half-hourly
/AmE ˈhæf ˌaʊ(ə)rli, BrE ˌhɑːfˈaʊəli 
/
A
adjective
there's a half-hourly service hay un tren ( or autobús etc. ) cada media hora
at half-hourly intervals cada media hora
B
adverb
cada media hora
half-hourly
English → Spanish
Oxford English–Spanish