Monday, May 12, 2008

Update on transit efficiency; best case scenarios

Numbers came out for both public transit and the school bus in the local paper, and so here's an opportunity to take a look at the "best case" for transit; here defined as cases where the "empty bus" syndrome can be minimized by housing buses in the suburbs (fewer empty outbound buses in the morning) and by forcing passengers to ride (school buses). Here are the numbers.

Southwest carries about 1 million passengers per year, spends about $8.5 million in their budget, and uses about 316,000 gallons of diesel fuel as well. Last year, they had about 700,000 passengers, but used about the same amount of fuel. So far, so good; about 0.3 to 0.45 gallons of fuel per passenger to go about 17 miles on the average--from Eden Prairie to Minneapolis downtown. This would indicate effective mileage of about 35-50 mpg, beating most passenger cars. Pretty good, right?

Not so fast. First of all, if your car were diesel, you'd get ~30% better mileage--35-50 mpg is not out of the picture to begin with. You also need to drive 1-3 miles the wrong way to get to the bus stop--you only make it about 15 miles to your destination, and this doesn't count energy use in transit offices.

And the cost? $8.50 to $10 per ride, and that doesn't even count a lot of the infrastructure needed. Again, it's about the same cost as driving, and it won't even get you to a lot of places you want to go.

Now the school buses; the district has about 8000 students, of which about 5000 ride the bus each day (my estimate). The buses burn 1100 gallons per day, and most students are no more than three miles from school. Hence, the "mileage" for each student is a modest 6/.22 ~27mpg. If every parent drove their children to school--assuming some families with multiple children--it would actually burn less fuel, would produce less pollution, and would greatly reduce road wear.

It would also save them a lot of time--the paper noted recently that their GOAL was to reduce commute time to less than an hour for the average student. For most kids, it would literally be quicker to walk to school.

When you look at it, transit isn't about the environment or reducing oil use. It's about control.

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