Overpass Builder

Give a busy junction a way over or under. Select an existing road or rail crossing, choose which pair of approaches goes on the bridge, and adjust the deck and ramps before building. The live preview shows the proposed geometry as you work.

• Road and rail crossings: road over road, road over rail, rail over road and rail over rail, including supported parallel-track layouts.
• Choose the over-axis by clicking a coloured ring dot or one of its paired segments. Junctions need at least four connected segments and enough room for the ramps.
• Overpass and underpass presets provide starting values. Fine-tune bridge length, deck height, ramp slope, under-road drop and the gradient back to ground in the construction bar.
• Live preview and build checks: inspect the deck and approaches before committing. Build becomes available when the preview passes validation; unsupported geometry stays unbuilt.
• Bridges matched to the crossing: choose from available stock bridges or let Auto select a compatible deck for the road or railway.
• Town-building demolition is included: ordinary town buildings in the bridge path are removed in the same proposal. A rejected bridge does not demolish them first.
• Controller support: aim and confirm to select the junction and axis, open the toolbar for settings and Build, and follow the contextual shortcut hints.
• Existing networks are checked: protected constructions, one-way streets and affected segments with signals, stops, waypoints or decorations are refused. Keep a save before substantial edits; the README lists supported layouts and limits.