I am about to do a lighting survey of our loading bays and yard area, specifically when it is dark. HSG38 - Lighting at Work specifies a level of 20 lux where there is movement of people, machines and vehicles, but I feel this is not adequate for the task of unloading a vehicles. There is a note on the standard stating: Only safety has been considered, because no perception of detail is needed and visual fatigue is unlikely. However, where it is necessary to see detail to recognise a hazard or where error in performing the task could put someone else at risk, for safety purposes as well as to avoid visual fatigue, the figure needs to be increased to that for work requiring the perception of detail. I am thinking of applying a higher standard of lighting for unloading vehicles of 50 lux. What do others think?

The CIBSE Lighting Guide is a better starting point but I don't think it is available free anywhere. It certainly contains a lot more information. LB