An efficient working system requires good interaction among man-machine and environment. The oil delivery truck drivers must work long hours under uncomfortable positions which make their work inefficient. The objectives of this study were: 1) to find out the seating problems of oil delivery truck drivers, 2) to study the relationship between anthropometrics of the population of drivers and the cab dimensions, and 3) to recommend the appropriate cab design. The study involves constructing three-dimensional models for the 5th, 50th and 95th percentile from a sample of 44 male drivers of the Petroleum Authority of Thailand. These were then tested with the existing cab. The subjective tests were used also. It was concluded that the existing driver cab was not appropriate for 90 percent of the population. The seat to pedal, the seat to steering-wheel and the setting height were the causes for discomfort and back pain. The recommended cab design dimension were as follows: the seat reference point (SRP) to common heel point was 52-64 cm., and the height of SRP above the floor was 30-37cm. The recommended design was found to differ somewhat from previous studies. This was probably because of the anthropometric difference.
