We used to have dual fueled cars here, but the taxis slowly got switched to LPG only. Drivers wouldn't use the gasoline often enough, and things would get gummed up. And, this was before computers were commonplace - just a switch. LPG here is almost dead in the water, which is unfortunate. It was a tossup to convert my F-150 to a small four barrel or to LPG, with the ridiculous factory setup not working well.
I haven't seen a factory LPG vehicle here for a long time. Ford, too, had the last one here.