These are .mct files created using these base objects.
Gold bridge is Hoops object
Steel bridge is Sand2 object
Wood bridge is Mailbox object
I have added the .png files too for your own use in creating your own .mct files
If you want to know how to create and install your own mods/ .mct files/ .png files then maybe take a look at these forum posts.
How to install .mct files - https://www.ape-apps.com/viewpage.php?p=16002
How to create mods and .mct files - https://www.ape-apps.com/viewpage.php?p=15943