CLEAN : Coach driver in French pensioners crash was heroic police

The transcript describes a heroic bus driver who saved passengers before a bus caught fire. Another citizen also helped by breaking a window to rescue people. The accident involved a bus colliding with a truck on a narrow, wet road. Authorities from the Gendarmerie Nationale are investigating to identify victims. The road was in good condition but was narrow and wet with possible foliage, contributing to the accident.

What is the objective of the criminalistics research institute that is arriving?

What factors might have contributed to the accident according to the text?