A rat ran under my car a couple of days ago and somehow missed the wheel. I live in a rural UK area backing onto native woodland and see them quite often (indeed I've spotted the occasional rat, shrew, vole and mouse in my garden). They are quite harmless as these are the wild species. The local cats do the work of keeping them in check.
I just make sure that all potential entry points into the home are kept sealed. The only instance I've had of one getting in was a vole some years ago and I gave up trying to catch it. After a few days the poor critter was found dead on the floor of the study.