terra cotta warrior

I see there is a bus service from the main railway station to the terra cotta warrior sites. Is there a similar service i can catch from Xian north as I will be travelling on the bullet train from Zhenghzou??. If not what is the easiest way to get from xian north to xian main railway station and how long does it take. What are the times of departure of the tourist buses from either site. thank you