Three options for toll increases at the Cross-Harbour Tunnel have been proposed that could ease peak-hour congestion by up to 40 per cent.
The options were detailed in a government consultation document released yesterday.
All three would mean toll increases at the jammed Cross-Harbour Tunnel, from Hung Hom to Causeway Bay, and toll cuts at the Eastern Harbour Crossing, linking Quarry Bay and Cha Kwo Ling.
The three-month exercise is the second since a consultant's report was released in 2010.
Transport and Housing minister Professor Anthony Cheung Bing-leung said the measures could be in place in the second half of next year.
The government would compensate the eastern tunnel operator for loss of revenue, with the toll for cars falling HK$5.
This would involve multiplying the drop in fees by the number of trips made in the tunnel.
Tolls for the western tunnel will remain unchanged, because its connecting roads in Central are saturated, the bureau said.
Diverting traffic through it could be considered only when the Central-Wan Chai Bypass opens in 2017.
Under the first option, buses and trucks face the heftiest toll increase. Their tolls would rise by between HK$18 and HK$32, while cars would pay HK$25, an increase of HK$5.
This option is expected to divert 4,100 cars to the eastern tunnel during rush hour and cut the queue by 40 per cent. The bureau said many of the diverted vehicles would be trucks.
In the second option, private cars would pay a similar rise while other vehicles would be charged proportionally. This would mean the smallest reduction in traffic, cutting only 3,000 cars each day, or 30 per cent.
The third option exempts public transport vehicles from the increases, but car drivers would pay HK$10 more.
Queues would be cut by about 38 per cent, with 4,200 vehicles diverted to the eastern tunnel.
The difference between the revenue brought in by the extra tolls at the Hung Hom tunnel and the amount of money paid to the eastern tunnel in compensation for its loss would cost taxpayers HK$47 million a year in the third option and HK$11 million in the second option.
If the first option is adopted, the government would stand to gain HK$164 million.
Truck drivers said they would oppose any rise in their tolls.
A bureau spokesman said all three options would mean the diversion of a few buses, but said the government would be the "gatekeeper" on fares.
Kowloon Motor Bus said it could not comment before studying the options carefully.
New World First Bus and Citybus said they would study the impact on their costs.
The eastern tunnel operator said it was happy to discuss any options to ease traffic. Both tunnels are designed for use by 78,000 vehicles a day, but up to 120,000 use the Hung Hom tunnel and 70,000 use the eastern.