A man walks into a bar with a roll of tarmac under his arm.

This classic bar joke hinges entirely on a delightful bit of wordplay, specifically a pun that takes a common idiom completely literally. The humor mechanism is the misdirection (Review) created by the setup, leading you to expect a typical bar scenario, only to be hit with a punchline that plays on the phrase "one for the road." While we usually understand "one for the road" to mean a final drink before departing, the joke cleverly interprets it as a literal drink for the *road itself*, personified by the roll of tarmac.

The idiom "one for the road" has been around for a long time, often used as a lighthearted way to suggest a last drink before leaving a social gathering. It's a culturally understood phrase that implies a final toast or a quick nightcap. The joke subverts this expectation by introducing the absurd image of a man carrying tarmac, transforming the figurative road into a tangible object that, in the context of the joke, also deserves a refreshing beverage. It’s the unexpected literal interpretation of a well-known saying, combined with the sheer silliness of the situation, that makes this joke a timeless chuckle.