There are 5 channels in the MURS band that I think can be used for your purposes. It's a no license citizens band and no repeaters are allowed. It's in a pretty decent portion of the spectrum and probably should be ok for a 3 mile radius (maybe). Mobiles should work ok, handhelds, maybe not so good.
Keep in mind that MURS, whether hand-held or mobile, is limited to no more than 2 Watts TPO. In a city with tall buildings, this would be a no go for 3 miles, even with 5/8 wave antennas on the roof. In wide-open space, you could do it.