[eastforker]

I believe these trucks are used for inner city cartage or short overnight runs where the run can be made without refueling.

[thackney]

Natural Gas For Long-Haul Trucks: Which Version Makes More Sense?
http://www.greencarreports.com/news/1092467_natural-gas-for-long-haul-trucks-which-version-makes-more-sense

Natural gas becomes a fuel for the long haul
http://nccleantech.ncsu.edu/natural-gas-becomes-a-fuel-for-the-long-haul/

Naturally the pressure to switch has come down with diesel prices.

[arthurus]

Nah. This is over-the-road stuff. It makes lots of sense for big trucking copanies.