State route 86 was the original number for the 8.5-mile north-south portion of Route 156 from Route 82 to US 1.
Route 86 was commissioned in 1932 from the old SH 150; in 1951, it become part of 156. This predates any plan of I-86, so while it looks like Route 86 was renumbered for the same reason as old routes 84, 91, and 95, this isn't the case.
From 1969 to 1983, Interstate 84 from East Hartford to the Mass. Pike was numbered I-86.
In late 1931, state planning maps had Route 86 marked instead as Route 155.