This is a rendering of what a light-rail Purple Line train would look like running through the University of Maryland campus in College Park. (Maryland Transit Administration)

The leading bidder to build and operate a light-rail Purple Line in Maryland’s suburbs has proposed using rail cars from a Spanish company that made Metro cars being replaced 20 years early because they break down too often.

The same company has come under scrutiny in the past couple of years in Houston, Cincinnati and Kansas City, Mo., for delivering rail cars late and providing some that didn’t meet specifications. In Houston, for example, the company’s cars ended up 8,000 pounds heavier than the maximum weight sought, leading to higher electricity costs to operate the city’s light-rail system.

Purple Line Transit Partners, the team of private companies that two people with knowledge of the selection process say is the front-runner for Maryland’s 35-year Purple Line contract, has proposed using the company CAF to supply rail cars for the two-car trains.

The 16-mile Purple Line, now estimated to cost $2.16 billion to build, would link Montgomery and Prince George’s counties.

Metro’s 5000-series cars, which CAF supplied to the Washington Metropolitan Area Transit Authority in the early 2000s, have had a host of problems, including those that affect doors, the propulsion system and brakes.

Although the cars are relatively young, Metro determined that it would save $60 million by replacing all 192 of them rather than overhaul them at mid-life to keep them for an additional 20 years.

“The 5000 series has consistently been among the least reliable in the fleet,” Metro spokesman Dan Stessel said. “They require a great deal of ongoing maintenance.”

Among early problems with Metro’s CAF cars: A faulty circuit led to a woman being dragged along a station platform after her arm became caught in a door, and a fire broke out on a 5000-series car, the result of a heater that was not correctly wired. Initial problems discovered during the cars’ test phase led to a nine-month delay in Metro putting them into service.

Paul Shepard, a spokesman for the Maryland Transit Administration, declined to answer questions about CAF’s record with Metro or in other cities and would not confirm that CAF is a member of any Purple Line bid team.

“We are not going to respond to speculation,” Shepard said in an email.

Shepard also wouldn’t say whether the state is still on pace to announce a bid winner in February, as state officials have previously said.

MTA officials have declined to comment on any reported front-runner among the four teams competing for the Purple Line’s public-private partnership, which would be one of the largest government contracts awarded in Maryland. Under the partnership, a team of private companies would design and build the line over five years, help finance its construction, and then operate and maintain the line for 30 years.

However, the two people with knowledge of the process said the preferred bidder now in negotiations with the state is Purple Line Transit Partners, led by construction giant Fluor Enterprises Inc.

The team’s website doesn’t specify whether it would be CAF’s U.S. subsidiary, but the company recently has supplied other cities’ rail systems with cars assembled at a plant in Elmira, N.Y.

Two calls and an email to CAF’s U.S. headquarters in Washington were not returned Thursday.

A spokeswoman for Purple Line Transit Partners referred questions to the MTA but said the team’s website identifying CAF as a subcontractor was accurate.

Transit experts caution that rail cars are designed and built specifically for different systems, making it possible that some are lemons for one system while others from the same manufacturer work fine on another.

Although Metro was CAF’s first U.S. customer, it has had more recent problems in other U.S. cities.

In December, mechanics for Houston’s light-rail line found that wheels on some new CAF cars were separating from their axles.

The 39 new rail cars were delivered about a year behind schedule and ended up at 108,000 pounds each rather than the 100,000-pound weight ordered, Houston officials said.

Gilbert Garcia, chairman of Houston Metro’s board, said the agency will seek “remediation” from CAF to cover the $76,000 in additional electricity costs that the agency expects to incur annually from running the heavier trains over 30 or so years.

Even so, Garcia said top officials at CAF have been “very responsive.” He said CAF fixed the wheel problem and is investigating the cause.

“No doubt we’re disappointed in some of it, and we would have preferred no bugs,” Garcia said. “But with these projects, bugs sometimes arise, and the key is to deal with them quickly and effectively.”

Despite the delays and the wheel and weight problems, Garcia called the CAF rail cars “excellent.”

However, CAF has drawn repeated scrutiny for late deliveries of new cars.

In Cincinnati, the first streetcar ordered from CAF was due in mid-September and arrived Oct. 30, city spokesman Rocky Merz said.

He said the city’s contract specifies that CAF must pay $1,000 per day for late delivery of the first car and $500 per day for additional cars. Such penalties are “being tracked” as the city awaits the final two of its five CAF cars on order, he said.

He said the delays are not expected to delay the streetcar line’s opening, scheduled for September.

In Kansas City, Mo., CAF streetcars were several months late. Chris Hernandez, a spokesman for the city, said the delays won’t affect the city’s streetcar line opening this spring.

“I’d say we have a solid working relationship with them — we communicate with them constantly,” Hernandez said. “We worked with them to help them find ways to keep their production line going.”

The D.C. streetcar line, which is scheduled to open Feb. 27, does not include any CAF cars.