In HK, there are no rules! You just hang on to the baby for dear life!
If it makes you feel better, use a Baby Bjorn to hold the baby to your chest (if they're young enough). Or, use one of those baby capsules that can be secured with a seatbelt.
The problem you will face is when they are bigger (like my toddler). We like to strap our toddler between us and the seatbelt.