The Detroit People Mover. (AP Photo)

Advocates of the $64.6-million, 2.1-mile streetcar project often defend the transit line by pointing out Milwaukee is an anomaly among big cities without some type of rail system available to residents and visitors.

Moments after the Common Council approved the project in July, Mayor Tom Barrett said the streetcar would bring Milwaukee in line with other cities of similar stature.

Milwaukee, Barrett said, has to “make sure this city can compete with other municipalities, because we are the most densely populated city in the country that does not have a system like this. This is a significant step for Milwaukee.”

City officials, though, would do well to look closer at one of those aforementioned municipalities with a rail line.

The Detroit People Mover opened in 1987 to much fanfare, with a projected daily ridership of 67,700. An elevated 2.9-mile loop through Detroit’s downtown, the People Mover offers many parallels to Milwaukee’s planned streetcar project.

That should cause at least some concern, though, because the People Mover is a financial wreck operating under the prospect of shutdown. The system’s management board on Wednesday increased ridership fare by 50 percent. Even that increase might not be enough to keep the train moving into next year without cutting night and weekend service.

As it turns out, a 2.9-mile rail line covers relatively little ground in a major city. The People Mover, for instance, will carry passengers to stadiums where the Detroit Lions, Red Wings and Tigers play, but it won’t get them anywhere near other destinations, like the Detroit Institute of Arts, the Detroit Public Library or Wayne State University.

As one might expect, the People Mover is popular — and full — on game days, but a ghost train almost any time when there isn’t a major downtown event underway. The People Mover carried 6,071 passengers in 2010, or 61,629 fewer daily passengers than the city projected in the 1980s.

Detroit officials have floated plans to expand the People Mover so it would be more useful, but the Motor City has little capacity to pump $200 million into an already failing rail line.

Comparing the People Mover to Milwaukee’s planned streetcar, of course, is not apples-to-apples. Milwaukee has a more vibrant downtown with greater numbers of bars, restaurants, festivals and visitors.

But if the streetcar fails to expand beyond its initial 2.1-mile planned route, it could suffer from the same lack of route coverage as the People Mover.

Barrett says he has considered that possibility and is confident the streetcar would be a valuable resource even at a shade longer than 2 miles.

“Our preliminary designs for this were built on the assumption this would be all the money we had,” Barrett said. “Obviously, we’re going to do everything we can to get additional dollars from the federal government, because that’s the money that’s going to be spent on streetcars somewhere in this country.”

Even the initial streetcar route, city officials say, would drop off passengers within easy walking distance of 100 percent of downtown hotels, 90 percent of office and retail space and 77 percent of parking and housing.

Milwaukee also is starting out with much more conservative and reasonable ridership estimates. A study predicts 1,800 people would ride the initial streetcar route in 2015. The city also would charge $1 per ride, double the cost of riding Detroit’s People Mover.

As someone who lives downtown and enjoys — even prefers — rail travel, including the woebegone People Mover, I hope the streetcar project lives up to everything its proponents believe it can be.

But I also hope city officials keep an eye on Detroit.

The People Mover’s failure doesn’t necessarily forecast the future for Milwaukee’s streetcar. But it should give pause to great expectations.