I encounter with 2 problems: 1- Travelling with kids and pets can be trouble when you want to open car windows to get some fresh air. They always attracted by outside and want to bend from window, or stick their arms out of window.
2- When you stop your car(for example to have a picnic)but you want to leave your kid inside playing, and at the same time you want to have an eye contact with him/her you should keep open the sliding door. It is a huge problem because kid can crawl outside easily.