There are over 200 "secret" routes in Connecticut: highways with numbers above 400. "Secret" is just an unofficial term for unsignposted state roads and state service roads. Many of these are small auxiliary roads, or even long exit ramps.
The general public should never hear about secret routes, but they sometimes show up on maps, and a few road signs have even gone up.
This page discusses some of the more interesting routes in the 900s.
See also: selected 400's, selected 500's, selected 600's, selected 700's, selected 800's, or the complete list (400-999).