Routes 50 and 54 have never existed.
CT 51

In the 1960s and 1970s, Route 51 was the number for the 9.2-mile section of present-day US 1, running inland from I-95, from Old Lyme to East Lyme.

This road was part of the original US 1 as well, dating from the 1920s. When the new expressway opened (circa 1950) between Old Lyme and East Lyme, US 1 was rerouted onto it, and the former US 1 went without a number. In 1958, the expressway became part of the Connecticut Turnpike, and soon afterward Interstate 95 as well.

In 1963, Route 51 was applied to the former US 1. But in 1977, US 1 was rerouted back to the inland route; the expressway became I-95 only; and Route 51 disappeared. Ashes to ashes, dust to dust.

 
CT 52

No longer assigned; renumbered in its entirety as I-395.

The Route 52 number was applied Sept. 15, 1964 to two sections of highway that had not previously been numbered: a segment of the Connecticut Turnpike from Waterford to the US 6 cutoff (SR 695), and a segment of "relocated Route 12" extending north to Route 101. "Relocated Route 12" was more of a planning number for the non-turnpike section, since there isn't evidence of it having been signed Route 12.

Route 52 becomes an Interstate

The idea of designating Route 52 as an interstate highway dates to the early 1970s. What spurred this idea forward in Connecticut, however, was Rhode Island's cancellation of its portion of I-84 in 1982. Connecticut decided to still extend I-84 anyway, to end at Route 52 in Killingly. If Route 52 were another interstate highway, state officials reasoned that getting federal approval and funding for I-84 would be easier.

In late 1982, Gov. William O'Neill asked the U.S. Transportation Secretary to consider an interstate designation, calling the route a "logical addition" as it links I-90 and I-95. Route 52 already met the physical standards of an interstate highway -- the other main criterion for acceptance.

For a while, it appeared Route 52 would become an extension of I-290 leading south from Massachusetts. A Hartford Courant article using the I-290 designation appeared just six days before the state announced on June 20, 1983, that Route 52 was promoted to I-395.

Route 52/I-395 plays a part in the aftermath of the cancelled I-84 to Providence, plans to address tourist and casino traffic, and even the southern terminus of the long-awaited Route 11. There's more information at the I-395 page.

More:

Route 52 lives, sort of... in mid-2000, a CT 52 sign was sold on eBay.

Sources:
  • "Highway Dept. Tacking Route Labels on Turnpike." Hartford Courant, Aug. 25, 1964.
  • "Interstate Status Urged for Route 52." Hartford Courant, Sep. 4, 1982.
  • "State Ordered To Lift Ban on Tandem Trucks." Hartford Courant, June 14, 1983.
  • Route Change Notice, ConnDOT, June 28, 1983.
 
CT 53

23.57 miles; from US 1 in Norwalk to I-84/US 6/US 7/US 202/CT 37/CT 39 in Danbury.

History:

Commissioned in 1932, Route 53 originally ran south from US 202 (now Route 302) along Redding Road (now Routes 53 and 107) to Georgetown, then south on Weston Road (now Route 57) to end at Route 57 in Weston. Route 53 was changed to its present configuration in 1963.

Jon Persky writes: "CT 53 roughly follows the path of the old Newtown Turnpike, famed for a spectacular pillage-filled march by British troops in April 1777. CT 53 and Newtown Turnpike are still one and the same from the northern split with CT 57 at Weston Road, to Redding near CT 107. The road still exists (although as Newtown Ave. in Norwalk) from CT 53 just north of its terminus at US1, all the way to CT 58 near the Redding/Bethel line."

All-American Road? No thanks

A 2.3-mile stretch of the Route 53, between Route 107 and the Weston town line, was nominated in September 1997 by the Housatonic Valley Tourism District for the All-American Road and National Scenic Byways Program, sponsored by the Federal Highway Administration. Locals attribute the road's beauty to strict land-use regulations and tracts of open space (portions owned by The Nature Conservancy and the Redding Land Trust, among others).

Two other Connecticut highways -- the Merritt Parkway and Route 169 -- are likewise honored. Some federal funding is available for maintaining such roads.

However, the Redding Planning Commission declined the nomination in October 1997, reasoning that national recognition would lead to increased traffic and road widening, eventually detracting from the town's rural charm. Said chairman Diane Taylor: "We do not desire to be recognized on a national scale."

More:

This road is ignored (no interchange) by Route 15.

Since US 1 is north-south nationwide but travels mainly east-west in Connecticut, residents are used to variations in directional signs for that road.

In Norwalk, however, a sign on US 1 northbound tells drivers to turn left for Route 53 east, as if the road to Danbury, about as straight north as it gets, was sucked into US 1's compass-spinning vortex.

Sources:
  • "Tourism agency nominates part of Route 53 for honor." News-Times [Danbury, Conn.], Sept. 23, 1997.
  • "Redding declines road designation." News-Times [Danbury, Conn.], Oct. 3, 1997.
  • Persky, Jon. "Re: NY-CT-MA-NY Roadtrip (1/20/02)." Post to misc.transport.road, Jan. 22, 2002.