Translation guide
In Japanese, the concept of a 'designated driver' is commonly expressed with specific terms, but the practice and phrasing differ from English-speaking cultures. The most natural equivalent is ハンドルキーパー, though other expressions exist depending on context.
designated driver
Most common term. Use this when referring to a friend who stays sober to drive.
The most common meaning: someone who stays sober at a social event to drive others home safely.
ハンドルキーパー is a person in your group who doesn't drink. 運転代行 is a paid service where a professional driver takes you and your car home. Don't confuse them.
A loanword from English 'handle keeper', widely understood in Japan. Refers specifically to the person who refrains from drinking to drive.
I'm the designated driver tonight.
Let's decide on a designated driver before going out drinking.
Refers to a paid service where a professional driver drives your car home. Not a person in your group, but a common alternative to having a designated driver.
I drank too much, so I'll call a driving service.
Literally 'person who doesn't drink'. Can be used to describe the designated driver in a casual, descriptive way, but not a set term.
Is there anyone who isn't drinking?
If we don't have a designated driver, let's use a driving service.
The literal translation 指定運転手 (していうんてんしゅ) is not natural Japanese. Stick with ハンドルキーパー.