If I create the tunnel entry (given Ctrl), the tunnel section will no longer be created. :-[ (https://www.mediafire.com/convkey/3b2a/95v4ms6nrdyyllb6g.jpg)
This was a recent change, or did something break in the code? . ???
Could be this commit
There was problem that sometimes tunnel tiles were created, where they should not be: If build single tunnel portal on a lonely artificial slope with no hill behind. Afaict this commit brought back even older behavior to not create the extra tunnel tiles.
Unfortunately, a chapter breaks in the tutorial scenario, and I can not solve the problem. :-[
The problem is the ribi, in the entrances of tunnels can not be differentiated from a stretch of road.
For example, dead ends have ribi of: 1, 2, 4, and 8.
But in the entrances of tunnels they give a ribi of: 5 and 10.
Unfortunately this is no longer working when using the layered subway mode, since that little stretch of tunnel is now needed. :-[ look here: https://forum.simutrans.com/index.php/topic,20902.0.html
Tunnel portals can be very well differenciated from a road. It contains the tuneel object.
Also contruction in sliced and full underground mode worked for me in a recent nightly.