Hello! We will be in France, Zürich and Lucerne, and Venice. We will have a 2 1/2 year-old and a seven month old. Will we need to bring along car seats for taxis and trains and bus rides?
No. It’s not a legal requirement to have a car seat on public transport, and in any case US child seats are not legal in Europe. Chest straps are a legal requirement in the US but are not allowed in Europe.
It’s more complicated than you’d think. Here is a good article : https://travelcarseatmom.com/should-you-bring-your-car-seat-to-europe/
US car seats are not legal in Europe. Likewise, European car seat are not legal in the US. Obviously, many parents do travel with their own care seats and I’m not sure if there have ever been any prosecutions for doing so. Renting a car seat is rarely satisfactory as you’ll often get one that is not the right size for your child. It is quite a minefield for parents.