Basically it is pretty simple.
1. You have the map. Track 1, called MAP.
2. You create a separate layer with the road in red. Track 2, called ROAD You overlay track 1 with track 2.
3. You use a keyframed wipe or track matte to slowly show the layer 2.
It will be some work to get it right, but it can be done. The alternative is to get a dedicated plug-in for that.
I promise you that this is best done in After Effects using the pen tool to draw a path along the road. Everything you need comes standard in AE... no plugins.
^^^ This tutorial is so easy to follow, anyone can do it in just minutes. You can skip the arrowhead bit and just make the line follow the road, and it's even easier. I take this technique a step further and color the line/arrowhead with keystrokes so that I can animate arrows showing airflow through equipment that change color from red to blue and back to red, indicating the temperature of the air as it moves through the system.
After Effects can be an intimidating program, but give it a shot. You'll love the result.
Thank you very much for your prompt and very helpful answer. I now have a very smart looking road map, but most of all, it was really quite easy to create.
Thank you. I would like to try this, but not too sure how to get into After Effects.... I have seen comments on what a great program it is. Is it part of my Premiere Pro CS5 program, and if so, how do I open it?
After Effects is a separate program, available separately, or in the Production Suite or Master Collection.