What Interstate and US Highway have you not been on for the longest time.

[Alex]

I try to revisit routes before too many years pass, but its been since September 2006 for I-82 and OR/WA in general. For 3di's was last on I-105 in Oregon in April 2005. Maine's 3dis are June 2005.
US Highway, likely US 201 in Maine from June 2005, edit US 199 in Oregon in April 2005.

The last section of Interstate I had not been on since childhood was I-90 between Buffalo and I-86 near Erie. Finally took that again last August; was on it previously in August 1989.
The last sgnificamt section of Interstate I did solely at night was I-84 between I-380 and Newburgh, NY in October 2004. I have at least some photos of every other Interstate otherwise and I only have 88 miles of I-81 and I-781 left to clinch...that's not including the AK and PR legislative ones.

[paulthemapguy]

I haven't been on the western I-76 since a family vacation to Colorado when I was 12.  This was in 2002.

[oscar]

The only time I've been on the Puerto Rico unsigned Interstates was over the Labor Day long weekend in 2002. I'm pretty sure I've been on part of every other Interstate (including Alaska's unsigned Interstates) since then.

US routes, I'm not sure.