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:

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