National is promising to build Nelson's Southern Link highway if it wins the election, with work starting within three years.

Party transport spokesman Simon Bridges announced the plan in the city today.

"The investigation and design of the Nelson Southern Link was part of the programme in 2014 and today we're announcing we will get on and build it."

Bridges said, "the Nelson Southern Link will reduce congestion and improve travel times for people and freight moving around Nelson."

It will cost $135 million and include city connections and cycle and walking tracks.