In recent years, summer has been a season of discontent for riders on Maryland's MARC commuter trains, as hot weather contributed to frequent engine breakdowns, track problems and power malfunctions that led to cascading delays.

The misery on the rails reached its deepest point during the infamous "hell train" incident in which a Penn Line train was stranded on the tracks in sweltering heat for two hours in June 2010.

But this year, MARC made significant gains in summer's on-time performance — especially on the Amtrak-operated Penn Line, Maryland Transit Administration records show. The improvement on that line, which accounts for roughly two-thirds of MARC's 34,000 riders a day, meant that thousands more commuters made it to work or home on schedule.

On the Penn Line, which runs between Washington and Perryville via Baltimore, on-time performance reached 94 percent in the May-September period, compared with 88 percent last year and 87 percent in 2009. Each warm-weather month in 2011 showed an improvement over the previous two years.

With that improvement, MARC commuters such as Eric Luebehusen of Jacksonville, who drives each day to Halethorpe to catch the Penn Line, had more evenings when he got home in time for family activities.

"It was a much better performance this summer than last," said Luebehusen, a tough MARC critic in previous years.

For each day with a single percentage-point increase in on-time performance on the Penn Line, about 210 more Marylanders get home or to work on time. That means that in June, when the improvement was an eye-opening 12 percentage points, roughly 2,500 more commuters made it home on time each day than on any given June day in 2010. With 22 working days this June, that translates into a lot of Little League games for which a parent made the opening pitch.

Luebehusen said he encountered problems and communications lapses, but no systemic breakdowns like the hell train.

"All in all, if I had to grade them, I'd have to give them a B — maybe be nice and give them a B-plus," he said. In previous years, he said, he would have been hard-pressed to give MARC a C.

Rafi Guroian, chairman for the MARC Riders Advisory Committee, said passengers have noticed the improvements this year.

Those steps apparently include the introduction of a new Penn Line schedule, revamped Amtrak procedures and the O'Malley administration's acquisition of 26 new diesel locomotives — a 2008 purchase whose full impact wasn't felt until this year.

The change was less remarkable on the smaller, CSX-operated Camden and Brunswick lines. On the Camden, which runs between Baltimore and Washington, the performance was significantly better than in 2010 but not as good as in 2009.

On the Brunswick Line, which connects Washington with Western Maryland and West Virginia, on-time performance dropped to as low as 78 percent in July and hovered in the low to mid-80 percent range the rest of the summer. The MTA said the Brunswick Line was severely affected by weather-related problems such as heat-related speed restrictions on the tracks and flash-flood warnings.

For MARC, the big question going into this summer was performance on the Penn Line. Early this year, MARC and Amtrak introduced a new approach to operating the line, running trains more frequently but with fewer cars to reduce the strain on locomotives and the power system.

Simon Taylor, the MTA's chief administrative officer, said there has been a noticeable improvement in the working relationship with Amtrak since the "hell train" incident, which exposed wide gaps in communication between MARC and the operator of its busiest line.

After being left aboard the rail cars for almost two hours with no water or air conditioning, angry passengers finally called emergency rescue workers to get them off the train. Members of the O'Malley administration from the governor on down spent weeks making apologies. Amtrak accepted the bulk of the blame and promised better treatment of MARC riders.

Taylor said that over the winter, the MTA and Amtrak worked out a new Penn Line schedule that was implemented early this year.

"The big thing has been working in partnership with Amtrak," Taylor said. Another factor in the Penn Line improvement, he said, was Amtrak's installation of a new electrical substation just outside Washington's Union Station, where many of the locomotive failures had been occurring.

Guroian agreed that Amtrak has been more responsive to MARC's concerns over the past year.