Simon: There are two ways to go to the airport. You can either drive over the ABC fly-over bridge or make a right at the XYZ corner.
Mary: What is a fly-over bridge?
Simon: It's a road built over a junction or crossroads. It has one end of it lying on one side of the junction, usually around 200 to 300 metres from it, slopes up as it nears the junction and falls slowly off onto the other side of the junction.

Can someone please tell me if the above conversation sounds natural?

Are the expressions drive over/fall off correctly used? Please suggest improvements, if any.