There are many, many intersections of supplemental roads throughout Missouri. The intersection of Routes RA and J in Callaway County is notable because Route RA consists of only a few hundred feet of road into the Little Dixie Lake Conservation Area near Millersburg.
The R series of supplemental highways (usually RA but there's an occasional RB, RC, or even RD in a few counties) is used for spurs into state parks and conservation areas.