New transport chief Mable Chan said on Saturday that further fee reductions at the Tai Lam Tunnel are not possible, as additional vehicle flow will lead to congestion during peak hours.

Writing on her blog, she said the bureau is actively improving transport facilities that connect to the tunnel, to ensure the takeover can be executed smoothly.

The government announced on Thursday it plans to charge time-varying tolls for the Tai Lam Tunnel after it takes control of the infrastructure in the New Territories on May 31 next year.

Instead of the present fixed toll of HK$58, private vehicles would pay HK$45 during peak hours, HK$30 during normal hours, and HK$18 during non-peak hours.

As for commercial vehicles – tolls are down from current level of between HK$64 and HK$79 to HK$43 throughout the day.

Chan said the time-varying tolls, in which vehicles will pay different fees according to “peak”, “normal” and “non-peak” hours, mean the fees for all vehicle types will be largely reduced, with “non-peak” hour fees set at the lowest possible price.

“Road pricing is an important transport management measure to regulate vehicular flow. Tai Lam Tunnel, including its control areas, is 10 kilometres long, which is the length of five Tsing Ma Bridges. The maintenance cost is not low,” she wrote.

“Tunnels are an important asset of the government. We have to abide by our strict fiscal discipline, and uphold the users pay principle,” she added.

Chan said the plans will help the tunnel reach its full capacity.