Taxi drivers are only charged HK$25 when using any of the three crossings.

“The current scheme is running smoothly at the three tunnels. But it has not resulted in significant reductions in traffic,” Law told a television programme.

According to the commissioner, the hourly number of vehicles travelling through the Cross-Harbour Tunnel during peak periods reached between 2,800 and 2,900, up from 2,600 before the new tolls took effect.

The total volume of traffic had also risen from 105,000 to 107,000 each day, she added.

“But we have noticed that more taxis are using the Western Harbour Tunnel, regardless of whether its peak hours or at night,” she said. “And we also observed that unlike before, more taxis are willing to make the crossing during peak hours.”

Transport Department data showed that the number of taxis using the Western Harbour Tunnel on August 2 – the first day of the tolls revamp – rose by 20 per cent during the morning peak between 7am and 10am and by 40 per cent for the whole day.

The commissioner also said the policy had contributed to smoother traffic at the busy Cross-Harbour Tunnel, pushing back the start of the 15-minute window for morning rush hour from 8.15am to 8.45am.

Hong Kong Automobile Association president Ringo Lee Yiu-pui said the increase in the number of vehicles using the Cross-Harbour Tunnel was the result of the new electronic toll system, or HKeToll, installed on July 23, allowing drivers to pay without stopping or queuing up, and the “still big” price gap between that crossing and the other two.

“The e-toll system allows more cars to pass through the tunnel in one hour. Meanwhile, the Western tunnel costs HK$30 more than the Cross-Harbour Tunnel. Who will be willing to pay HK$30 more every day? Drivers will just choose the cheaper one,” he told the Post.

But Lee agreed with Law that the “6-3-3” scheme did help to divert more taxis to the Western tunnel.

Law said the current measures were purely “transitional” and coming plans to vary tolls at each tunnel based on the time of day would “greatly reduce traffic congestion”.

She said authorities were confident the second phase would help divert traffic away from busier crossings and promote public transport, citing a government survey that showed a HK$20 toll difference could change the habits of motorists.

The poll collected responses from about 90,000 Hongkongers, 12 per cent of whom were private car owners, between September and January.

“They have provided us with a consistent answer that they would consider changing their driving habits if there was a HK$20 price difference at tunnels, including driving through seldom-used tunnels or even turning to public transport,” she said.

“But that can only be achieved after the second phrase is launched.”

The scheme’s next stage will see private cars travelling during peak periods at 7.30am to 10.15am and 4.30pm to 7pm charged HK$60 at the Western Harbour Tunnel, while fees for the Cross-Harbour Tunnel and Eastern Harbour Tunnel will be HK$40.

All three tunnels will charge private cars HK$30 between 10.15am and 4.30pm and HK$20 between 7pm and 7.30am the next day.

To deter drivers from rushing to cross before prices change, tolls will rise or fall by HK$2 every two minutes during the change over to peak-hour or non-peak-hour periods until they reach the maximum rate.

Commercial vehicles will be charged HK$50 at all three crossings. All three crossings will charge private cars HK$25 during the day and HK$20 at night on Sundays and public holidays.

But Lee expressed scepticism about the second phrase of the tolls revamp, questioning whether the price differences would encourage drivers to avoid using tunnels at peak hours.

“I am not here to challenge her confidence. But most private car owners in the city are not company directors. They cannot choose what time they start or finish work,” he said.

Lee suggested the government review the second phrase a month after its launch to see if further adjustments were needed.

“I believe that the most effective way to divert traffic is to apply the same toll charge to three tunnels,” he added.

Sunday also marked the first day of operations of the new HKeToll system at the Western tunnel.

Law said in a Facebook post that the system had operated smoothly and thanked people for the support given to her department.

“From the initial scepticism of drivers towards the e-toll, to now being generally accustomed to and anticipating its implementation in more tunnels for faster passage, I know that our efforts have not been in vain,” she wrote.

The system will be extended to the Eastern tunnel on August 27, and Tate’s Cairn Tunnel and Aberdeen Tunnel by the end of this year.

The e-tolls system already covers the Cross-Harbour Tunnel, Lion Rock Tunnel, Shing Mun Tunnel and Tsing Sha Control Area.

The system requires road users to apply for a tag, which is scanned for tolls, open a special account online and create a payment method. Vehicles no longer need to stop or slow down to pay tolls at booths at tunnel entrances.