[yt]http://www.youtube.com/watch?v=CLHUA1v9kiM[/yt]
[yt]http://www.youtube.com/watch?v=8e36gUTytjA[/yt]
Apparently they are cheaper and more durable then standard conrete and steel bridges...
[yt]http://www.youtube.com/watch?v=8e36gUTytjA[/yt]
Apparently they are cheaper and more durable then standard conrete and steel bridges...