Greenwich is crossed east-to-west by Interstate 78, which has interchanges with north-to-south Routes 143 and 737 in the township.
Main east-to-west roads include U.S. Route 222 (which interchanges with Interstate 78/Highway 309 in the extreme north,) Lower Macungie Road, and Mountain Road in the south.
Interstate 78 crosses Lower Saucon east-to-west with access from 412 at the Bethlehem/Hellertown line and Highway 33 in the northeast.
Signage for Exit 40 on Interstate 78, for example, refers to "The Plainfields" as a destination.
Interstate 78 and Route 61 interchange in the township just west of the river.
Interstate 78 crosses Upper Bern west-to-east with an interchange in the village of Shartlesville.
Upper Saucon has three north-to-south numbered routes: 309, 145, and 378. In Lanark, 309 comes north from Philadelphia via Quakertown to join Interstate 78 coming east from New York City and cross the mountain to Allentown.
Interstate 78 crosses east-to-west in the north and its Easton interchange is with Old Philadelphia Road/Morgan Hill Road in the township.
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Lehigh Street is one of several major Allentown-area exits off Interstate 78, which runs from the Holland Tunnel and New York City in the east to the Harrisburg, Pennsylvania area in the west.