The Waterview Tunnel had a large, but only temporary, impact on Auckland's congestion problem, a new AA report shows.

After the multibillion-dollar road opened in July last year, commuters in the notoriously gridlocked city saw up to 11 minutes shaved off their rush-hour trips.

"Everybody noticed it. It got easier right across the network, both on the motorways and the arterial roads," AA spokesman Barney Irvine told The AM Show on Thursday morning.

"Eleven minutes were shaved off the trip in on the Southern Motorway, post-Waterview. That's a pretty big change."

Airport-CBD trips were seven minutes quicker, and commuters coming from Albany and Westgate via the Northern and Southern Motorways respectively saved five minutes each.