I l l ANALYSIS AND SIMULATION OF A LOGGING WEIGHBRIDGE INSTALLATION

Queuing theory and simulation methods were used to quickly and inexpensively estimate waiting times at a forest industry weighbridge system. Arrival, beginning, and finishing times of trucks were measured over 2 days. Inter-arrival times were exponentially distributed, allowing the system to be approximated by a simple queuing model. Estimates of queue waiting times agreed well with observed values. The models suggested that if a second weighbridge were installed it could save over 50 hours of truck time per day. They were also used to demonstrate that the system then in use was operating at close to its maximum capacity. A simulation model written in GPSS validated the approximations that had been used to fit the queuing formulas. The simulation also demonstrated the difficulty of estimating mean waiting times accurately by observation, in systems where the traffic intensity is high. There may be other areas in forestry research which would benefit from similar analyses, probably leading to increased efficiency