spends a lot of time in a vehicle (car, truck, ambulance, etc.) experiences aches and pains. Drivers tend to experience pain more often as it is more difficult to shift body positions while driving. However, passengers also feel the same effects if they are sitting in a vehicle for prolonged periods In truth, there are many hazards related to driving, particularly in doing this activity frequently or for a long period of time. Below are few of them: Neck, shoulder and back pain Cramps and pressure points in the legs Poor circulation of blood in the legs and buttocks Lower back injury Long-term risk of degeneration of spinal disc and disc herniation

Causes Of Discomfort Sitting in a fixed posture Transference of vibration Loss of spinal support due to a poorly fitting seat Poor posture from personal habit , or from an improperly adjusted or fitted seat Shape of the vehicle seat

Risk Ergonomically unsuitable car seat or the driver’s workplace give a rise to psychophysical fatigue. Fatigue is especially hazardous when driving a car or any other motor vehicle. Accidents are probably caused by fatigue of the driver driving for a prolonged period since the body is motionless.

Drawbacks of common car seat Since the driver’s seat is adjusted to average anthropometric measurements of the human body, all persons who do not fit these measurements have certain difficulties when driving a car. Shorter drivers with shorter limbs do not only have problems reaching controls, but also in the field of vision . Taller drivers feel lack of space and reduced field of vision. These problems are reduced by correcting the seat shift, but the problem cannot be solved to the fullest. In addition, protective equipment such as airbags and safety belts cannot protect the driver with those anthropometric measures that deviate from the average ones.

What Make Seat Comfortable Generally, seats should allow our body to be comfortable and not restricted. The seat design is critical for this. The seat height should not be so high so that our legs are left dangling. The seat depth should allow clearance at the back of our knees in order to prevent pressure on the network of blood vessels and nerves.

The seat back and angle should support the natural curves of our spine (in particular your lower back). The main weight bearing should be taken by the Ischia Tuberosities (the bony parts of your bottom) and the top half of the thighs In addition, a chair should enable us to change posture at intervals, ensuring that different groups of muscles can be used for support, and that no particular group of muscles gets tired.

Analysis Of Seats Is the seat comfortable ? Is there enough headroom so you do not slouch or bump your head if the car hits ruts or potholes? Does the seat support the full length of your thighs and all parts of your back? Can we independently adjust the: seat height from the floor seat cushion angle seat back angle (tilt) distance between the seat back and the steering wheel The driver should be able to reach the pedals, steering wheel and other controls without stretching. He should have a good view of the instruments, gauges, and all mirrors, and a good vision through the front and side windows.

Analysis Of Seats Is the length of the seat cushion adjustable? There should be about 2-3 fingers width in the space between the front of the seat cushion and the back of the driver's knee. Is the seat cushion contoured to better distribute the weight on the seat and prevent or minimize pressure points on the buttocks? Is most of the seat upholstered in a breathable material (for thermal comfort)? Is the seat pan material ribbed? Will the seat and seat belt accommodate drivers who are wearing heavy winter coats or protective clothing?

Analysis Of Seats In order to minimize discomfort, the driver's seat should also offer as many adjustable features as possible. The most important ones are: Backwards and forwards adjustment of the seat, Backrest angle adjustment, Seat height adjustment – ideally independently adjustable at the front and rear of the seat, Seat angle adjustment, Adjustable lumbar (lower back) support - up/down and in/out, Headrest adjustment - vertical, horizontal and tilt. .

Anthropometry For seat design Anthropometric estimates for adults aged 19-65 (in mm) Dimension 5 percentile 50 percentile 95 percentile A. Sitting Height 850 910 965 795 B. Sitting Shoulder Height 540 595 645 505 555 610 C. Shoulder breadth 420 465 510 355 385 435 D. Hip breadth 310 360 405 370 E. Buttock- popliteal length 440 495 550 480 530 F. Popliteal height 395 490 400 445 Anthropometry is the branch of human sciences concerned with body measurements such as body size, shape and strength. This is used by ergonomists to ensure that products, such as seats, fit and suit as many users as possible. If we are designing a seat, you need to take the following measurements into account. Male Female

Seat An ergonomic design of a car seat will require data on the compatibility of human size with the car seat. The best position for driving comfort is lowering the knee at the same level as the thigh. In handling the foot pedal, the heels should be used instead of constantly twisting the ankle causing excessive torque to the vertebrae bones Sitting on a hard seat cushion will adversely affect the pelvic bone as compared to sitting on a soft foam cushion.

A high peak pressure causes discomfort to the passenger, hence poor quality of driving. Choosing the appropriate material for the seat cushion is also necessary to ensure passenger comfort. For the proposed design of the car seat, the dimension of the seat cushion is 475 x 226 x488 mm in the respective width, thickness and length.

Dimensional Consideration The distance between steering wheel and the sitting driver: dimension 1, b) Distance of the chair in XY surface: dimension 2, c) Height of the chair in XY surface: dimension 3 d) Dimensions of the length and width of placing the gear shift stick: dimension 4b, e) Steering wheel leaning angle: dimension 5, f) A driver's chair leaning angle –dimension 6. Measurements

Dimensions We must make use of norms and regulations when designing a car interior and by using them make the cabin also meet the user's needs. We should emphasize that the driver's chair – backrest should be 635mm long and the headrest – 275mm long. For passenger cars the angle of chair positioning amounts to 20° against the floor when this optimal value provides the driver a comfortable drive.

One should also take into account the distance of 76 mm between the car interior ceiling and the driver's head top. A correct distance between the chest and steering wheel should amount to 274 mm for men and 211 mm for women. The figure presents also visibility range that for both sexes should amount to 30° so that one could see a road lane and traffic lights. The steering wheel should be bent at 35° for a better comfort of a driver of a passenger car.

Correct Backrest Positioning The backrest should be upright and located forward, inside the seat and in contact with the back. The correct positioning of the backrest produces the following advantages: Improves visibility Increases vigilance Delays somnolence Makes steering wheel and  gear lever easier to control Increases space in the passenger cabin (fig.6) Comfort

The seat back rest should be high and wide enough to support the shoulders. The back rest should be shoulder-height and not interfere with rear-view vision. The seat back rest should have adjustable lumbar support. The back rest should be in contact along the full length of the drivers back. The lumbar adjustments (in and out, up and down) will enable the driver to fit the back rest to his or her back and be more comfortable.

Analysis Of Head Rest Although commonly called a head rest, it should be called a head restraint as it is designed to restrict head movement when a vehicle is hit from behind. The head restraint offers more protection when it is close to the head as the restraint will come in contact with the head faster and the contact lasts longer during a rear-end collision. A well-designed head restraint will decrease the likelihood of the neck bending backwards and causing whiplash. Is the head restraint adjustable for height and for the angle forward and backward?

Analysis Of Head Rest Can the head restraint be locked in position? If not, the head restraint may move during a collision and the driver (and passengers) may experience whiplash. Is the head restraint in the most effective position? Height - as high as the top of the occupant's head, but it should not be lower than 6 cm (about 2.5 in) from the top of the head (i.e., not lower than the height at the top of the ears) Backset - the distance between the back of the occupant's head and the front of the head restraint - the head should be as close as possible to the head restraint: an acceptable distance is about 7 cm (2.75 in) or less but it should not be greater than 10 cm (about 4 in).

Steering Wheel Bring the steering wheel down and toward you to minimize reach. The less your elbows reach forward and up the less the strain on your neck and upper back. Holding the steering wheel is also important. Instead of holding close to the top of the wheel at the 10 and 2 o’clock positions lower them to 9 and 3 o’clock or lower. Other than while turning, avoid reaching across your body to hold the steering wheel. For example, don’t hold the very top or right side of the wheel with your left arm or vice versa. Try to keep your wrist straight while holding the steering wheel.

Seat Belt The vehicle should have an adjustable shoulder belt anchorage on the B-pillar that can be moved up or down. This adjustment lets the person position the shoulder belt so that rests on the middle of the collar bone (clavicle) rather than on neck or off the shoulder. The vehicle should have an auditory signal if the seat belt is not buckled

6 Ergonomic Essentials Effective support of the legs. Proper support of the "sit bones“. Solid lumbar support. Full support of the concave areas of the spine.  Sufficient protection of the cervical spine. Proper placement of the headrest.

Recap

Conclusion One of the greatest selling features of a car is driver comfort, and the key to giving the drivers the greatest comfort and safety possible is a truly ergonomically designed car seat. Not only will the driver enjoy a healthier, more pleasant driving experience throughout the life of the car, he will also have a better test drive experience that may very well make the difference between a sale that is lost or gained. Incorporating authentic ergonomic design into the next car seat is not only good for the driver's safety, wellbeing and happiness; it's also great for the company's bottom line

Bibliography www.drivingergonomics.com Impact of anthropometric measurements on ergonomic driver posture and safety by Faculty of Automobile Technology University of Zagreb. www.ccohs.ca www.trackpedia.com www.ergonomicssimplified.com www.ergonomics.about.com

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