Some express buses running between Hong Kong and Macau came to a halt as the two regions started banning non-residents from visiting.
Macau yesterday started requiring Hongkongers to go through a 14-day medical observation upon entry, while Hong Kong has also implemented mandatory home quarantine measures of the same length for those returning from Macau.
Two operators - Hong Kong-Macao Express and One Bus - suspended their services starting yesterday, while the Hong Kong-Zhuhai-Macao Bridge Golden Bus shuttle will continue to run hourly.
HZM Bus chairman Zhang Guangyou said passenger numbers dropped 95 percent since the measures came into force, with less than 100 yesterday morning.
He said the firm will adjust service frequencies based on passenger volume, but will not suspend them altogether.
Franchised bus services to the HZMB control point run by Kwoon Chung Bus - routes B4 and B6 - will also maintain hourly services.
Meanwhile, some foreigners arrived just before the SAR shut its doors to non-residents for 14 days from midnight yesterday.
One of the last flights, Emirates flight EK380 from Dubai, landed at 11.32pm on Tuesday.
A British passenger, Sally, came for a business trip and said she was lucky to arrive before the measures came into effect.
"I'm a Brit and in England, it's really bad . . . I actually think we're safer here because the [SAR] government seems to have managed it much better," she said.
Separately, a 33-year-old Hong Kong man tried to traffick drugs to Macau before the deadline but was arrested and more than 51 grams of cocaine, five grams of marijuana and 7,000 Macanese patacas were seized.