Think I might have found the smallest DDI... this thing is comical.
https://goo.gl/maps/YGAmpHEEogTvDSVD7
Wow that thing is strange! I feel like maybe that one has been shown on here before but the more I look the weirder it is:
-weird bridge shape (and huge square footage with the frontage roads under)
-interesting frontage road to south (more bridge $)
-lack of eastbound off-ramp left turn (I guess you're supposed to use that south frontage road to turn around?) try some combos on Google maps directions for a laugh
(surprising DDI was most logical layout if you don't even have one of the four left-turn movements)
-more lanes on bridge in each direction than the upstream signals. This is one of my biggest pet peeves on DDI - both ramp terminals have 2 lanes vs 2 lanes...so what good is that third lane doing you on the bridge?
I guess you could define "smallest" as number or lanes or tightness of geometry. There's a DDI in NC that has really tight curves, I'd be impressed if any were tighter:
https://goo.gl/maps/K1wUKEnPDkeKW1jj9