THERE’S commuter chaos on Sydney Harbour Bridge after a man climbed a pylon on the iconic structure during peak hour traffic.

The man reportedly climbed the bridge around 5.10pm today before lanes were closed.

A spokesperson for NSW Police told news.com.au the man was now in custody and undergoing a mental health assessment.

The incident has caused heavy traffic in the area but all lanes have since now reopened.

Thank you to the latest random climber of the Sydney Harbour Bridge. Cahill Expressway closed. Great timing #sydneytraffic #yourekiddingme pic.twitter.com/cUb6C7cTdh — JK (@Mr_Big_Bird) November 21, 2016