broad overview of public safety radio systems in usa - bands

before - radios where either low band (30-50) or vhf high band (150-170)

then UHF was added (453-460)

then 800 was added

then low band started to fade out

then 700 was added

therefore - nowadays - vhf highband + UHF + 700/800 are the primary bands in use

I think the only major user of low band now is California Highway
Patrol - plus maybe some state highway depts on 47 mhz - not sure who
though