Route 29 is a state highway in the U.S. state of New Jersey . It runs 34 @.@ 76 mi ( 55 @.@ 94 km ) from an interchange with Interstate 295 ( I @-@ 295 ) in Hamilton Township in Mercer County , where it continues as I @-@ 195 , to Route 12 ( Bridge Street / Race Street ) in Frenchtown , Hunterdon County . Between the southern terminus and I @-@ 95 , the route is a mix of freeway and four @-@ lane divided highway that runs along the Delaware River through Trenton . This section includes a truck @-@ restricted tunnel that was built along the river near historic houses and Riverview Cemetery . North of I @-@ 95 , Route 29 turns into a scenic and mostly two @-@ lane highway . North of the South Trenton Tunnel , it is designated the Delaware River Scenic Byway , a New Jersey Scenic Byway and National Scenic Byway , that follows the Delaware River in mostly rural sections of Mercer County and Hunterdon County . The obsolete Delaware & Raritan Canal usually stands between the river and the highway . Most sections of this portion of Route 29 are completely shaded due to the tree canopy . Route 29 also has a spur , Route 129 , which connects Route 29 to U.S. Route 1 ( US 1 ) in Trenton .