A co-ordinated design approach was essential to account for tunnel curvatures and to avoid clashes with other essential services such as the large ventilation fans. The lighting calculations ensure that luminaire photometric performance is fully optimised and in close correlation to BS5489- 2:2008 luminance reduction curves. The design for the Conwy Eastbound and Pen Y Clip tunnels adopts a linear approach with luminaires arranged about the centreline of the carriageway. In the Penmaenbach tunnel the new lighting is side-mounted to avoid the existing centreline lighting. The interior tunnel lighting is provided by Philips T-line LED luminaires spaced to provide constant longitudinal lighting. These are controlled via two fixed dimming stages between night and day driving conditions.