People should learn hilchos mesirah in Shulchon Oruch before commenting; this is not something determined by feelings, but an actual halocho subject, just like hilchos shabbos.
If someone is causing you harm, e.g. by blocking your driveway, and you have made a reasonable attempt to get them to stop doing it and failed, you are permitted to call the cops, <i>so long</i> as your intention is not to have them punished but merely to have them stop the harm, e.g. by moving their car. So if 311 is going to send a tow truck you may call them, even though you know the person will also get a ticket. But if your <i>intention</i> is for them to get the ticket then it is mesirah and not permitted.