Mileage

Cecil's Columns/Staff Reports
1

In a recent column, Cecil wrote that a motorcycle uses 2200 BTUs to transport a single rider one mile, and heavy rail uses 2600.

The rail industry claims that they move one ton of freight “436 miles on a gallon of fuel,” and FactCheck.org agrees with that number.

So if my motorcycle is more efficient than heavy rail, and it weighs less than half a ton with me on it, why am I getting only 55 miles per gallon? If a motorcycle is indeed more efficient than heavy rail, and if rail can move a ton of freight 436 miles on a gallon of fuel, I should be getting, like, 800 mpg on my bike.

2

You’re comparing apples with oranges. Heavy rail moves bulk freight at 436 ton-miles per gallon. It does not move passengers at a similar rate of efficiency, because passengers prefer not to travel long distances with hundreds of fellow passengers loaded into a freight car: they like having their own seat, and some room to move around, in passenger cars.

3

But isn’t the weight of the bike plus myself simply “freight”? I’m comparing fuel used to move a certain amount of weight a particular distance to . . . fuel used to move a certain amount of weight a distance.

4

You can look at the passengers as freight, but they require more energy per ton-mile than bulk freight like coal, or goods in containers.

5

I would suspect that the heavy rail number is the mileage it is getting once it’s up to speed. If you take into account the amount of fuel it take to get up to speed, the mileage would be drastically reduced. It may even out over time - especially over long distances.

If you had an inline fuel meter and checked your motorcycle’s mileage while cruising at 30 mph in high gear on straight and level road, you probably would be getting well over 100 MPG - maybe more than 200.

6

Welcome to the Straight Dope Message Board, dohebert.

It’s always nice to mention the column you are quoting, in this case:

7

No.

The vehicle may carry freight, but as far as transportation efficiency is concerned, the vehicle itself is not considered freight. When the train folks are talking about ton-miles per gallon, they’re talking about the stuff they’re carrying - coal, grain, oil, whatever - not including the empty-weight of the rail cars themselves.

So if you weigh 180 pounds, and your bike gets 55 MPG, then your bike is able to get about 5 ton-miles per gallon of fuel. This does not compare favorably with the 436 ton-MPG figure for freight trains.

8

It should also be noted that subway cars (for instance) often run at much less than capacity outside of rush hour. So the numbers in Cecil’s article are taking into account the inefficiency of using a whole train/bus/whatever to move a small number of people (during off-hours).