I love the stories about units blowing up and things but except for the fact that a propane vehicle can not go into underground parking they are as safe as any vehicle. The liquid when it turns to a gas, freezes and dissipates, it takes an exact percentage of gas to air to explode.
Gm sold a bunch of the pick-ups in Edmonton, in 1981, when the price of oil dropped and a bunch of companies went broke, they were brown step side 1/2 tons all propane. made as a propane engine no duel fuel BS.
Freightliner sells Natural gas class eights as does Peterbilt. The tecnoligy was developed in Port Kells B.C. at Westburn in Cummins engines.
The only thing needed is a distribution network,