Where in the US Constitution is the Federal government empowered to regulate the personal travel of Americans within the country? Where in the US Constitution

Where in the US Constitution is the Federal government empowered to regulate the personal travel of Americans within the country? Where in the US Constitution is the Federal government empowered to compel you to be subjected to dangerous radiation in order to board a common carrier? And why is this outrage limited to aircraft? I can step in a boat and travel down the local river past all sorts of critical facilities without screening. Every drug dealer in my town gets product from a wholesaler in NYC whose couriers use inter-city busses. You can drive around with legal explosive materials with the exception of some tunnels and bridges.