Boy was I slow on the uptake. You would think after all the bridges and roads Ive put into my terrains this would have been obvious from the start. You can gang as many bridge segments as you want and then run a road or rail road track across the top to support convoys, trains and your tank. You need to determine what the road bed elevation is for the type of bridge you are using. Because you will have to adjust the road or track to that elevation relative to the bridge object.
This is great for the AI convoys and trains. As a practical bridge, at every bridge segment meeting, from your tank you will see into the body of the next bridge for a few moments. But, you can drive across it.
Here is what I cobbled together today to test it. For long bridges it's a good idea to make a bridge group of 2-6 segments to then keep laying down to speed up production time.