Traffic lights: double red
After reading that blog post and some forum threads about this issue, the cause seems pretty obvious to me.

At the time, the local traffic light crew had 4-light groups on hand, and didn't have 3-light groups.

This 4-light group was probably originally designed for car traffic, with one of the lights being a turn light.

If having an extra red was an improvement of any kind, it would be much more common (and likely mandatory).