Monday-Saturday,  there is

  a

Determiner

  half-hourly

  service

Noun

  to

Adposition

  and

Coordinating conjunction

  southbound

Adverb

  and

Coordinating conjunction

  to

Adposition

  northbound

Noun

.

Monday-Saturday, there is a half-hourly service to and southbound and to northbound.

Monday-Saturday, there is a half-hourly service to and southbound and to northbound.