Route 305 is one of the busiest surface roads in Windsor, serving office parks and connecting downtown Windsor to I-91 and Route 187. Long-term capacity improvement alternatives include widening it to a four-lane boulevard.
In the 1920s, State Highway 305 followed today's Route 315.
Route 305 started out as a highway the state did not want.
Today's Route 305 comprises Bloomfield Avenue in Windsor, and Old Windsor Road in Bloomfield (a mirroring found in many neighboring towns). In 1961, as the state highway reclassification was underway, the 2.45-mile Windsor portion was state-maintained, as unposted SR 905. The Bloomfield portion was a town road.
SR 905 was scheduled to be deleted from the state system, leaving the road completely under town maintenance. Instead, probably resulting from negotiations with the two towns, the state instead announced it would add the Bloomfield portion connecting to SR 905 to its highway system in late 1962. In 1963, the extended SR 905 became signed route 305.
Until guide signs were revised in the 1980s, the exit signs for Route 305 on I-91 read "Bloomfield Avenue / Windsor" with a Route 305 shield tacked onto the top border.
In early 2004, Bloomfield officials pursued a federal grant to study improving Route 305 and building a new connector road westward to Route 189. Construction, if deemed warranted, could take up to 20 years.
The 2-mile connector road would extend westward from the 187/305 intersection, crossing West Dudleytown Road and Peters Road, to end at Tunxis Avenue (Route 189). Planners believe it might relieve traffic congestion at Cottage Grove Road (Route 218) and Blue Hills Avenue Route 187.
In November 2007, the Capital Region Council of Governments (CRCOG) started a corridor study for all of Route 305, including the proposed extension. A longer Route 305 could help separate residential areas to the south from industrial areas to the north, and relieve traffic from nearby local streets. Several public hearings would "(h)elp identify a clear community vision as to how the road should look and function." The study was completed in 2009.
CRCOG also studied long-term capacity needs for the year 2030. Commuter traffic would require two westbound lanes in the morning, and two eastbound lanes in the afternoon. Four alternatives for widening were listed: