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Flaws in Ergonomisc for Heavy Duty Truck Cabins

Abstract: the purpose for this article is to raise awareness among hevy vehicle manufacturers to the mistakes that are made in design and ergonomisc of their producs. Also ,it is a cumulation of needs that the modern long haul driver has.Keywords:.ergonomics , long haulage ,trucking.1. INTRODUCTION

In the field of road transportation, very important factor amongst heavy duty truck drivers in choosing a certain vehicle is represented by the comfort that can be provided for the user. In spite of the general opinion that one such job presumes a lowered degree of physical effort, real situations show the contrary. Truck drivers that are used to work related issues often accuse both physical and mental fatigue due to long working hours and an improper seating position or poor ergonomics of the entire cabin.

Moreover, it is habbit for truck drivers to spend their free time within the cabin, or even sleeping in the accomodation provided, thus making the choice of the cabin critical for the good development of their work day.

Thus, an thorough study of the problem is necessary, leading to the following study of their habbits and most common situations faced.

2. COMMON PROBLEMS WHEN DRIVING

First order of bussiness that must be taken into consideration is the size of the cabin itself. So, once a complete study of the type of transportation that is needed to be done with said truck, the cabin will be chosen accordingly, with the right size and fittings. the range of cabins on the market vary from short cabs, for day use, fitted with only two seats and generally with a raised middle section between the two, to local and national distribution cabins, which are considered day cabins still, but which have a small bed behind the two seats for occasional periods of resting, mainly when the driver has to spend the night on the road, and needs to sleep somewhere. The most common type of cabin is the one used for international transportation, type of job that implies driving for long periods of time, generally more that 7 working days is the so called night cabin, which are more generous in inside space, have two full sized beds behind the driver's seat and, occasionally purpose made areas for day to day activities.

Fig 1. Types of cabins available

It is for this type of cabins where the first fault in ergonomics can be found, more specifically in the middle section of the cabin that is, in most cases, raised and does not provide a flat, accessible space. Such mistakes are made because the main focus in designing a cabin is to have a low ceiling, which translates into good aerodynamics which, in result, turns into good fuel economy. Such structural modifications has a very negative effect on the possibility that the driver can adjust the driving position in correlation to the speed of the vehicle, road conditions, thus resulting in excessive fatigue and loss of concentration. A simple solution for the problem in hand would be raising the level of the entire cabin floor and shaping it's upper side in correlation to the aerodynamics involved. Also, some modifications are required to the placement of the two beds, that are generally one above another, more specifically lowering the two to cabin floor height.

Fig 2. Aerodynamic cabin

Another issue that must be taken into consideration from the ergonomic point of view, is the placement of the gear lever, which, in general, is placed directly on the floor of the cabin too far back for the position of the driver's seat. This situation results in poor accessibility to the lever and poor operability, correlated with the need of frequent use may cause muscular akes along with back injuries to the driver. These happen especially when tackling rough road surfaces while having very heavy loads.

Fig 3. Placement of the gear lever

One solution to the problem could be placing the gear lever on the central console, which will considerably shorten the size of the lever and the necessary maneuvers for operating it. Another big plus of this solution would be the fact that the driver will have sufficient space in situations when he needs to move around the cabin or when taking breaks from work related activities.

Whilst moving, when the driver has to be able to be focused, he must not be distracted by other elements or components that he must use. Some switches or buttons, such as the ones for the radio or CB functions, are flawded from the ergonomists point of view, because, while operating, they distract the driver from the main focus, driving. one of the most frequent operations that a truck driver does while driving, is operating the CB radio functions of the truck. This command unit is placed generally above the windshield on the driver's side. Along with the movement needed to take the microphone from it's dock, it generally results in distraction of the driver from the road conditions, a very dangerous situation if operating a heavy duty tractor truck.

Fig 4. Placement of the CB radio commands

The simple solution would be integrating such functions into the stereo system and placing the commands for it on the steering wheel. This will result in more space in the cabin, because there will be no more wires going across the windshield. Furthermore, because the microphone will be installed in the ceiling of the cabin, the function cab be used even when the driver is in one of the beds, resting, without him having to leave the bed.

This improvements that can be made with minimal costs to the production of one new vehicle are the most important ones that can make a difference for the driver while driving.

3. COMMON PROBLEMS WHILE IDLING

Taking into consideration the periods when the vehicle is stationary, there are some elements that need improvements and that will result in lower risks of injuries and improved comfort.

Fig 5. Resting areas

It is a very well known fact that a well rested driver is more prudent while driving and is the main focus point when attempting to achieve good fuel milage. This means that one of the most important areas for resting will be the bedding area.

Fig 6. Ergonomic resting area

Nevertheless, manufacturers fail to come up with efficient solutions for placing and operating the two beds, that, most of times, are placed one above another and have folding mechanisms. While for the lower bed big improvements can not be made, the upper bunk is generally hard to reach and to get into or out of. The bed is generally placed at a height of over 1,3 meters and does not have any system of ladder. A cheap solution, along with the ease of implementation, would be placing folding steps into the lateral wall of the cabin, or on the central console. The space between the door and where the beds start would be more than enough to accomodate such steps. As for the central console, the material of which is built is easily strong enough to support most drivers. Another very elegant solution would be making a mechanism to fold the upper part of the driver's and the passenger's seat to fold and create a surface that could help with access into the bedding area. Such simple solutions could greatly reduce injuries that happen when trying to get into or out of beds and especially when the driver has not an athletic posture or necessary skills.

Fig 7. Access to bedding area

Turning the focus on the resting area, several flaws in design can be found as well. While sleeping, in cold external weather, the driver needs to stay warm. This is done with the help of a night heater that generally can be operated from the dashboard. As a result, the driver has no control when in bed. The simple solution could be fitting the cabin with a system that can mentain a steady temeprature, set previously by the user. This way, once the driver has chosen the right climate for the interior of the truck, he can rest without having to adjust according to outside temeprature's variations.

Another problem while in bed for the driver is operating the stereo system of the truck. It is a pleasurable way of spendinf one's free time, and drivers often fall asleep in their beds with the stereo turned on. The most simple solution to this problem would be fitting the cabin with a remote control for all de functions such as radio, navigation or illumination.

Another area where the heavy duty truck driver has to operate is in the close proximity of the truck, where they must be able to reach storage spaces for tools and auxiliaries. They have to do daily checks to the tires, semi-trailer, body of the truck, oil or couple semi-trailers.

Fig 8. Acces to storage spaces

In some cases, these storage spaces are placed between the steps made for accessing the cabin. These steps are made from steel and are very deep into the body of the cabin. This results in very small angles for accesing she storage spaces. The ideal solution for this problem could be placing storage spaces far back in the outhern body of the truck, as access pannels that can be oprated both from outside the cabin and from the inside. A mandatory requirement for these storage spaces would be to never exceed the average driver's shoulder's height of 1,5 meters.

4. CONCLUSIONS AND DISCUSSIONSDifferent Positions of a manikin inside the cabin

are shown in the picture below:

Fig. 9 Manikin sitting positions

The figure 9 [1] shows the driver in sitting position while driving. The manikin, that was chosen for the analysis is of 50th percentile. The data those were considered are of drivers anthropometric data.The upper berd can be folded at that time and thus four people can sit in the cabin including driver. The figure 10 [3] shows the sleeping position of the people in the cabin. Arrangement for sleeping is made for two people. There are two beds, lower bed and upper bed. The upper bed is hold by chain hanging from the top.

Fig 10. Manikin sleeping positionREFERENCES[1] Dalela, S. (1999). Text Book of Work Study and

Ergonomics. University of Roorkee, Roorkee. 5th

Edition.

[2] Hedge, A. (2000). RULA Assessment worksheet.

Cornell University. Ithaca, NY.

[3] Bots, H., Buffinga, J. (2000). Design Patterns in

Automotive Design: A Behavioral Study. Technical

Report IDE 350.Author: Radu Apostu Master student at the Faculty of Aerospace Engineering, Descriptive Geometry and Engineering Graphics Department, Bucharest. Email: integrale_awd@yahoo.com

Flaws in Ergonomisc for Heavy Duty Truck Cabins

Radu APOSTU

MAY 2011 ( JIDEG

JANUARY 2012 ( JIDEG