As part of a study commissioned by Transport Quebec aimed at evaluating the impact of commercial vehicles on the safety of railway crossings, the acceleration performances of various heavy vehicles (buses, straight trucks and tractor-trailer combinations) was measured. The goal of these tests was to identify the typical worst acceleration performances of classes of commercial vehicles used in the calculations of sight triangles at railway crossings.
A total of 21 commercial vehicles were subjected to testing on test track facilities and on nine railway crossings representing typical configurations found in North-America. Results were used to develop a heavy vehicle acceleration mathematical model according to the vehicles' technical specifications. The acceleration performances were then combined with various criteria associated with driver perception-reaction times, and also driver performance and skill during gear shifting. Safety factors were also applied to driver performances in order to better reflect real world situations.
The overall typical performances obtained were used to calculate the railway crossing minimum sightline distances or sight triangles, according to the class of commercial vehicle, the safe clearance distance over the crossing, the possibility of changing gears, and also the roadway profile on the approach and exit of the crossing. This procedure can be adapted to commercial vehicles of all configurations, weights and dimensions, all operational characteristics, all road conditions, and all train and vehicle speeds, under normal weather conditions. This tool thus permits the calculation of sight triangles and integrates well into Transport Canada' RTD 10 Grade Crossing Regulations.