Additional manpower will be deployed at the Cross-Harbour Tunnel as the city's electronic auto-toll system comes into effect there on Sunday, transport secretary Lam Sai-hung said.

Drivers will no longer have to stop and pay tolls when using the crossing from 5am.

Writing on his blog on Saturday, the minister said it is "extremely challenging" to introduce the HKeToll at the Cross-Harbour Tunnel, given that it is the busiest in Hong Kong.

An emergency transport co-ordination centre will come into operation in the next two days, and there will be more staff to handle any emergencies, he added.

Lam said the new tolling system is a prerequisite for introducing time-variant fees at all three harbour crossings later on, and that officials aren't simply relying on the HKeToll to ease rush-hour congestion at the tunnels.

The government is hoping to implement the new tolling system at the Eastern Harbour Crossing and Western Harbour Crossing next month, before introducing it at Tate's Cairn Tunnel and Aberdeen Tunnel later this year.

Lam added that once the HKeToll is set up at Aberdeen Tunnel, officials will tear down the toll plazas and build bus interchanges there.