I'm not on my regular computer so I can't double check to make sure this is what's going on, but I do think I know what you'll need to do. What you'll probably have to do is use the cookie cutter tool, layer both clips over each other and then open up the cookie cutter tool on the top clip. On this first layer (or track), make a square (using the cookie cutter tool) over the side of the road that the other clip (the second track) will fill in. Make sure that it's deleting all the inside of the square, and not the outside. Leave the second track alone. I'm pretty sure that should do the trick. Sorry if I'm off but I'm not on my home computer. Once I get home though I'll double check and make a better guide.