How to Draw a Complete Road in AutoCAD from a Centre Line
Last updated 24 October 2026
From one polyline to a finished road plan with RoadPro: edges, turning radius, barricades or kerb, chainage, signs, markings, a cross section and an Excel report.
What you need
- Full AutoCAD, Civil 3D or Map 3D 2013 or newer. AutoCAD LT is not supported.
- RoadPro, a free plugin: one zip with RoadPro.lsp, the RP_PAVER hatch pattern and install notes.
- A drawing in metres (millimetre drawings work too: choose Millimeters under Drawing units in the dialog).
- The drawing saved first, because the Excel report is saved in the drawing's folder.
Load RoadPro once
- Type APPLOAD in the AutoCAD command line.
- Select RoadPro.lsp and click Load.
- RoadPro installs itself: it copies itself to AppData and joins the Startup Suite, so it loads in every drawing from then on.
- Type RDP to open the RoadPro dialog.
Draw the road
- Set the options. RDP opens the dialog with the defaults ready (below). Change what your job needs, such as the road width or the edge treatment, and press OK.
- Give the centre line. Pick points (arcs are allowed, Enter to finish) or select an existing line or polyline. In Civil 3D you can select an alignment.
- RoadPro builds it. The turning radius at every bend, both edges, the centre line, the road surface, barricades, cones or kerb stone along the edges, and chainage ticks and labels.
- Signs and ends: signs with their IDs, a tie-in or road-closed end, and lane arrows.
- The report: a summary on screen, the Excel file saved, and you place the report tables.
- The cross section: pick a point to place the typical section.
Press U once to undo the whole road, and F2 to see the summary and where the Excel file was saved.
The defaults worth checking
| Setting | Default |
|---|---|
| Road width | 7.30 m |
| Turning radius | Match existing, or 10 m at the centre line |
| Edge / centre | Barricades / centre lines |
| Barricade unit | 2.0 × 0.5 m, 0.5 m from the edge |
| Paved shoulder | 0.50 m |
| Chainage | Every 20 m |
| Speed limit | 30 km/h |
| Crossfall | 2.5% |
| Lane / median width | 3.65 m / 3.00 m |
At the centre line the turning radius must be more than half the road width, or the edges can't be offset round the bend.
After the road is built
- RDC adds lanes, a median, sidewalks, walkways with a paver hatch, drains and utility strips; RDU redraws them after edits.
- RDM draws the road markings: edge lines, the lane and centre line with its pattern set by speed, and lines at bends.
- RDER changes a curve's radius and rebuilds the road; RDB rebuilds it after you edit the centre line by hand.
- RDRAD and RDSEC label the curve data (TC, CT, C1 …) and the straights (S1 …) on the plan.
- RDX draws cross sections: the typical one, at a chainage, or at every interval.
- RDLX exports the centre line as a LandXML alignment for Civil 3D.
Joining roads and adding lanes are in road junctions, widening and turning lanes, and what the Excel report lists is in road quantities and setting-out data.
Before you rely on it
RoadPro draws to the values you give it; the design engineer confirms the road. Try a new version on a copy of a drawing first, and check the lane counts, drains and utility strips, which are geometric provisions rather than a design. The three-minute demo shows a full road built in Civil 3D.
Draw your next road with RoadPro