Car Seat for Babies 1 Year And Beyond

Hi, going to be FTM here. Just bought a travel system. However, understand that the infant car seat that can attach to stroller can only be used up till max maybe 1.5 years. I currently do not own a car but will depend on grab/taxi rides or use my father's car sometimes. Was wondering how to travel on cars once my baby outgrow the infant car seat as I notice the car seat for older babies or toddlers are not really portable. Any Mummies able to advise?