Every so often someone asks about the street lights at the underpass at the A90 Findon junction, and why they are set the way they are.

Here is the explanation from the roads service:

“This particular underpass and indeed the one at Hillside both have a specialist lighting system in place. The light levels in the underpass/tunnel section are controlled by way of a light sensor located outside the underpass, which aligns the light level inside the area to the level outside.

“The sensor monitors the light level continuously and switches lights on and off to maintain the required level. Even during broad daylight, there will be lights illuminated in the underpass as this is when most light is required to match outside levels. As the ambient light level falls outside, the level of the light required in the tunnel reduces, so less lighting is required.