Thousands to ride over Harbour Bridge

More than 10,000 riders are expected to cross the Harbour Bridge on Sunday in the only chance they get to ride over one of Sydney's most famous icons.

Thousands of cyclists are set to ride across Sydney's Harbour Bridge for Spring Cycle on Sunday.

More than 10,000 cyclists are expected to take one of three courses, choosing between the 15km, 55km and 100km challenge.

Participants will take off at North Sydney about 6am, ride across the bridge, along the Cahill Expressway and continue through the Royal Botanic Gardens to the Rocks and Pyrmont.

The longer routes will finish at Sydney Olympic Park.

The event, organised by Bicycle NSW, aims at encouraging more urban cycling to reduce transport congestion and improve the livability of cities.

It's the the only time Sydney-siders can ride across the Harbour Bridge en masse.