After US 6 leaves once again at exit 15 in Southbury, I-84 proceeds through hilly terrain into Middlebury, becoming more of an urban freeway as it enters the city of Waterbury, where it intersects the Route 8 expressway and crosses the Naugatuck River on an elevated dual-decked viaduct known locally as the Mixmaster.

I-84 turns more northerly for a stretch to exit 31 (Route 229), which provides access to Lake Compounce and ESPN World Headquarters.

In Farmington, US 6 joins I-84 once again at exit 38 and both meet the northern end of the Route 9 expressway at a half-used multilevel stack interchange that was originally planned to be part of the mostly-canceled I-291 Hartford Beltway.

A highway connecting Hartford and Providence was first brought up in 1944 as an upgrade to US 6 from Manchester to the Rhode Island state line.

[8] An environmental study by the Rhode Island Department of Transportation (RIDOT) was done in 1972; it was found the highway would cause heavy impact to Scituate Reservoir, the main drinking supply for Providence.

[9][10] After conducting multiple other studies, including briefly considering an alternate southern alignment that would bypass the Scituate Reservoir to the south and connected I-84 to the Route 37 Expressway, Rhode Island ended up canceling their segment of the highway in 1982, which ended up causing Connecticut to cut the segment to I-395 in Plainfield.

[16][17] Since the cancelation, other plans to have a freeway link between the two built segments have been proposed, including one in 2001, but was short lived, only lasting to 2003 before becoming dormant.

Similarly, the Wilbur Cross Highway (CT Route 15) merges with I-84 on the left side in East Hartford, and aligns with the lanes of I-84 heading northeast towards Sturbridge.

As designed, this would have allowed I-84 to continue east towards Rhode Island, and the Wilbur Cross Highway to follow I-86 to Massachusetts.

[25] Connecticut Attorney-General Richard Blumenthal has begun a lawsuit against the contractor and an engineering firm in response to threats from the US Department of Transportation (USDOT) to withhold funds from the project.

[30] In 2010, the Capitol Region Council of Governments (CRCOG), the City of Hartford, and CTDOT collaborated on a study of the corridor to begin the process of exploring reconstruction options.

That study looked at several concepts, including the rebuilding of the viaduct "in-kind", as well as several reconstruction alternatives that would alter the configuration of the highway.

The alternatives developed for that study were conceptual in nature—they did not look in depth at traffic, engineering feasibility, or environmental impact.

However, the strong stakeholder input as part of that effort was helpful in leading to CTDOT's decision to initiate the I-84 Hartford Project, to build on the good work of that earlier study.

Following full examination of the impacts and benefits of feasible alternatives, and, in collaboration with stakeholders and the public, CTDOT will make a final decision on how to reconstruct this section of the I-84 corridor.