ZHUHAI (XINHUA) - The Hong Kong-Zhuhai-Macau Bridge, the world's longest cross-sea bridge, opened to public traffic at 9am on Wednesday (Oct 24).

The 55km bridge connects China's mainland province of Guangdong with the country's two special administrative regions, Hong Kong and Macau.

Starting on Wednesday, the customs in Zhuhai, Hong Kong and Macau will offer round-the-clock service for customs clearance to facilitate traffic via the bridge.

The bridge is the result of nine years of construction.

To ensure faster boundary crossings for passengers, the Macau and Zhuhai ports jointly use a one-off immigration clearance model, allowing travellers to queue up only once to finish both exit and entry procedures of the two cities in about 30 seconds, the China Daily reported.

Apart from private cars, taxis and cargo vehicles, two types of public transportation - shuttle bus and cross-boundary coach - can also run on the bridge.

Private cars will have limited access to the bridge, with special permits required to drive the entire distance.

Shuttle buses provide service only between the ports of Hong Kong and Zhuhai, and between Hong Kong and Macau, without crossing any boundaries. The frequency is about 5-10 minutes during peak hours.

Advance online ticket booking for the shuttle bus has been made available since 9am on Tuesday.

Most travellers will cross on shuttle bus lines. Large carparks have been built on either end for private cars.

A retiree from Zhuhai, surnamed Chen, told the South China Morning Post that she used to travel to Hong Kong by ferry, but will make use of the bridge in future.

"The fare is very consumer-friendly," said Ms Chen, who was in the business of building bridges before she retired. She added that the shuttle bus ticket had cost her 58 yuan (S$11.50).

Mr Jason Wong, 26, a tutor, said the trip from Kwun Tong to Macau was smooth, but he found the seat on the shuttle bus a bit narrow.

Since vehicles are driven on the right side of the road in mainland China and the left side in Hong Kong and Macau, the bridge includes a couple of points where drivers change sides.

With the bridge now open, the travelling time between Zhuhai and Hong Kong International Airport will be shortened from four hours to 45 minutes, and the time between Zhuhai and Hong Kong's container terminals will be cut from 3½ hours to 75 minutes.

Government estimates for traffic by the year 2030 have, however, been scaled back to 126,000 passengers daily, from about 172,000, New York Times reported.

The mainland city of Shenzhen, just north of Hong Kong, is building its own competitor bridge across the Pearl River that is expected to open in 2023.