The mainland section is a four-lane freeway with an interchange at the Thousand Islands Parkway in addition to its terminus at Highway 401. The section on Hill Island is a two-lane highway with limited development and two at-grade intersections, which will be twinned and likely converted to an interchange when the bridges are twinned. Connecting the two segments are the first bridge between the Ontario mainland and Hill Island, which is a toll bridge in the southbound direction. Northbound tolls are paid on the New York mainland. The highway ends at the U.S. Customs post, where it becomes I-81.
Until very recently, there were no Highway 137 signs posted; the designation was a hidden one that only existed internally due to the potential for motorist confusion. There was already a Highway 81 (which has since been decommissioned) in Ontario, so that designation was not available. Instead, the highway was signed only with the trailblazers "TO 401" northbound and "TO I-81" southbound. In 2006, Highway 137 signs were posted along the highway, although the trailblazer signs are still present as well.