Tier 1 Bridge Spacings

Under the PBS Section in the toolbar, there is a Tier 1 Bridge Spacing button. This shows extra dimensions between axles that show the required minimum spacing. By default it assumes the mass to be GML limits as a worst case, however if you want to use your current gross mass you can click the drop down and switch it.
When a spacing is below the minimum required, the dimension will be highlighted red.
If the dimensions become overwhelming, they can be turned off individually in the Right Bar Dimension Panel under the Vehicle.