The average mainline long-haul speed of a freight train is probably around 50mph. The average speeds of freight trains are remarkably lower since trains spend a lot more time stopping (if you're dealing with local freight, you're going to be stopping every few miles to detach or attach a few train cars). Looking at <http://www.railroadpm.org/Performance%20Reports/BNSF.aspx>, the intermodal trains (which tend to be between major shipment terminals and not including local businesses) are averaging at ~30mph.