Cant save vehicles with world editor (destructible bridges)

1. why when i try save what i made with the destructible bridge in east coast usa does it not save the vehicles but only what i deleted from the map. i put them in a sim group put can save and they dont spawn in, this is really anoying because i spent around an hour making the bridges seamless
   
   please help me i dont want to have to spend an hour placing bridges for 20 mins of fun.

 

You simply cannot for the moment.
There are some maps that managed to make this work, but there are only a few so I guess it's not that easy.

 

Even if im using the default ones? i dont understand it, how did the mod creator manage it?