Set up a custom question like this:
*Arrival Time[12:00][12:30][01:00][01:30][02:00][02:30][03:00][03:30][04:00][04:30]05:00][05:30][06:00][06:30][07:00][07:30][08:00][08:30][09:00][09:30][10:00][10:30][11:00][11:30]
Make it Type = 'Multiple Select'.