Transport minister Lam Sai-hung on Saturday said the government is hoping for a 10 percent decrease in traffic once its new toll regime for the three harbour tunnels comes into force.

The Western Harbour Crossing will transfer to public ownership in August when its franchise ends, meaning all the tunnels will be government owned. Earlier this week, the government said it would stagger tolls for most vehicles depending on the time of day

Speaking on a radio programme, the minister said the change would result in some drivers using the tunnels during non-peak hours.

"Some people have flexible working hours. We are providing an incentive for them to change their travel habits," Lam said.

"We don't expect all people to avoid using tunnels during rush-hours. But we hope, after setting up different tolls for different time periods, the traffic will reduce by 10 percent."

Meanwhile by the end of the year, tolls for commercial vehicles - including minibuses - will be set at HK$50 for all the three tunnels at all times.

Minibus operators earlier said that fare hikes were likely as the new Cross-Harbour Tunnel toll will be five times the current amount of HK$10.

But Lam said the increase was reasonable.

"The average existing tolls for the three tunnels for public light buses is around HK$46. We now set a toll level for the public light buses at HK$50, so we consider that the toll level for commercial vehicles, including the public light buses, is appropriate," he said.

Lam added that the toll for minibuses for the Cross-Harbour Tunnel had not been raised in more than 30 years.