Auckland Transport's plans to divert more buses through Grafton is on a collision course with residents.

The Grafton Residents Association doesn't want its suburb further cut off from the Auckland Domain - something which is already occurring with increased bus traffic and the widening of Park Road.

Auckland Transport is proposing to divert all existing bus traffic from Khyber Pass Road onto Park Road.

Spokeswoman Jacqui Wilkinson said the congestion is already heavy with around 400 buses coming past Grafton Bridge and Park Road.

"And it can take - even during lunchtime - about 30 minutes to an hour to reach a short distance, which is less that a kilometre from Grafton Bridge all the way through to Park Road. So it's already a highly congested route for the buses."

She said the bridge has a 30 kilometre per hour speed limit, but there are times when the buses are speeding because they're trying to catch up lost time on the Park Road circuit.

"There's certainly an awful lot of bus drivers that break that speed limit, and with the frequency increasing it's going to be wall to wall buses."

"I'm not sure how cyclists are going to ride across the bridge."