The alternative access is from Saint Arnaud (). Just east of the township, the route turns right off State Highway 63 onto Rainbow Road (also known as Wairau-Hanmer Springs Hydro Road). This route follows the Wairau River to Island Saddle, which is New Zealand's highest legal road at . From there, it is to the turn off to Lake Tennyson. This road is suitable for four-wheel drives only, has seasonal access restrictions, and a toll applies that is payable at Rainbow Station.