Associated Press

While nobody was seriously injured Tuesday and service was quickly restored, each accident raises questions about what will happen next to the century-old transit system.

"I think it's a classic problem that we have in the United States — the premier transit systems like New York and Chicago and Boston (have) serious deficiencies," said Robert Dunphy, a researcher at the Washington-based Urban Land Institute.

Unfortunately, he said, "it does seem to take a catastrophe to get people to focus on it."

That was certainly the case in Minnesota, where a bridge collapse in Minneapolis that killed 13 people caused armies of inspectors to fan out and take a close look at the state's other bridges. Illinois and other states followed suit.

The Minneapolis collapse is significant because a report released last month concluded that repairs to the bridge may have been put off for years, in part, because they were deemed too expensive.

"Financial considerations, we believe, did play a part in the decision-making" regarding the repairs, said Robert Stein, who oversaw the report prepared for lawmakers by the law firm Gray Plant Mooty.

In Chicago, officials make no secret that fixing the nation's second-largest transportation system will be tremendously expensive.

In January, when state lawmakers averted "doomsday" service cuts and fair increases with a bill that set up an annual funding stream of $500 million, officials said that amount would not be nearly enough for the kind of work needed.

Ten billion dollars over the next five years on bus and commuter train services was needed to "bring the system up to better repair, not necessarily good repair," Steven Schlickman, director of the Regional Transportation Authority, which oversees the city's mass transit network, said at the time.

Since then, even more trains have derailed, including one in April as it pulled into a station. A week earlier, an electrical problem caused a train to stall underground, forcing the evacuation of as many as 100 passengers.

Such incidents have Schlickman saying it may be time for a thorough examination of the system, RTA spokeswoman Diane Palmer.

After last week's derailment, Schlickman said he would "seriously consider" an audit, Palmer said. "And here we have another one (derailment) this morning," she said Tuesday, suggesting that an audit may be closer to happening.

As with the May 28 derailment involving elevated Green Line tracks, the CTA said a preliminary investigation revealed operator error caused Tuesday's accident on ground-level Red Line tracks. Spokeswoman Noelle Gaffney said the operator said he inadvertently passed a red signal, and when he realized his mistake, he stopped the train and then moved in the opposite direction, causing the train to derail.

She said there was no apparent damage to the tracks that might have contributed to the derailment.

Still, concerns linger.

"You have so much elevated track and a lot of it is very old," said Hani Mahmassani, a transportation professor at Northwestern University. "An accident could have disastrous proportions."

In fact, even as the CTA was saying that last week's derailment on tracks 22 feet above the ground was caused by operator error, it left open the possibility that the aging transit system played a role.

"The signals at this location were installed in the 1970s and refurbished in 1996," Gaffney said. "But some components are still more than 30 years old."

That is significant, Mahmassani said.

"It's operator error, but it involves signaling and signaling is part of the infrastructure," he said. "Modern systems tend to be more fault tolerant," meaning they are more apt to have backup systems that can prevent operator errors from becoming accidents.

Mahmassani applauded the CTA and emergency workers for their quick response to recent derailments. On the other hand, he said, the kind of problems with the CTA's inspection and maintenance program that the National Transportation Safety Board pointed to in a blistering report about a 2006 subway derailment "kind of explains what we're seeing."

"We are dealing with an aging infrastructure that has not been properly maintained," he said