Peak-season crowds at the city's busiest control point at Lo Wu could become the daily norm in a decade's time, analysis by the South China Morning Post reveals.
If Hong Kong receives the 100 million annual visitors by 2023 forecast last week by the government, then the checkpoint would be at 80 per cent of its capacity on an average day. The situation at the other railway control point at Lok Ma Chau could be even more serious, with average traffic above 90 per cent of its capacity.
While the Lo Wu checkpoint reaches 50 per cent capacity on an average day, the number of people handled there reached 85 per cent capacity on the busiest day of the first half of last year, government data shows. The Lok Ma Chau control point reached 91 per cent capacity on its most crowded day in the same period.
Mainland visitors have reported spending an hour queuing for manual checkpoints at Lo Wu on an average day, or triple that time on exceptionally busy holidays, such as National Day.
Control points at the airport, in Hung Hom and Shenzhen Bay exceeded their capacity on certain days last year.
Watch: Can Hong Kong's border checkpoints handle more tourists?
An immigration officer union said the rise in tourist numbers is already more than the Immigration Department can handle, while tourism insiders have urged the government to have better planning.
The Post's analysis assumes that each of the 45.7 million additional visitors enters and leaves the city once for every visit. That will increase the workload of each control point by a third. Last year, about 34 per cent of visitors crossed the border at Lo Wu and 16 per cent did so at Lok Ma Chau.
With 100 million visitors annually, that means Lo Wu control point will receive 85,640 travellers on top of the current average of 225,318 each day, while 41,568 more people will cross the border through Lok Ma Chau.
Dai Jian, from Hunan province, said it took him more than an hour to get through both Shenzhen's Luohu and Hong Kong's Lo Wu checkpoints - with most of that time spent waiting at Lo Wu.
"The queues move really slowly. It seems to me to be one of the worst-run checkpoints in the world," said Dai, a 38-year-old businessman.
Travel Industry Council executive director Joseph Tung Yao-chung said he feared increased strain on checkpoints could further negatively affect travellers' first impression of the city.
"Hong Kong has such a large [amount] of restricted land. Why can't more of it be used for expanding immigration facilities?" Tung said.
The Immigration Department claimed that 99 per cent of the visitors passing through Lo Wu, and 95 per cent at Lok Ma Chau, in 2012 were cleared in 30 minutes. But Ngai Sik-shui, chairman of the Immigration Service Officers Association, said this target could hardly be met during peak seasons.
Shenzhen resident He Yulin said problems exist even on off-peak weekends. He spends 30 minutes on the bus outside the Shau Tau Kok immigration building, then another half hour queuing inside. But the department said "all passengers were cleared within 30 minutes in 2012" there.
Ngai called the situation "very serious" as mainlanders not only complained to officers, some also started fights.
It is also getting harder to predict peak seasons. "We have seen crowds of tourists arriving for special events like the Brands and Products Expo in the past two years. The peak seasons are no longer limited to the two golden weeks," Ngai said.
In the Commerce and Economic Development Bureau's report on the city's capacity, it said the control points' capacity could be increased as more visitors use e-channels, and immigration procedures are further simplified.