Darrell Sapp, Post-Gazette Port Authority workers bang power lines with poles on T line in Beechview, along Broadway Avenue. Click photo for larger image.

Port Authority officials are calling it an ice storm unlike any other -- with rain freezing to the overhead lines that power the Light Rail Transit system as quickly as passing crews could knock it off.

"I've been here since 1999 and we've not had this kind of ice storm," said Port Authority operations manager Steve Banta. "Five, six hours of steady freezing rain is not a normal occurrence."

Normal or not, the collapse of a rail system that managed to run when buses, airplanes and trucks could not in the spectacular blizzard of 1993 took many by surprise. Buses from the South Hills filled to standing room only when riders who ordinarily relied on the T found themselves traveling on rubber tires when steel rails failed.

The problem was the overhead power lines known as catenary wires. Those wires send current through lines attached to armatures -- called pantagraphs -- that rise out of the rail cars and catch current for their electric motors.

When rain began freezing onto the catenary wires, it formed a thick coating that blocked the current. The Port Authority sent out cars equipped with special pantagraphs equipped with serrated power wires -- cutters -- to shear off the ice and get the juice flowing again.

"Every time you chipped the ice, it froze again," Mr. Banta said.

Complications piled atop one another between 7 p.m. Tuesday, when the first Port Authority car equipped with one of the cutters became stalled against the frozen line and Wednesday morning. Two Port Authority diesel rail vehicles were sent to clear the overhead lines and to haul away trains as they stopped beneath frozen power lines.

The diesels, Mr. Banta said, "are pieces of equipment that are designed for short durations of work. They were actually under power and running for a very long time." Then one of the diesels broke down.

Yesterday, a breakdown on the Beechview line held up three cars in the 42S service originating at South Hills Village.

It was 8:10 a.m. before the disabled car was cleared and regular service resumed.

The Overbrook line was operating inbound only throughout the day and evening as ice-covered wires continued to plague the system. Outbound cars were sent out the Beechview-Dormont-Mt. Lebanon mainline.

The Library line remained shut down through the day and shuttle buses were used to bring commuters to Washington Junction and Castle Shannon where they could transfer to the light rail system.

Officials could not say last night whether full service would resume on the Overbrook and/or Library lines today.

"Nobody's more disappointed than I am," Mr. Banta said. "But it was an act of nature that we just weren't prepared for."

That plea found sympathy in the ears of at least one other transit official in the wintry Northeast. Joe Pesaturo, spokesman for the Metropolitan Boston Transit Authority, which runs long stretches of above-ground rail, said he couldn't imagine what to do with the storm that hit the Pittsburgh region.

"How do you prepare for six straight hours of freezing rain? What page in your preparedness manual do you turn to for that sort of thing?" Mr. Pesaturo asked.

In Boston, where rain does occasionally freeze, the MBTA policy is to run trains around the clock to keep the power lines clear. On Wednesday, ice temporarily halted rail service near Boston University when a train's pantagraph caught on a buildup of ice on a power line.

Other transit systems in regions where snow, ice and overhead lines interconnect have assorted ways of dealing with it. Some say they rarely lose service in ice storms.

"We generally have not had a problem operating. It's just the opposite. A lot of times, that's the only thing that's working," said Doug Hartmayer, a spokesman for the Niagara Frontier Transportation Authority, which runs trains in the Buffalo-Niagara region.

Niagara Frontier developed a system in which it assembles a four-car train, with the front train unpowered, and its carbon pantagraph wire jacked up to push against the line. Generally, said Mr. Hartmayer, that does the trick, and shears away the ice.

But the Buffalo system enjoys a special advantage. Beyond its rail yards, which are outdoors, it has only 1.2 miles of above-ground lines. Running the cars constantly to clear that area is far easier than the 25 miles of line the Port Authority must maintain.

In Toronto, where Canadian cold batters the overhead trolley power lines, the rare ice storms -- that far north rain usually freezes into snow before it can reach the ground -- don't often shut down the streetcars, said Dan Nicholson of the Toronto Transit Commission.

In serious freezes, Toronto puts the cutting devices on its streetcars, but neither Toronto nor Buffalo is especially fond of the devices.

"They have the potential of doing a little more damage," Mr. Nicholson said. The decision to install the devices came after December 2004. "We had a really bad ice storm," he said. "A lot of our streetcars ground to a halt."