Invisible Fence for Dogs: Keep Them Out of the Street

My sister just got the most adorable dog. She got a twelve week old Boxer. She has already had an Invisible Fence for Dogs installed so that once he is a bit older she can train him to stay in her yard. She wants to be sure he stays in the yard as her last dog was run over by a car when it got out of the yard. She wants to take every step possible to keep this dog safe. Her children were heartbroken last time when their dog got hit and my sister is going to take all steps necessary to be sure this dog doesn’t succumb to the same fate.