In Newington, the road becomes New Britain Avenue and continues east through the Elm Hill neighborhood, briefly overlapping Route 173 near Churchill Park, then continuing east to end at an intersection with Route 176 (Main Street) after another 0.4 miles (0.64 km).

[1] A section of Route 174 in New Britain from its western terminus to East Street is designated the "Destroyer USS Braine Memorial Highway".

A section in Newington from the New Britain town line to Maple Hill Avenue is designated the "Master Police Officer Peter Lavery Memorial Highway".

Route 174 was established as part of the 1932 state highway renumbering and has no major changes since.

It was scheduled to be turned over to the towns in the 1962 Route Reclassification Act but the city of New Britain did not want to maintain the road and the state eventually decided to retain maintenance.