Why are some highway interchanges lit with clusters of lights on very high poles, whereas other interchanges are lit with individual lights and poles?
Often, high volume, urban interchanges are illuminated using “high mast” lighting structures which can have a number of 1000 watt bulbs. High mast lighting illuminates a large area, which makes them cost effective for interchanges. A cost benefit analysis is often used to show the advantages of using high mast lighting. Why do some of the larger tunnels on the provincial highway system seem to have higher lighting levels at the entrances to the tunnel and get darker as you drive further into the tunnel? Also, it appears there are more light fixtures turn on in the daytime than at night. Long tunnels are illuminated with multilevel lighting zones (usually three levels plus a nighttime level) to allow the eye to adapt from the outside light levels to lower light levels. At night, this adjustment isn’t required, and the nighttime level is lower than any of the daytime levels.
