Many of the vehicles are limited in their top speed but crashes, even at moderate or low speed, often results in death or serious injury.
Since 2006 it has been compulsory throughout the EU for drivers and passengers on tourist coaches to wear seat belts.
The rules also demand that specially adapted seat belts are fitted to vehicles to protect younger children.
It is the responsibility of the driver of the vehicle to ensure that all the passengers are wearing their safety belts.
In recent years coach manufacturers have fitted three-point shoulder and lap belts similar to ones found in cars, to replace the older less effective lap only belts.
But investigators who have examined CCTV footage from the coach in Sierre believe the children on board the Belgian coach were complying with the regulations and were all wearing their belts.
Tragically the angle and speed of the impact meant that the belts offered little protection for those on board.
Olivier Elsig, the prosecutor for the Swiss canton of Valais said: “All the children had their safety belts attached. The impact was extremely violent. Everything went in each direction. Seat belts or not it did not make much difference for the children.”
Professor Oliver Carsten of the Leeds University Institute for Transport questioned the wisdom of coach trips involving children travelling late at night.
He said: “The roads can be quieter so that can help in terms of safety but it brings in the possibility of driver fatigue which can be a major factor in accidents of this kind.”