Q. Is it ever correct to use “roadtrip” versus “road trip”?
A. If you write roadtrip as one word because that’s simply what you prefer, then you can establish that as your style through repetition of the word. But unless you’re writing poetry or fiction, you’re probably better off choosing the form that readers will expect.
As a simple n-gram will show, two-word road trip is many times more common than one-word roadtrip in published books. Most dictionaries don’t even record roadtrip. Wiktionary, which had more than 1.3 million entries for English terms as of August 1, 2026, is an exception. (For that number, see Wiktionary’s “Statistics” page, under English. That doesn’t count the many terms from other languages that are defined in English-language Wiktionary, including the German Roadtrip, borrowed from English but spelled as one word and, because it’s a noun, capitalized.)
As for whether the one-word form is “correct” (in English, that is), there’s no law that dictates how compounds are formed; whether any two words remain open or closed depends on common usage and may change over time, as in the case of to day > to-day > today (see the entry for today at OED.com). But if you’re planning on road-tripping, you should probably pack some extra hyphens.
See also CMOS 7.89 (on the trend toward closed compounds) and 11.42 (on German capitalization).