Mask effect is not rendering

If everything looks right in preview but when you render it doesn't, I wonder if it's as simple as accidentally sending the wrong element to the render queue.  Your video footage and comp are named the same thing and it's a simple mistake to click on the file in the project panel and send that instead.

Go to Composition > Composition settings and rename your comp.  That should solve the first guess. Next, if you can post a screen recording of the preview and your final video, that might help spot what's going on.

Last guess for now - i noticed the thumbnail in the project panel for the comp is showing an empty road.  Is it possible you used Composition > Save Frame As or Rendered an image sequence instead of a video?  With the composition selected (highlighted in blue) go to File > Export > Add to Adobe Media Encoder.  AME will open as a separate program, from the first dropdown select H.264

I'll second that we will need more information here. 
Can you post the export itself? The original clips? A screen recording of what you're doing here?
The more context you give us, the more help we can offer!

Well, perhaps you simply need to set your work area and render start time accordingly, as apparently all you magic starts way in. Either way, you may want to read the online help on some basics:

After Effects User Guide

Anything more will require specific info like what the actual render settings are.

Mylenium