Maryland’s commuter trains are on schedule for about nine out of every 10 trips, a marked improvement from two years ago, when some trains ran late a third of the time and a string of high-profile delays culminated in a notorious breakdown dubbed the “hell train.”

Passengers say Maryland Area Regional Commuter (MARC) trains now stall less often, and when they do, conductors give more information, alerts go out more promptly, and backup trains and buses arrive more quickly.

Some longtime riders say MARC service had been deteriorating for several years before the June 2010 breakdown of a Penn Line train that stranded 1,200 passengers in sweltering heat for two hours without air conditioning. The highly publicized incident, which involved passengers calling 911 for medical help, appears to have prompted renewed attention to customer service and reliability.

“Trains seem to be relatively on time,” said Milton Mayo of Baltimore, who has ridden MARC’s Penn Line to his federal government job in the District for 20 years. “It’s an improvement from a few years ago, when on a fairly frequent basis there were delays and equipment failures.”

Krystal Quille, another Penn Line passenger, said she grew so fed up with MARC’s delays a couple of years ago that she moved to the District to avoid them. Since moving back to Owings Mills three months ago, she said, she has been pleasantly surprised.

“So far, it’s been the best [MARC] service I’ve had,” said Quille, an administrative assistant for the Justice Department, as she waited for a morning train recently. “It’s on time. There are no delays or [unscheduled] stops anymore.”

Most remarkable: Service has improved even as MARC has absorbed 9 percent ridership growth, or about 3,000 additional passenger trips daily, over the past two years. MARC carries a total of 35,200 trips daily.

Although many of those new riders are most likely trying to avoid rising gas prices, state officials attribute some of the growth to MARC’s improving reputation.

“They’ve certainly proved themselves in the last two years,” said Maryland Transportation Secretary Beverley Swaim-Staley. “It’s something we have to be vigilant about every day.”

Since January, MARC’s on-time performance is 96 percent on the Penn Line, 97 percent on the Camden Line and 92 percent on the Brunswick Line. In 2011, the on-time figures were 93 percent for the Penn Line, 90 percent for the Camden Line and 84 percent for the Brunswick Line. However, the 2011 figures include the summer months, when taxed locomotives break down more often and hot days result in track speed restrictions.

In 2010, all three lines hovered in the range of 82 to 89 percent for on-time performance, according to MARC figures.

“Compared to 11 / 2 years ago, it’s night and day,” said Rafi Guroian, chairman of MARC’s Riders Advisory Council. “The complaints we hear have returned to more isolated problems. They’re not the systemic failures we were hearing about two years ago.”

One problem that has grown worse with popularity: capacity constraints. More riders means more standing-room-only trains and station parking lots that can fill up by 7:45 a.m.

Passengers on the Brunswick and Camden lines still complain about delays from switch and signal problems and getting stuck behind freight trains. Brunswick Line passengers also complain that some of their coach cars are decades old and filthy.

Guroian said he wonders how much MARC’s recent on-time performance has hinged on the unusually mild winter, when tracks were spared snow and wet leaves. He said he is still concerned about how the older, problematic locomotives will handle a particularly hot summer.

Like many commuter rail systems, MARC continues to face another critical challenge: It doesn’t operate its trains or control the crowded tracks they’re on. The state pays Amtrak $50 million annually to operate the Penn Line between Washington and Perryville via Baltimore. It pays CSX $40 million annually to operate the Camden Line between Washington and Baltimore, and the Brunswick Line between Washington and points north and west, including Frederick and Martinsburg, W.Va.

Even so, Swaim-Staley said, MARC will continue to “tweak things,” as it did last spring when it added more frequent but shorter trains on the Penn Line to put less strain on locomotives. Another help: 26 new diesel locomotives recently came on line, she said.

Swaim-Staley said MARC passengers also should see some relief next year, when 54 new double-decker passenger cars are delivered, and in 2014, when a new MARC storage facility should reduce delays at Union Station.

Howard Carter Jr., Amtrak’s superintendent of commuter operations for MARC, said the shorter trains stay on schedule more often because they can accelerate and clear stations more quickly. Since the “hell train” breakdown, Amtrak also has stepped up customer service training for Penn Line conductors and paid more attention to patterns that surface in locomotive maintenance and inspections, he said.

“We looked at getting to the root causes of problems so we didn’t have repeat failures,” Carter said.