The road is the first of five new toll roads being introduced between now and the end of next year.
First motorists will be allowed drive over the new bridge over the Suir at Waterford after 4.30pm, following the lunchtime opening of the by-pass, which is 23km long and cost in excess of €500m.
The bridge is the longest cable-stayed such construction in the state.
Motorists using the independent tolling and parking system operated by Easytrip can use the by-pass with their existing electronic tags.
