Route description
Route 10 begins at a diamond interchange with Interstate 95 (I-95) as Ella T. Grasso Boulevard in The Hill neighborhood in the city of New Haven, New Haven County. Ella T. Grasso Boulevard continues west as a four-lane undivided, municipally-maintained street to a T junction with Kimberly Avenue, just west of the I-95 interchange and east of the West River.
Route 10 then heads northwest through mixed areas of development, parallel to the river on the east. The route crosses over Metro-North Railroad's New Haven Line, which also carries Amtrak trains on the Northeast Corridor, before reaching a four-way intersection with U.S. Route 1 to the southwest of Evergreen Cemetery.
Past US 1, Route 10 enters the West River neighborhood, where it intersects Route 34, [2] which connects westwards with the Yale Bowl and eventually Derby. The route turns northeast, narrows to two lanes and comes into the residential Edgewood Park Historic District after crossing Chapel Street. A short distance later, Route 10 turns left (northwest) again on Whalley Avenue, which is city-maintained, to the east towards the Yale University campus, while Ella. T Grasso Boulevard (still municipally maintained) continues northeast into the Beaver Hills neighborhood. The route widens to four lanes until it reaches its intersection with the southern terminus of Route 63. Route 63 continues northwest and takes the Whalley Avenue name, while Route 10 turns northeast onto the undivided, two-lane Fitch Street. On Fitch Street, the route passes through more residential areas and the campus of Southern Connecticut State University, where it briefly divides into four lanes.
After leaving the university, Route 10 enters the town of Hamden before turning right (east) onto Arch Street, which continues west as a town-maintained street to Pine Rock Avenue. Shortly afterward, the route turns left and north-northeast onto Dixwell Avenue, which continues south back towards New Haven. Route 10 becomes a four-lane undivided road through a mix of residential and commercial areas, running to the west of Lake Whitney, before it crosses the Mill River and reaches another interchange with Route 15, the Wilbur Cross Parkway. From the parkway, the route parallels the river to the west, passes between several shopping centers, prior to briefly gaining a median to accommodate a gas station and passing under the right-of-way of the Farmington Canal, then reaching its four-way intersection with Whitney Avenue. Here, Route 10 turns north onto Whitney Avenue, which continues south towards New Haven, while Dixwell Avenue continues east to US 5 in the town of North Haven. The route passes through the center of Hamden, prior to intersecting the western end of the Route 40 freeway, which provides access to I-91; a flyover ramp exists from southbound Route 10 to eastbound Route 40. Past Route 40, Route 10 immediately intersects the western terminus of Route 22, which heads east towards North Haven, prior to passing near the campuses of Quinnipiac University and Sleeping Giant State Park in the Mount Carmel neighborhood. At this point, Route 10 reduces to two lanes and begins to parallel the Farmington Canal to the east, before it leaves Hamden and becomes the South Main Street of the town of Cheshire.
In Cheshire, the route passes residential areas, before reaching commercial areas near the center of town, intersecting the east end of Route 42, as well as passing east of Cheshire High School. At the center of Cheshire, Route 10 has a brief concurrency with Route 68/Route 70 to the west of the Cheshire Academy; Route 68 heads east towards the town of Wallingford and west towards the town of Prospect, while Route 70 leads east towards the city of Meriden and west towards the city of Waterbury, the latter via a connection with I-84. Past the triplex, the route's name changes to Highland Avenue and passes to the east of the Cheshire Correctional Institution, before it reaches an interchange with the I-691 freeway, which provides access to I-91 eastbound in Meriden, and I-84 westbound. Shorty past I-691, Route 10 passes to the west of a park-and-ride lot, prior to coming to an oblique junction with Route 322, with a bridge over that highway; access from northbound Route 10 to eastbound Route 322 and from westbound Route 322 to southbound Route 10 is via Old Turnpike Road. At this junction, the route comes into both the town of Southington and Hartford County as Cheshire Road, and shortly afterward becomes Norton Street in the Milldale neighborhood. Route 10 crosses the Quinnipiac River, and passes east of another park and ride lot, to the south of its intersection with connector ramps to and from the eastbound direction of the I-84 freeway, before becoming the southern leg of North Main Street of Southington.
The route heads into the center of the neighborhood of Plantsville, where it insects the western leg of North Main Street that provides full access to I-84, and it also turns northeast onto the mainline North Main Street. Route 10 turns north again at its northern intersection with Old Turnpike Road, before intersecting the northern terminus of Route 120, which provides access to Route 364 in Southington Center. The route also passes through the Southington Campus of the Branford Hall Career Institute, prior to becoming Queen Street at the Flanders Street intersection. From here, Route 10 heads through a commercial zone, expands to four lanes, and comes to a partial cloverleaf interchange with I-84, before it narrows back to two lanes after its intersection with West Queen Street. The route enters the town of Plainville as it intersects the southern terminus of Route 177, where its name also changes to East Street. In Plainville, Route 10 heads through a mix of residential and commercial areas, before it crosses the Highland Division of the former New York, New Haven, and Hartford Railroad at a grade crossing, and shortly afterward, Route 372 at an oblique intersection; eastbound Route 372 provides access to both the I-84 and the eastbound direction of the Route 72 freeway. Past Route 372, the route passes under Route 72 without an interchange, and continues through a residential neighborhood as Farmington Avenue. Route 10 heads back into areas of businesses as it leaves Plainville and becomes the Main Street of the town of Farmington. The route comes into wooded areas, prior to reaching another oblique, grade-separated junction with US 6, in which Scott Swamp Road provides the access not provided by the ramp from northbound Route 10 to eastbound US 6.
From US 6, Route 10 continues into the areas of historic Farmington Center, before intersecting and crossing Route 4, providing access to I-84 eastbound and the town of Unionville westbound. After the Route 4 intersection, the route begins to parallel the Farmington River on the west and its name changes to Waterville Road, as it passes through a country club and more wooded areas of residences. Around its intersection with Talcott Notch Road, Route 10 enters the town of Avon, continuing through large-lotted residential zones, before meeting its southern/eastern junction with US 44 in the village of Alsop Corner; US 44 continues eastbound towards the town of West Hartford. The northbound state route joins a duplexed concurrency with westbound US 44, along the Main Street of Avon that crosses the Farmington River, before reaching the northern/western junction with US 44 and the southern junction with US 202 in Avon Center; US 44/US 202 continues west along their own duplexed-concurrency toward the towns of Canton, where westbound US 202 splits, and Winsted. Meanwhile, northbound Route 10 turns north again and forms another duplexed concurrency with northbound US 202 along the Avon Veterans Memorial Highway, and heads through mix of residences and business parks, before becoming Hopmeadow Street upon coming into the town of Simsbury. In the village of Weatogue, the routes meets the west end of Route 185, which heads east towards the town of Bloomfield, and east of Simsbury Center, intersects the northern end of Route 167 that provides access to Route 309.
US 202/Route 10 continues through the historic residential and commercial areas of the center of Simsbury, before intersecting the western terminus of Route 315, which leads northeast toward the village of Tariffville. The two routes head into wooded residential zones and enter the town of Granby as Veteran's Highway, before becoming Salmon Brook Street. In the center of Granby, US 202/Route 10 are briefly triplexed with northbound Route 189, up to the Route 20 intersection, where northbound Route 189 becomes duplexed with westbound Route 20, and heads northwest towards the village of North Granby. The routes continue through more areas of forests and residences, with some businesses around, until Connecticut Route 10 ends at the Massachusetts state line and US 202 continues north, into the town of Southwick, Hampden County. A continuation of Connecticut Route 10, Massachusetts Route 10, begins at the state line duplexed with US 202, and crosses Massachusetts, which in turn continues into New Hampshire as New Hampshire Route 10, as part of the legacy of 1922-designated multi-state New England Route 10.
The Southington section of Route 10 was dedicated on Aug. 6, 1960 (and rededicated on Oct. 6, 2007) as the Louis G. Tolles Memorial Highway in honor of the late Southington native and leader of the Connecticut State Grange (1885–1956).
I-95 / SR 745 in New Haven 
US 1 in New Haven
I-691 in Cheshire 
I-84 in Southington 
US 6 in Farmington 
US 44 / US 202 in Avon 
US 202 / Route 10 at the Massachusetts state line
