Structure conflict
Work in progress: This section is still a work in progress — content is being added and revised continuously.
What is checked? Whether the bridges and tunnel portals you chose fit together. Trackplanner reports six cases: a portal standing on a bridge (the track is up in the air there); a portal whose mountain reaches under a bridge (the bridge wins there, the mountain is missing); a bridge in the middle of a tunnel; two opposite portals standing too close for a tunnel to form between them; a bridge so close behind a portal that the tunnel in front of it becomes too short; and a portal behind which no tunnel forms for another reason. For each portal it reports only the reason, not also “portal without a tunnel”.
Why does it matter? Bridges and portals shape the terrain themselves. That gives you full freedom — and allows illogical things that are easy to miss on the plan: a portal in mid-air or a mountain missing under a bridge cannot be built like that.
How to fix it: Portal on the bridge: drag it to the end of the bridge or remove it. Mountain under the bridge: move the portal or the bridge. Bridge in a tunnel: put the bridge in the open valley or lower the mountain there. Opposite portals too close: pull them apart or remove one. Bridge too close behind the portal: move the portal and the bridge apart. Portal without a tunnel: turn it, place it at the mountain or remove it. A portal right at the edge of a bridge, facing the bridge, is fine — the tunnel opens onto the bridge there.
Numbers & defaults: a tunnel needs at least 26.8 cm between two portals (H0, scaled with the gauge); Trackplanner discards anything shorter — this also applies to the tunnel between a portal and a bridge. “In mid-air” means the track at the portal plane lies more than 1 cm above the terrain in front of it; up to 1 cm (H0) past the edge of a bridge, a portal still stands at the edge. The check is free.