Hong Kong's new electronic auto-toll system was off to a smooth start at the Shing Mun Tunnels, where it launched on Sunday at 5am.

Under the HKeToll system, drivers no longer need to stop at toll gates to pay tunnel fees.

While the transition has been mostly successful, some drivers still slowed down near disused toll booths and required guidance from tunnel staff.

In preparation for the launch, special traffic arrangements were implemented, and the tunnel was temporarily closed at midnight to allow workers to close the toll booths and install signs that read "HKeToll Tolling. No Stopping".

The Commissioner for Transport, Rosanna Law, inspected the tunnel early on Sunday as the switch was made.

The Tsing Sha Highway first adopted the system earlier this month, and Lion's Rock Tunnel will follow next Sunday at 5am. The government plans to expand the system to all its tunnels in the territory by the end of the year.

More than 85 percent of the city's cars have already registered for the system.