Well, I'll agree with the first part of Dave222's post, but not the second.
I love rats. They're beautiful creatures who, through no fault of their own, occasionally cause problems for another species who're probably less intelligent than they are. (i.e.humans).
If somebody suggested torturing, or killing, a species like otters, there'd be howls of protest. Rats are just as beautiful and desereve our respect and proection.
So I certainly support the use of humane traps (but not the rest of Dave2222's post). Then all you need to do is to drive to somewhere in the contryside, away from housing, to deliver your new furry friends to somewhere where they can live without annoying humans. (Please, please, please, never use the standard rat poisons. They kill rats by inducing internal bleeding, resulting in incredible pain).
This is a commercial website but it offers some useful advice:
http://www.rattraps.org.uk/Rat-Traps/default.a spx
Chris
(PS: If I had your problem, my own solution would simply be to buy a supply of corn, so that I could provide the rats with a more tempting diet, well away from the spuds).