Abstract

In the Region of Bad Hersfeld, Hessen, Germany a huge kali salt company harvests kali in fields from 400 – 800 m below earth’s surface. Because of the size of the area like the city of Munich they have traffic with several vehicles and machines. About 60 collisions per year happen on the roads and in the working area. In September 2021 a severe crash injured a worker. The circumstances were absolutely not clear, so the company and the supervisor authority decided to involve an accident analyst. The accident scene was about a length of 100 m in dusty conditions with many traces on the road and the walls among the scene. Darkness, high temperatures, gradients and and limited equipment because of limited transport capacities through a well were some of the challenges that had to be solved. After analysing the traces, the damages, the machine (forklift) was investigated for technical failures. Several tests investigated the engine, the steering and especially the brakes. With those information the friction on the accident road was determined. With those information, the reason for the accident was enclosed. With a gradient of almost 25% the maximum of the allowed gradient for the forklift was reached. Furthermore the friction coefficient on the road was that low, that the possible deceleration was also very low (about only 0,5 m/s²). In combination with the speed the forklift could not be decelerated in a proper way. Because of the bumpy road with some areas of even lower friction close to ice the forklift could not be driven correctly and it left the road, hit several stones, crashed into a pipeline and into large stone. The driver was hurt while his roof was destroyed by the contact with a pipeline. His positioning crosswise to the driving direction may have saved his life. 

By using 3D photogrammetry and classic instruments like a VZM 300 in combination with basic engineering knowledge this case was solved.