I once was a passenger in a clown car squeezed full of people who were all high as kites, including the driver. We were bowling merrily along, when someone said, “How fast are we going? I feel like we’re going really fast.” There was a bit of discussion about how fast we should be going, and whether it felt faster than that, and then the driver thought to check the speedo. 25mph, in a 30mph area. I haven’t laughed so hard since.

So yes, it can impair your judgement when driving.