The New Zealand Transport Agency (NZTA) classifies the most part of State Highway 1 as a national strategic road. The exceptions are between Kawakawa and Whangārei and south of Mosgiel, where the SH 1 is classified as a regional strategic road, and north of Kawakawa where SH 1 is classified as a primary collector road. The sections between Wellsford and Wairakei, between Ohau and Wellington Airport, and between Woodend and Rolleston are classified as high volume roads. The section from the Central Motorway Junction and the Newmarket Viaduct, to the south, is the country's busiest section of road, with more than 200,000 vehicle movements a day between Khyber Pass Road and Gillies Ave.