We have parked in sandy, gritty and muddy areas many times. Whenever we climb in through the leisure door a fair amount of debris gets left on the carpet rather than the mat. I was in IKEA the other day and spotted a cheap doormat with sticky up bristles. It occurred to me that I could cut it in to two pieces and glue them down into the driver and passenger doorwell. The idea being that as I climbed into the vehicle I could do a serious shoe wipe (one foot at a time) before I entered the vehicle. It does not get rid of all the detritus that could finish up on the carpet but at least there is no overspill off the mat.