This is why some lights on Highway 417 are purple

CTV’s Peter Szperling explains why some lights on Highway 417 are purple.

Driving across the city along the Queensway, you may have noticed some of the overhead streetlights are purple – but are they supposed to be that way?

You may be used to seeing amber or yellow overhead fixtures lighting up the road, or some that appear white, but in certain sections of Highway 417 in Ottawa, the lights are giving off a purple or strong dark blue hue.

It’s not by design.

“The colour of the streetlight is a manufacturer defect and not a new lighting colour,” Ontario’s Ministry of Transportation says.

In an email to CTV News, the province says, “The ministry has been in contact with the manufacturer to coordinate the replacement of the fixtures.”

Why are the lights purple?

“It starts out the LED itself is blue, and to make it look white, it’s got a mineral in front of it. And under the intense light, that mineral can break down,” says Robert Dick, a retired University of Ottawa and Carleton University professor.

“You put a mineral in front of it called phosphor that will convert some of that light into it make the light look white. By changing the amount of phosphor, you can change the shade of that white light so it can actually be rather warm, or it can be intensely white. But over time, that phosphor can degrade and as a result, more the blue light gets out and we see the light’s turning blue.”

The issue is not unique to Ottawa. There are reports of similar purple lights across North America, including in Vancouver.

Driver reaction

Some drivers who spoke with CTV News Ottawa say they actually prefer the purple hue.

“I think they should do the whole highway like that,” says Phil Begin. “I think it’s easy to see at night and it’s almost a nice, calm, soothing light.”

“At night when you get the snow coming down, you can actually see better,” says Mike Bertrand.