Ardern said one was intended to be completed two years ago but had stalled and the cycle trails were important for jobs and tourism in the region.
Ardern said Labour would also set up an export engineering hub and invest $1 million to work with engineering businesses to add value to West Coast exports.
"Labour's plan demonstrates our commitment to the West Coast where the Labour Party itself was started in 1908 and our commitment to thriving regions around New Zealand."
Ardern's announcement followed a visit to Tai Poutini polytechnic where she watched a virtual reality project and met mechanic students.
She was also persuaded into getting into a raft by outdoor education students and being tossed around in a mock white water rafting trip.
There was some initial reluctance - possibly because the students were dressed in the colours of political parties and there were echoes of National's 2014 campaign ad featuring Labour and its potential coalition partners in a boat rowing in different directions.
To the audience at the Regent Theatre, Ardern also reiterated her pledge for a manned re-entry of the Pike River mine by the end of 2018, saying Labour would set up an agency to oversee that and take back the authority to conduct it. National has claimed the promise of a re-entry is a reckless political stunt which ignores its expert advice on the dangers of re-entry.
National is working on an unmanned re-entry.
