In 1948, Route 15 was assigned to those roads, as well as the Berlin Turnpike, Charter Oak Bridge, and Wilbur Cross Highway toward Union and Massachusetts. With the continuous Route 15 designation, a continuous exit numbering system was devised. The highest exit number ever in Connecticut, Exit 106, was for the Route 171 interchange on Route 15 in Union. Along with that, exits on the route were renumbered to be consecutive with existing number on I-84. The Route 171 interchange just ahead of the Massachusetts state line, once Exit 106, is now Exit 74.
Some expressways have exits without numbers.
Nineteen expressways do have exit numbers. Exit 2A and 2B westbound. Exit 61, Interstate 291, follows, with Exit 59 coming after. With interchange reconfigurations in the I-91 reconstruction near Route 20, southbound travelers now encounter exits 39 and 41 before exit 40. Most of I-95 is the former Connecticut Turnpike, whose exits were numbered from 2 in Greenwich to 90 in Killingly.