CSX, a freight rail company, is proud enough of their carbon performance that they want everyone to know about it. They have provided two carbon calculators so people can compare transportation methods. A web address for their simple calculator is www.csx.com/index.cfm/responsibility/carbon-calculator-v2e/, and a link there goes to the more advanced calculator.
We entered information for a shipment of 100 tons of calendar roll paper, which is quite bulky and light, from Rutland, Vermont, to Miami Florida. The shipment would take five rail cars or twenty trucks.
According to the calculator, the distance is 1663 miles by rail. Sending the shipment the whole distance by train would put 4 tons of carbon dioxide into the atmosphere. At seven miles per gallon, if we shipped by truck instead, there would be 48 tons of carbon dioxide emitted.
In fairness, we have to point out that a different load would produce different results. Old newspapers, for example, are much denser, and so a hundred tons would fill far fewer cars or trucks. The calculation of the trip for rail produces the same 4 tons of carbon dioxide, but the truck transportation produces 13 tons.
Comparisons for passenger transportation are much more complicated. The reason for this is that freight is transported when it can be, but buses and passenger trains have to follow schedules and are very often not filled. In general, it is safe to say that public transportation is more fuel-efficient and less polluting than cars.