It was supposed to hug both sides of the Delaware River between Trenton and Philadelphia, stretching 50 miles for bicyclists, joggers, and walkers to enjoy.

But 18 years after the Delaware River Heritage Trail was laid out on paper, much of it remains incomplete on the ground, and its planners are switching gears to make it all come together.

In the process, 10 more miles are being added to the map. The revised trail also will stray farther from the banks of the river than when it was initially planned in 1998. It will lead people into historic downtowns, through parks and tunnels, and through woods and the margins of rolling farmland.

"When we first started talking about the trail, we didn't anticipate meandering from the Delaware River," said Mary Pat Robbie, director of Burlington County's Resource Conservation Department, which is creating part of the trail on the New Jersey side.

Behind the project are the Delaware Valley Regional Planning Commission, local governments, and nonprofits such as the Delaware River Greenway Partnership.

As currently visualized, the trail will loop through 24 towns in New Jersey and Pennsylvania, linked by the Calhoun Street Bridge in Trenton in the north, and by the Tacony-Palmyra Bridge in the south, though some planners propose extending it to the Ben Franklin Bridge, which has a walkway.

Burlington County recently decided to add a detour so that trail users can avoid traveling alongside the heavily congested Route 130 in the northern end of the county. "This was the easiest way to get it done, basically," Robbie said.

This year, the county received a total of $3.1 million in federal grants to extend the Heritage Trail into Crystal Lake Park in rural Mansfield Township. Known as the Route 130 Bypass, the five-mile segment will take bicyclists and walkers from the Bordentown area, across the highway at a newly installed traffic light, and into the heart of the 370-acre park.

There, trail users will cross over Crystal Lake using a foot bridge and then travel past meadows, woods, and steep ravines.

"The park will be an attraction," said Matt Johnson, county coordinator of park development.

From there, the Heritage Trail will involve sidewalks and bike lanes to be built alongside country roads in nearby villages and will link to a trail that opened this summer along the old Kinkora rail line.

Trail users will then be directed back toward the Delaware, passing through a pedestrian tunnel the state recently built beneath Route 130 near the highway's Roebling exit, Johnson said.

Previously, the Heritage Trail planners had considered creating a bike lane alongside Route 130 but then discovered they would have to gain access to a cemetery and several commercial and industrial properties that line the truck-laden highway.

"The Route 130 segment was always going to be difficult, so we tried to come up with an enjoyable solution that's safer," Johnson said.

The funding for the Route 130 Bypass comes mostly from the federal Transportation Alternatives Program.

It will be used to connect segments of the trail that end in Roebling, one of the historic and cultural sites along the route. The village is the site of the now-demolished Roebling Steel Mill, which manufactured the cables used to build the Golden Gate and Brooklyn Bridges. The Roebling Museum is located at the site.

The Heritage Trail will then "sweep around and follow the Delaware River," Johnson said.

The newest segment also will connect with a part of the trail the country created three years ago. That 2.3-mile segment already runs through Bordentown City and Fieldsboro and links with a path that leads into Trenton.

On the Pennsylvania side, the route mostly follows the D&L Canal towpath but has a few interruptions that need to be addressed.

The segment that goes through Bordentown City takes in the historic downtown and the home of Thomas Paine, who famously wrote Common Sense.

The Bordentown stretch also contains a half-mile detour that takes bicyclists and pedestrians to the Bordentown City Beach, a gravel area alongside the Crosswicks Creek that is parallel to the Delaware River.

Work on the Route 130 Bypass is expected to start by next summer, Johnson said. If there are no major setbacks, he said, that part of the trail could be finished by the end of next year.