Years ago, when I was a cabdriver, I drove a propane
Checker taxi without any problems. The vehicle had enough range so that I could work a full 10 hour shift and drive up to 200 miles. The propane
cabs had slightly less power than the gasoline Checkers but it wasn't a big issue.
Then for many years until I retired, when I was working for the airport, I drove a CNG factory-conversion GMC 3/4 ton pickup. That vehicle had only about a 100 mile range but plenty of power. Most of the everyday vehicles (not construction or snow equipment) at the airport had been converted although some were both dual CNG and gasoline.
There's a lot of vehicles in my area that have converted to CNG--UPS vans, buses, etc. but so far it seems like it works best for fleet vehicles that stay with a certain area. I would be afraid to take a "gas" vehicle cross-county but CNG is probably already having an effect on oil imports.