These icons () show footnotes as tooltips... for some browsers.
Apologies to those of you looking for Intel chip information; while the i486 preceded the Pentium, I-486 is an old numbering for a freeway in western New York.
Further apologies to those looking for information on the abortion pill; there's no RU-486 information here, either.
Unfortunately, each time I mention anything this page doesn't cover, the search engines consider it more relevant.
I-386 (unknown history) New York (link)
Allegany County, Department Of Public Works Committee Meeting, June 6, 2001. The minutes include the following:
A motion was made by Mr. Reynolds and seconded by Mr. Bennett to make a Resolution accepting funds from the State of New York for a feasibility study of a proposed Interstate 386.The motion carried, with "Resolution to be approved by county attorney." There's no other citation on the web for this.
I-486 (numbered as another interstate) New York (link)
In 1971, Interstate 486 was the proposed numbering for today's I-390 , which was approved that same year for inclusion into the Interstate Highway System.  Construction began a few years later.
The 486 number is shown on a planning map in the document "Estimated cost of Completing the Interstate Highway System of New York -1971 edition," which Stephen Summers has scanned and hosted at his I-486 NY page.
A little about New York's I-86
Interstate 86 in New York is the new numbering for the Southern Tier Expressway (NY 17), which took place in late 1999. As the I-486 plan implies, New York had been advocating the I-86 numbering for decades before this. In fact, a nationwide planning map from 1956 includes a state request for an interstate highway (no number shown) in the Southern Tier back then.
If New York's wish had come to fruition around 1982, the United States at the time would have had three concurrent distinct Interstate 86 routes: one in Idaho (still existing), one in Connecticut and Massachusetts (now part of I-84), and one in New York.