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Is the El a waste of energy?
April 1, 2010

Dear Cecil:

In a recent Straight Dope column about whether mass transit wastes energy, you said "transit currently offers no energy advantage over cars except in the handful of cities with heavy rail — and not all of those. (Chicago's an outlier.)" Are you saying that, despite all those people crowding onto the trains, the El has no energy advantage over cars? How can that be?

— Gigi R., Lake View

Cecil replies:

Eh, maybe I overstated matters when I said the El was an outlier. But it's definitely at the far end of the scale. In fact, the El has the second-worst energy efficiency of major U.S. rapid transit systems. For anyone who's ever shouldered their way onto the Red Line, that may be hard to believe. How can packing ninety people into a box not be more efficient than one guy driving an SUV? Well, it is more efficient, but way less than you'd think. Who or what's to blame for that? Partly the laws of physics. However, a better target in my opinion is Evanston. Folks, not to put you on the spot. But for the sake of the planet, some sacrifices need to be made.

We'll get to that. First the big picture. Here's how the El compares to other U.S. rapid transit systems in terms of energy efficiency:

Energy Efficiency - Major U.S. Rapid Transit Systems

Agency BTUs Per Pass'r Mile, 2008
Atlanta (MARTA) 1,800
New York (NYCT) 2,000
San Francisco (BART) 2,400
New Jersey (PATH) 3,000
Washington, D.C. (WMATA) 3,400
Philadelphia (SEPTA) 3,700
Boston (MBTA) 4,100
Chicago (CTA) 4,200
Los Angeles (LACMTA) 4,400
Source: National Transit Database. BTU = British thermal units

The El, in short, uses twice as much energy per passenger mile as the rail systems in New York and Atlanta. To give you an idea what that means, energy consumption for a car with an average number of occupants is 3,500 BTUs/mile, according to the U.S. Dept. of Energy. As a practical matter, that means if you have at least one passenger, driving uses less energy — on average — than taking the El.

Why the poor showing? Some will say: because the CTA is run by bozos! Now, now. I spent some time with CTA management trying to figure what was up. Among the explanations offered: (1) in contrast to other cities, the El runs mostly above ground in a cold climate and costs more to heat; (2) the stations are close together, and speeding up and slowing down consumes energy; (3) the El uses old DC motor technology, not more efficient AC motors.

I'm sure all these things contribute. However, having done some noodling with the numbers, I'd say there's a simpler explanation — so simple it sounds almost ridiculous. 

It's the size of the CTA's rail cars. They're the smallest of any major transit agency. A fully-loaded El car holds about 90 people. A typical New York subway car can hold, on average, 243 — 170 percent more, although it's just 90 percent heavier. The more people you can pack onto a rail car, the greater the efficiency. Fact is, the CTA carries fewer riders per car each day than any other major agency in the country:

Ridership Per Route Mile and Rail Car, Major U.S. Rapid Transit Systems
Agency Weekday Riders Riders/
Route Mile
Daily Riders
per Rail Car
Los Angeles (LACMTA) 139,200 8,000 2,000
New York (NYCT) 7,791,000 34,000 1,500
Boston (MBTA) 481,300 12,700 1,500
Atlanta (MARTA) 247,200 5,200 1,300
Washington, D.C. (WMATA) 935,200 8,800 1,100
Philadelphia (SEPTA) 308,900 12,400 1,100
New Jersey (PATH) 244,300 17,700 900
San Francisco (BART) 358,500 3,400 700
Chicago (CTA) 646,300 6,000 600
Source: National Transit Database

Why doesn't the CTA buy bigger cars? It can't. Only small cars can negotiate the system's tight curves, especially in the Loop.

The CTA isn't completely stuck. It's buying new cars with longitudinal seating, which will boost capacity to 123 riders per car. The new cars will also have energy-saving AC motors. 

But my guess is these changes will produce only modest improvement. Additional increases in energy efficiency will have to come from better management — in particular, doing something about the parts of the El that are an energy sink. That brings us to the delicate subject of Evanston.

Here's a chart ranking the CTA's rail lines by a measure of efficiency called the Y Score. The score doesn't indicate energy efficiency, exactly. Rather, it measures how effectively a line makes use of basic rail resources — tracks and rolling stock. As you can see, El service shows considerable variation:

El Ridership Per Route Mile and Rail Car, By Line

Route Weekday Riders Riders/
Route Mile
Daily Riders/
Rail Car
Y Score
Red 228,900 10,500 840 88
Brown 93,200 8,200 690 56
Blue 142,400 5,300 540 29
Orange 49,000 3,800 610 23
Pink 27,600 2,500 770 19
Green 60,500 2,900 630 18
Purple 37,700 2,700 570 15
Yellow 4,800 1,000 800 8
Source: Ridership data from CTA Monthly Ridership Report – February 2010. Rail
car usage per line from CTA. Y score = riders/route mile Χ riders/rail car χ 100,000

Is the Y Score a well-known industry standard? Uh, no. I made it up myself. Y stands for "why are we doing this?" — a question, frankly, that needs to be asked. The high-scoring lines, the heart of the system, are an important urban asset. But others are pretty clearly are a waste.

Its amateur origins notwithstanding, the Y Score accords reasonably well with common sense. The Red Line scores highest, and the Brown Line does well too — both move a lot of people. The Blue and Orange lines trail distantly, which is perhaps surprising in the case of the former; the O'Hare branch is busy. However, the west side branch out to Forest Park is thinly traveled, and that pulls down the score. The lightly-used Pink and Green lines are a notch lower still, and one occasionally hears suggestions that one or both be closed. But that's never been politically palatable, and I'm not going there now.

Instead, let's talk about the Purple and Yellow lines. Setting aside city boardings on the Purple Line Express, ridership on these routes is pathetically low. More people board at Chicago Avenue on the Red Line (13,000) than at all Evanston and Skokie stations combined (12,000). Granted, running the Yellow Line takes only a handful of rail cars, so it's not a big drain on resources. But the Purple Line is due for major rehab. The CTA has enough trouble finding money to fix up the heavily used parts of the system. Why waste energy, literally and figuratively, on a marginal operation hardly anybody rides? 

The only local stops on the Purple Line with significant traffic are Davis Street and to a lesser extent Main Street — and they're both a short distance from Metra commuter stations. You can make an argument that the Purple Line ought to be eliminated altogether. If that's too radical, the simplest solution would be setting up a Howard-Main-Davis shuttle, and closing the other stops. 

Whatever happens in Evanston, it's hard to imagine any justification for continuing the Purple Line Express in its current form. These trains travel between Howard and Belmont half empty, then fill up from Belmont south. In other words, they're reasonably full for maybe five miles out of a 30-mile round trip. Also, let's face it, as expresses go this one is pretty useless — rocketing nonstop for the first half of the journey, then poking along behind Brown Line trains for the remainder. Surely a less wasteful approach would be longer Red Line trains, or better yet, a proper north side express service that would save energy and shorten travel times. (Yes, I have some ideas along these lines. Yes, I'm a rail geek. Sue me.)

No doubt cutting back on the Purple Line won't sit well with green-minded Evanstonians, who like transit in theory even if they don't use it in practice. But trains are only green if people ride them. If all they do is suck up resources, what's the point? 

(Click here for a followup column.)

— Cecil Adams
Photo by Pat O'Neil

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