PMRs (Private Mobile Radio 446Mhz)) are pants in tin boxes. These hand portables are generally light-weight, low in features, low power and low cost. They are OK for short distance 1-3 km with a good line of sight.
You'll be better off with PBRs (Private Business Radio) for in car usage.
How about a nice Havard CB rig with a K40 mag mount on the roof!!
People could also get mobiles with the PTT (push to talk) option and set them up for this purpose.