Green’s Dictionary of Slang

dirt road n.

also dirt run, old dirt road

the anus.

[US]H.N. Cary Sl. of Venery IV (t/s) n.p.: (human body) The Anus [...] dirt road.
[US]Monteleone Criminal Sl. (rev. edn).
[US]Trimble 5000 Adult Sex Words and Phrases.
[US](con. 1930s–40s) B. Rodgers Queens’ Vernacular 108: Hobo slang (kwn ’30s & ’40s) The ass itself became the dirt run, old dirt road and old rip. These words seem to indicate that pederasty was more important than fellation among the homosexual hoboes.
[US](con. 1962) J. Ellroy Enchanters 30: [of a divorcing wife] She’ll get wise and brown him up the dirt road.

In phrases

go up the (old) dirt road (v.) (also go down the dirt road, ...up the dirt route) [fig. use of colloq. dirt road, the highway]

to perform anal intercourse.

[US] ‘Adventures of a Fuller Brush Man: “The Amorous Mrs. Twirp”’ [comic strip] in B. Adelman Tijuana Bibles (1997) 47: ‘Up the Dirt Route’ Very popular with wolves, Greeks and other perverts.
[US]D. Maurer ‘Prostitutes and Criminal Argots’ in Lang. Und. (1981) 116/2: To go up the dirt road. To practice pederasty.
[US]G. Legman ‘Lang. of Homosexuality’ Appendix VII in Henry Sex Variants.
[US]Guild Dict. Homosexual Terms 12: dirt road, to go up the (old) (v.): To pedicate.
[US]R.A. Wilson Playboy’s Book of Forbidden Words.
[US]R.O. Scott Gay Sl. Dict. 🌐 anal intercourse: [...] Syn: goin’ down the dirt road.
[US]B. Keane ‘Dysfunctional Family Circus’ 🌐 I told you before we came up here, if Dad has too much to drink and wants to go ‘Up the Old Dirt Road’, it isn’t because he has to take a piss!
Sexionary at www.sarahhedley.co.uk 🌐 Go up the old dirt road – anal sex.
take it up the dirt road (v.)

to be sodomized.

Movie Films Fest ‘Legacy’ Rev. on Excalibur Films 🌐 Wide, hard cocks aren’t a problem for either of these anal sluts as both of them take it up the dirt road with slutty glee.