 The line is single track through very steep terrain rising 150 m above sea level in its 10 km length, with the highest point (152 m) at the north end of Kaka Tunnel.The ruling grade is 1 in 36, with long sections from Wellington to Crofton Downs and Khandallah of 1 in 40.There are seven narrow tunnels, six bridges, and three passing loops There are three level crossings with half-barriers; at the Simla Crescent and Khandallah stations, and at Fraser Avenue between Khandallah and Raroa stations (the Fraser Avenue crossing was last to get barriers as well as bells, in 2009).