Norwegian researchers have found that good design and lighting can significantly reduce anxiety among travelers driving through tunnels, as reported by here.

The article states:

The main point is to obtain a good distribution of light, in conjunction with the use of artistic lighting, which turns out to give drivers a feeling of space and of greater security. Modern lighting systems, with two rows of lamps, light sources that illuminate the opposite direction and driving lane, are beginning to be quite common in new Chinese tunnels, and they have also been installed in the tunnel that forms part of the ├śresund Link between Denmark and Sweden.