I was driving 15 miles an hour in a neighborhood and approached a stop sign. When I went to brake, the brakes vibrated, the steering wheel shook and I wasnt stopping. I pushed down harder and eventually stopped just before entering the intersection. The roads were dry and smooth, no gravel, but it felt like I was sliding on gravel or ice. This has happened several times before in rough parking lots but I thought it was just a random fluke because of gravel or a bump in the road. No sensors or warning lights came on. It happened on a Sunday so we will contact the dealership tomorrow. We have an extended warranty.