CNG fill stations run about $900,000 to $1.5 mill to install. you got to have allot of customers contracted to get these in. Otherswise you may wait for at least 6-14 hours to fill. Propane cost around $10,000 to $20,000 to install and these will fill at rate of gasoline pumps. The tanks will also give you a 90% range of gasoline vs CNG which is about 40%-50% range. It's really not feasable unless you run a long short route of about 40 mile a day. Any longer than that better consider propane. CNG has 3000psi in tanks to overcome and very heavy. Not much weight difference in propane as tanks are lighter and cost less to fill. Faster too! Not to mention the almost doubled range.