If there's one thing for which Pittsburghers should all be grateful to Mayor Murphy, it is the system of bike trails around the city.

It has taken 12 years and $7 million, and it's still missing some key links, but Pittsburgh has gone from a paltry 2.5 miles in 1993 to its current total of 18 miles of completed trail and another 7.6 miles, including some of those troublesome links, in progress. The popularity of these trails among cyclists, scooter-riders, walkers, joggers and bladers of all ages is manifest on any sunny Saturday.

As the years have passed, the mayor has enlisted the aid of organizations like Friends of the Riverfront, the Riverlife Task Force and Bike Pittsburgh and augmented thin city funds with money from foundations, nonprofits and the state and federal governments to advance his dream of a spurred city loop ultimately connecting to the Great Allegheny Passage.

Much has been accomplished, and the trails inch farther afield and closer to connections every year, but Mr. Murphy is still struggling, as his term winds down, to blast through some persistent obstacles. Aside from the obvious challenges of Pittsburgh topography, trail advocates continue to battle problems with flooding, active rail lines and access to private property, through either purchase or negotiation.

The Panther Hollow railroad crossing and link to Schenley Park, the conduit across the Hot Metal Bridge, a safe path from the Smithfield Street Bridge to the Point and the elusive Next Great Park greenway along Route 51 have been stumbling blocks for years, and Sandcastle remains a stubborn barrier on the Steel Valley Trail to McKeesport and the corridor to Washington, D.C.

Pittsburgh's likely next mayor, Bob O'Connor, has not expressed a commitment to the trail system. But it is an asset to the city: an attraction to potential residents and a boon to current ones. The dashes won't be connected without sustained pressure, organization, clout and money. Fortunately, the recently passed federal transportation bill includes millions for our region that can be drawn on for trail improvements. Pittsburghers simply have to make it clear we want to finish the job.