It's part of new laws aimed at tackling our relationship with drink.
The ban doesn't just cover public transport - there's now a 200 metre exclusion zone around schools, playgrounds and creches.
Children's clothing and cinemas are also covered, unless the film is over 18s.
Restrictions on how alcohol is displayed will come in next year - followed by a crackdown on how it's advertised at sporting events in 2021.
The HSE says the measures will benefit the health of thousands of people and families across the country.
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