Green’s Dictionary of Slang

tan track n.

[Rodgers, The Queen’s Vernacular (1972), suggests an origin in hobo use]

the anus.

X. Herbert letter cited in Simes Dict/ Aus. Und. Sl. 200/2: ‘He rides best on the tan track’, meaning he is asodomite, a bugger.
[US]Trimble 5000 Adult Sex Words and Phrases.
[US]B. Rodgers Queens’ Vernacular.
[US]S. King Christine 63: Inside I begged Arnie to tell this fat fuck to bore it and stroke it and drive it straight up his old tan track just as fast as it would go.
[US]S. King It (1987) 668: The first M-80 is going to go right up your old tan track, Vic.