Anhydrous ammonia is lethal @ 5,000 ppm and 5-minutes exposure.The permissible limit is 25 ppm.
Overturned tanker trucks or rail cars could be potentially disastrous.
Same for an anhydrous ammonia pipeline.
There have been anhydrous ammonia explosions.
Ammonia is highly toxic,volatile,can blind,suffocate,burn,and kill.
While lighter than air,in the presence of atmospheric moisture (humidity)becomes heavier than air,settles,and displaces oxygen.
The liability of using ammonia as a motor fuel might scare off investors.Don't know.