Union Boulevard runs beneath a third limited-access road between East Islip and Great River, Heckscher State Parkway. No access to this parkway is provided, however Exit 45W on the parkway leads to Harwood Road, which takes commuters to both NY 27A and CR 50. From the parkway bridge, the road enters both county and state protected areas. CR 50 then intersects with Connetquot Avenue south of Great River's train station. The road finally terminates at an at-grade interchange with NY 27A and the entrance to the Bayard Cutting Arboretum.
