I got a 2005 Citroen C4, the STOP light is basically check-engine. There’s a SERVICE light for warnings, but STOP is the one that’s gonna light up when you’re overheating for example.

They are pretty popular in Europe where people bike more and small hatchbacks are everywhere and don’t have roof racks or trailer hitches. It just attaches itself to the hatch and it’s easy to take down.