Singapore has sought to open its borders to more forms of travel in recent months, but has also had to adjust the measures in response to the escalating Covid-19 situation. Here is a look at the measures:

1. Air travel bubbles

• Hong Kong: Singapore's first two-way air travel bubble. People will be able to travel between the two places without the need to be quarantined, subject to conditions including testing negative for Covid-19 more than once.

• Was to be launched in both directions on Sunday (Nov 22), but was postponed because of the rise in Covid-19 cases in Hong Kong.

2. Unilateral opening of borders

• Open to travellers from Brunei, New Zealand, Vietnam, Australia and China.

• Unilateral openings are a standing invitation from Singapore to these countries, which are deemed to have successfully controlled the spread of Covid-19.

• Allows for all forms of short-term travel, including leisure travel.

• Visitors have to take a swab test on arrival, and can go about their activities after they test negative. They have to use the TraceTogether app.

3. Bilateral green-lane arrangements

These allow for essential business or official travel between both countries. China was the first country to establish a green lane with Singapore.

• Japan: The Business Track allows for resumption of cross-border travel and business exchanges, with necessary public health safeguards such as testing before travellers leave and after they arrive, and adhering to a controlled itinerary for the first 14 days.

• China: A green lane is established with six provinces and municipalities: Shanghai, Tianjin, Chongqing, Guangdong, Jiangsu and Zhejiang.

• Malaysia: Singapore has two schemes with its neighbour. The Reciprocal Green Lane facilitates cross-border travel for essential business and official purposes. The Periodic Commuting Arrangement allows Singapore and Malaysia residents with long-term immigration passes for business and work purposes in the other country to periodically return home for short-term home leave.

• South Korea, Brunei, Indonesia and Germany: Conditions for travel similar to those with the other countries, such as pre-departure and post-arrival testing, and a controlled itinerary for the first 14 days.