Carterton is easily accessed by various transport modes:
Leave Wellington on SH2 following the signs for Masterton, and head up over the Rimutuka hill to Featherston. Continue north through Greytown and a further 10 mins north you will arrive in Carterton.
Google maps route from Wellington Airport to Carterton
From the north by road:
From Woodville SH2 leads directly south through Pahiatua, Eketahuna and Masterton. Take the bypass road around Masterton to reduce traffic delays; the road rejoins SH2 south of Masterton from where Carterton is a 10 minute drive.
Route from Auckland International Airport to Carterton
Catch the Wairarapa line from Wellington Railway Station, via the Hutt Valley and through the Rimutaka Hill tunnel to Wairarapa. Shortly after passing through the tunnel, look to your right for a superb view of Lake Wairarapa. The train stops at Featherston, Woodside (Greytown) , Matarawa, and then you arrive at Carterton’s historic railway station. The whole journey from Wellington takes an hour and a quarter.
Timetable is located here: The Trans Metro line map
It is possible to fly into Masterton Airport and from there arrange for transport to the Carterton district. There is a scheduled Air New Zealand flight from Auckland to Masterton.