When, during the assembly, dismantling and lifting of structures and frameworks, workers are required to access a workstation or to move around while exposed to the risk of falling into a void, the employer shall take one of the following measures:
1° Installation of a sufficient number of service ladders fixed at the head and foot, and rest landings suitably arranged;
2° Installation of gangways fitted with guardrails placed at a height of 90 centimetres and skirting boards at least 15 centimetres high, capable of being moved using lifting equipment;
3° Elevation, under the conditions provided for in article R. 4534-98, of workers in gondolas, or any other similar devices, suspended from lifting equipment.