The government has said that after March 2019 “your driving licence may no longer be valid by itself” in the EU, in its latest no-deal planning papers.
To be able to drive your vehicle in the EU an application may be needed to gain an international driving permit for UK citizens. This could impact on recreational drivers but would severely impede commercial drivers ability to carry out their jobs.
An international driving permit is required to drive in Japan, some US states and other countries outside of EU zone.
More to follow
https://www.thelondoneconomic.com/opinion/the-savage-brexit-letter-that-doesnt-pull-any-punches/26/07/