The project concerns portions of I-81 — built in the 1950s and 1960s — that are deteriorating and in some sections do not meet current safety standards and are experiencing high accident rates. This is especially true of the 1.4-mile (2.25km) viaduct, near downtown Syracuse, NYSDOT said.

Two of the tunnel solutions run along Almond Street, one with a distance of about 2 miles, and the other of 1 mile. Both options would require cut-and-cover construction because of soil conditions and a high ground water table under Almond Street, as well as the need to treat and dispose of saline water, according to NYSDOT.

A third tunnel would be located under different street, but will still require cut and cover construction. The fourth solution would place I-81 in a new tunnel approximately one mile east of the existing highway, a minimum of 81ft below the surface where it could be bored through bedrock.

The costs of the different tunnel options range from USD 1.7 bn to 3.3bn.