Several lawmakers on Thursday said the government should lower tunnel tolls during non-peak hours, to cut congestion by encouraging drivers not to use the crossings during busy periods.

The government plans to raise tolls for private cars using the Cross-Harbour Tunnel and the Eastern Harbour Crossing, and lower fees at the Western Harbour Crossing, in order to help redistribute traffic.

But lawmakers said cutting the toll differences at the three tunnels won't tackle congestion problems, as the traffic flow during peak hours exceeds the total capacity of the tunnels.

Kowloon West lawmaker Scott Leung said residents in the district are worried that diverting traffic to the Western Harbour Crossing will make the situation worse.

"They are worried that traffic congestion would even be serious at the Western Harbour Crossing during peak hours. They could choose to pay more to avoid the traffic before, but they would lose this choice later," he said.

The lawmakers suggested a three-tier pricing system for private cars at the Western Harbour Crossing, with HK$60 charged between 7am and 10am and 5pm and 8pm, HK$30 between 10am and 5pm, and HK$15 between 8pm and 7am.

They added that a HK$15 overnight charge could be applied to all three cross-harbour tunnels.

Legislator Gary Zhang said lowering tolls during non-peak hours would encourage drivers to use the tunnels at different times.

"Because we suggest different charges for different time periods... we might be able to attract some flexible users to use the tunnels during non-peak hours because we are providing some economic incentive," he said.

Zhang added that the government should speed up plans to build a fourth cross‑harbour tunnel.