[asheshouse]

The solution was in this thread all the time --- on page 5

You need to set more Hot-Key options in conf.ini

I have used these entries

Shift NumPad-4=bridgeLeft
Shift NumPad-6=bridgeRight
Shift NumPad-8=bridgeOffset+
Shift NumPad-2=bridgeOffset-

bridgeLeft - rotates anticlockwise
bridgeRight - rotates clockwise
Offset moves the bridge along the axis of the route, but only up to half a pixel each way.

In addition Home and End rotates through the list of bridge options
Page Up/Down increases or reduces the number of spans

When you insert a bridge the left end is positioned on the nearest pixel centre so you need to make sure the cursor is over the correct grid intersect. Cant see any way to move the insertion point other than delete and re-insert.

Minimum bridge size is 3 pixels, 600m, comprising 200m of bridge with 200m of road each side. The bridge can be offset from the centre using the hotkeys listed above. The bridge must be located on ground at zero level otherwise the road sections on each side will be below ground.

I did try to simulate a tunnel by placing a long bridge and raising the ground in the central section to cover the bridge. Next time the file was opened in FMB the ground had been lowered automatically. Also tried running roads under rail bridges. FMB wont accept this either.

These Hot-Key commands are obviously vital. It would be a good idea to standardise the setup.
The Shift NumPad setup I have used may clash with existing setups that others are using.