confirm your distance; keep your distance
A fixed expression seen on road signage and in driving safety contexts, instructing drivers to maintain or check a safe following distance.
The sign on the expressway said 'confirm your distance'.
I learned the importance of keeping a safe distance at driving school.
車間距離 is the physical following distance itself, while 車間確認 is the act or instruction to check or maintain that distance.
Compound of 車間 (しゃかん, 'inter-vehicle') and 確認 (かくにん, 'confirmation'). A modern term used primarily in traffic safety contexts.