Many, many, liquid gas cars in Australia.
The government was even paying a subsidy to install it on cars and buses.

There really needs to be an infrastructure to be able to support this type of fuel. There are many gas stations in Australia that retail liquid gas as well as petroleum fuels.

Older Mercedes models (Carburetor or K jet models) convert quite readily to a gas installation. The best installs are gas only - no hybrid. A liquid gas powered car will suffer in the economy area by a couple of miles per gallon.

Without the government subsidy, to make a conversion worthwhile you need to do more than 15,000 - 20,000 miles per year.

Liquid gas in Australia is around 60% of normal standard fuel cost.

As far as the environment goes, Liquid gas is supposed to burn more efficiently than normal fuel however the loss in MPG compensates for the emission issues.

You can buy new factory Ford and GM cars liquid gas powered in Australia.
All main city taxis run on liquid gas.

All gas equipment must be certified and installed by a certified installer - no backyard jobs. The tank and equipment must be installed by the roads authorities every few years.

The down side is that gas conversions are done by "liquid gas enthusiasts". The resale value of a liquid gas powered car is very much less than a normal fuel powered car. Depending on the model you may not be even able to sell it.

I would not be doing any liquid gas tinkering in a home environment. The expansion rate of LNG is nearly a thousand times more than TNT. I worked at an LNG plant in Asia. We had a couple of 125.000 tonne storage tanks. Someone calculated that if by some freak accident both tanks blew up, a circle 12kilometres in diameter would be obliterated.