The lighting of a multi-storey car park is dealt with in the standards BS 5489: 2013 and BS EN 12464. The covered decks are treated as though they are normal interior spaces, requiring emergency illumination and appropriate signage along escape routes, which should also be clearly marked in other ways, such as having pedestrian routes painted in a different colour.
An open top deck, however, does not require escape illumination, provided that the escape route can be seen from anywhere on the open deck or as BS5489 states ‘as long as the means of egress via stairways are visible’. In practice this usually means that an illuminated exit sign is provided at the doorway leading to the stairs tower to help those who may be unfamiliar with the building structure.
This approach assumes that there is a level of ambient illumination from the surrounding area. This is often taken to mean street lighting, but there may be circumstances where that situation doesn’t really work. The top deck of the car park can be significantly higher than the street lighting, for example.
A degree of common sense should be applied. If there is a risk that escape routes may not always be clearly visible, during times of inclement weather for example, then in such instances, additional illumination, possibly including directional signage, should be provided to assist in the evacuation of the building.
This question was answered by the Lux team.