I currently drive 90 miles a day in my battery-powered SUV. I wouldn’t characterize it as a high-tech golf cart. It is a useful, clean, and quiet form of transportation. Although I have to admit that I don’t cruise along at 80 mph — the speed limit is 70 mph for the largest part of my commute.
Are you talking about this article? It’s customary to put a link to the article you’re referring to in this section. It also seems customary that the first reply also reminds the OP of that fact
In Cecil’s article Is mass transit a waste of energy?, he says
Don’t some subways use light rail trains?
Also he doesn’t give the BTU/passenger-mile for light rail. Is it better or worse than heavy rail? And how about bicycles? What’s their BTU/passenger-mile? I bet they beat motorcycles.
Merged two threads on the same subject into one.
In Wikipedia it says city buses may get about 6 mpg (I thought it was less). If that is true then an occupied bus needs only about 3-4 passengers to be more efficient than the average oversized SUV with one passenger (I’m being generous with the SUV). Now for rush hour the bus travels empty in one direction, so let’s double that to 7 passengers as the break-even. That still seems quite far from your numbers so I can only conclude that buses are, on average, traveling empty too often - non-rush hour routes, lightly traveled routes, etc. That bus at 3 AM seriously hurts the efficiency of the rush-hour bus. From a public policy standpoint, it might make sense in the analysis to separate rush-hour from other times. Rush hour is about efficiently using the road network and cheaply moving a lot of people along limited routes. Off rush-hour is about providing mobility to the poor who have no other choice. If we focus on rush-hour as the energy efficiency target, I think the advantages of public transit are likely to be much higher. And that makes sense. People who own a car don’t ride the bus at 3 AM. If you want to look at car vs bus/train, rush-hour is the place that makes sense. And I think for that case - displacing rush-hour single occupancy cars, public transit will win out.
There are two kinds of bus transit- regular old bus lines, and bus rapid transit (BRT) which are more efficient- riders board much quicker because fares are collected at the station, and greenlight priority reduces idling at intersections. Also, diesel-electric buses are just coming online- think Grand Rapids has 6 out of a fleet of 60ish.
In 20 years, we’ll probably doing most of our urban travel in programmable pods, Masdar City style.
I’ve been more confused by this column than I have by any in a while. How can the BTU per passenger mile for a train be constant, regardless of how many passengers are in the car? The additional weight of each passenger is negligible - I’d think a train car with two people would be nearly twice as efficient as a car with one - that is, I’d think the train engine would burn only slightly more total BTUs scooting a car with two people as opposed to one. And if the train car had 40 people, I’d think it’d be hugely efficient.
So why the constant numbers for trains and buses? And why does a car get more efficient with more passengers if the others don’t (what’s average passenger load? The savings listed implies it’s at least 1.4 people, which seems high. 90% of cars have the driver, period).
Finally, the point Cecil couldn’t follow from Dano the question poser was the one I’m making - Dano believes mass transit might be inefficient now, but if each bus and train car had more passengers on average, they’d be more efficient.
I’m ashamed of you. You should know that Electric Vehicles have already gone way beyond the " golf cart" stage. And, are most probably the solution. Check the Tesla and my article on the subject posted on americasright.com.
It’s not actually a constant - Cecil is using figures which have a typical number of passengers per vehicle in them. For automobiles, the average load factor was 1.57 persons/vehicle. For buses, 9.1, for air 97.2, and for rail the values ranged from 21.7 to 34.2 depending upon the type of rail, with a lumped average of 26.3.
The sources Cecil has disagree with an assumption of 90% being single-occupant.
Packing factor is a major variable, true.
A $110,000 car is nothing more than a toy for the rich. The sedan from Telsa will have a $60,000 price tag. These are not cars that will be widely adopted. What can you get for around $20,000?
Cecil was looking at a computed average for each category. Instead of one average we could have been given a range depending upon loading capacity. But Cecil was trying to simplify to show where they tend to stand in relation to each other, not look at the outlier conditions (e.g. we have an efficient sedan with 6 people crammed in vs a commuter train with one passenger).
I also am curious where light rail fits.
Great Dave said:
Sounds like a railless light rail. Fewer load/unload points, less stopping en route, fee collection separate from boarding and unboarding. Just using existing roadways over new transport route (i.e. rail lines).
If I’m understanding correctly, a bus uses 9.14300 = 39130 BTU to go one mile, and a car uses 1.573500 = 5495 BTU. So, assuming ajackson’s Wikipedia-quoted figure of 6 mpg for a bus is correct, the average car gets 6*39130/5495 = 42.7 mpg?
I think I broke my math bone somewhere…
I don’t understand how Cecil did not take into account the effect of increased ridership of trains when saying transit vs. cars is a wash. The calculus may appear to come out that way precisely because transit systems are underutilized. People’s mistaken belief that it’s a wash and there’s no environmental reason to switch maintains a self-fulfilling prophesy.
As for rush-hour vs. later, whether we’re talking about a poor/not divide depends on the city. Some cities deal with citizens who use transit to get to work, easing congestion during rush hour and helping environmentally, but who otherwise own and use cars. Other cities (certainly New York, to some extent Boston, SF, and maybe others) have residents without cars or who only have cars for weekend trips. One should also not discount the value in human lives saved from accidents and drunk driving (the other important reason for 3am buses) via transit use.
(Note: I forgot that diesel has a smaller energy density than gasoline in my above post. So the calculations are off by 10%, maybe.)
OK. Thanks, Una. The 90% came from, you know, absolutely nothing.
Oh, you did know? OK.
hogarth, this source says you actually get more BTU from a gallon of diesel than from a gallon of gas (130,500 vs. 115,000). So that would mean Cecil’s ‘average’ car must get even more than 42.7 mpg.
I think you’ve got it a little reversed - the Btu per vehicle-mile given was 5,517. Assuming 115,000 Btu/gallon (LHV) (http://bioenergy.ornl.gov/papers/misc/energy_conv.html), we get:
115,000 Btu/gallon / 5,517 Btu/vehicle mile = 20.8 vehicle miles/gallon
Edited: I guess you didn’t have it reversed, the problem was the assumption of bus miles per gallon.
The buses in the study were said to have a Btu/vehicle-mile of 39,408. Assuming that 130,000 Btu/gallon mentioned, we get:
130,500 Btu/gallon / 39,408 Btu/vehicle-mile = 3.3 vehicle miles/gallon.
Edited: what’s 500 Btu between ladies and gentlemen?
I, too, am curious about light rail, living as I do in a sensible city (Portland) which has plenty of light rail.
The article assumes that MP-BTU will go up for cars but not for transit systems. Is this a valid assumption? Can’t we expect energy efficiency improvements to be about equal?
I don’t know if there are any big breakthroughs in electric subway motors in the pipeline. I suspect that it’s easier to improve the efficiency of a car or a bus. 3.3 mpg? That sounds really poor.
My city (Toronto) has a number of hybrid buses in use, but they haven’t worked very well so far: