As you may know, I have a bit of a hobby/obsession: warning people when their brake lights are out. This morning I had a two-fer; I jumped out of the Jeep in a parking lot to alert a woman that both her reverse light and CHMSL were out.

Anyway, last night after a discussion with a different driver about her lights, I had a revelation, and I’m curious whether anyone knows whether I’m correct.

Every once in a great while I’ll notice, as I did last night, that one running light is brighter than the other; effectively, the brake light is on all the time when the lights are on.

It finally dawned on me, too late to bring the idea to the attention of the other driver, that this may be by design: that if the vehicle senses one running light is burnt out, it’ll redirect the power to the brake bulb.

Anyone know whether this is a thing?