Red means stop, green means go, and yellow means caution. We know what these colors mean on stop lights, but what about the shapes on them? Here in the U.S., traffic lights haven’t changed much in the century since they originated. But in other parts of North America, things look quite different. Instead of our familiar trio of circular lights, Canadian provinces such as Quebec and Prince Edward Island rely on a different light layout. There, drivers might see squares and diamonds incorporated into the signal design.

These lights — laying horizontally with two red squares, a yellow diamond, and a green circle directing traffic — are supposed to help people with color vision deficiencies better tell the difference between stop, caution, and go signals. Here in the States, our vertical orientation makes it easy enough to know the top light is for stop, the middle light is for caution, and the bottom light is for go (Syracuse’s one upside-down signal aside). But in places like eastern Canada, where horizontal signal layouts are more common, it’d be a lot harder to tell how the traffic lights work. That’s where the shapes come in.

In this system, red is represented as a square, yellow is a diamond, and green is a circle. In some parts of Quebec, you might even see two red squares, one on each end of the signal, to reinforce the stop command. It’s really pretty intuitive, but it’s also starting to be replaced.

Some Canadians can recall first seeing these multi-colored, multi-shaped lights go up as far back as the 1970s. However, residents report that these special traffic lights are gradually being phased out in favor of standard circular ones. There’s no denying the conventional round design is more common. By going against the grain, these Canadian regions could actually be doing more harm than good.

While we didn’t find any data that would indicate these lights were putting people at risk, they can confuse international tourists and even fellow Canadians from other providences. At a certain point, it becomes a matter of basic math: As many as 2.6 million Canadians live with color vision deficiencies, but there were over 61 million visits to Quebec’s top tourism destinations in 2024 alone. While this system can help people with color vision deficiencies, the risks may outweigh the benefits.