 The second change was the initial construction of Highway 406 in the mid @-@ 1960s , establishing a new northern terminus for Highway 58 at the St. Davids Road interchange on the Niagara Escarpment . The St. Davids Road interchange was fully opened with the Highway 406 extension to Beaverdams Road on November 21 , 1969 . Eventually Highway 406 would reroute the section of Highway 58 along the Merrittville Highway between Welland and Highway 20 to instead turn east from Niagara Street along Merritt Road , where it curved north to become the two @-@ laned Highway 406 . This happened when Highway 406 was extended south from Beaverdams Road to Merritt Road on June 30 , 1971 . 
