I had that happen. Thought it was a bug in SBX, turned out I wasn't paying close enough attention when selecting. The names are the same for roads and bridges, so I went in an made an edit in the SBX file to catch myself from choosing the wrong one. Here's the modified file, I just added BRDG to the descriptions for the bridges and haven't made the mistake since. File goes in the \SBX\Tools folder, backup the original.