I've seen people strap the infant car seat into the bike trailers. I am not sure how they do it though. Basically, the rule that we followed when our DC were younger was that we allowed them to ride in the trailer when they were old enough and strong enough to wear a helmet on their heads comfortably. I believe that most kids helmets say that they are not intended for children under the age of 1, but we didn't follow that. We followed our own childrens' abilities. You could always go to the bike shop where they sell them locally and talk to a sales person there and check out all of the features yourself.