I find that very few folks monitor .520 simplex any more. I travel a lot and have an easily recognizable ham radio setup that spans all of HF on through to UHF. It is hard to miss my truck LOL.
With all of that, I can only think of 1 or 2 highway QSOs in the last 10 years.
What I have had great success with was whatever state I am in and their 80 or 40 meter frequency. Like here in Wyoming, we use 3.9235 as a statewide chat frequency. It is non dependent on repeaters and it has great coverage.
Just a thought,
WM