Toting her violin case, Pittsburgh Symphony musician Linda Fischer was among the early birds at an open house yesterday on the Port Authority's plans to overhaul bus and rail service.

Among the 436 pages of proposed changes that the authority has posted on its Web site, Ms. Fischer found one that struck her as sour -- elimination of the 56E Greenfield route, which the agency says is "underutilized and provides very little unique service."

Riders of that route would be pushed to a reconfigured 56U Oakland-Greenfield line that goes to Oakland but not Downtown.

Many riders on lightly used routes face similar changes -- total elimination of their routes or consolidations that leave them farther away from the nearest stop or require them to transfer to get Downtown.

"I'm trying to encourage them not to do that," said Ms. Fischer, one of scores of transit riders who turned out for the all-day open house at the Omni William Penn Hotel, Downtown.

The authority is entertaining two "concepts" for service changes but intends to blend the best and most palatable of both into a final plan. Either way, there will be far fewer routes and stops.

By unofficial count, 51 routes would be eliminated altogether or merged with other service under both concepts. Another 28 routes would be abolished in one plan but not the other.

Detailed route-by-route descriptions of the proposed changes, including several planned new routes, are posted at http://tdp.portauthority.org/paac under the headings "Route Changes - Concept 1" and "Route Changes - Concept 2."

Another open house is set for 2 to 5 p.m. and 5:30 to 7:30 p.m. Monday at the University of Pittsburgh Alumni Hall, 4227 Fifth Ave., Oakland. Attendees can view a slide presentation, maps, and detailed descriptions of service changes, interrogate Port Authority staffers and register their comments on feedback slips or at computer terminals.

The authority will compile the comments, hone a final proposal in July and August and solicit more public input before putting the revised system to a board vote in September or October.

Generally, the changes are intended to better focus service where there is demand, not to cut service, said authority spokesman Jim Ritchie.

"Just because one route might disappear doesn't mean that in the end that area is going to lose service or that their service is not going to improve," he said.

Some riders might face a longer walk to the nearest stop in exchange for more frequent trips and faster travel times. Others will find themselves directed to park-n-ride lots.

Mr. Ritchie did not know yesterday how many of the system's 15,879 stops would be eliminated. On some routes, the proposed changes call for stops a quarter-mile apart -- a 15-minute walk at a moderate pace.

One of the concepts would consolidate Light Rail Transit to four renamed routes: a Blue Line from Castle Shannon to Downtown via Mt. Lebanon, Dormont and Beechview; a Green Line from Library to Downtown via Overbrook; a Red Line from South Hills Village to Downtown via Overbrook; and a Silver Line serving Allentown.

At least four little-used stops on the Blue Line, all in Beechview, would be eliminated: Traymore, Dawn, Pennant and Boustead.

The plan would abolish six little-used stops on the Green Line: Mine 3, Monroe, Lindermer, Hillcrest, Latimer and Center.

As part of a strategy to simplify service, most bus routes would see dramatic reductions in the number of variations. For instance, the 46G Elizabeth route, which currently has 36 variations, would have just two.

That means fewer buses meandering through neighborhoods to pick up a handful of passengers. It means that instead of walking to catch the 28E Robinson Express, Bill Jubeck of North Fayette will likely have to drive to a park-n-ride lot.

He said he started riding buses a year ago after a 40-year hiatus and has been pleased with the service "and, in particular, the courtesy of the drivers." But the authority's proposal wipes out a loop of the 28E that serves his neighborhood.

Mr. Jubeck said he fears the changes will be a hardship to those without automobiles, while others will drive past the park-n-ride lots and continue to Downtown in their cars.

But when asked if he might forgo transit, he said: "I've had a lot of experience sitting on Green Tree Hill and I don't want to duplicate that."