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Interactive 3D (Three.js)

Swept path screening at the E45

Lorries, modular road trains and buses drive through exit 52 Skanderborg V in 3D, and the demo checks each run against the swept path requirements of the Danish Road Directorate (Vejdirektoratet).

Role
Data, simulation and web development
Tools
  • Three.js
  • Claude Code
  • OpenStreetMap (map data)
Technology
WebGL
Format
Interactive, runs live in the browser
Interactive 3D, running live in the browser Open in new window
How to use the demo
  • Choose a manoeuvre and a vehicle in the panel on the right
  • Play the run, or drag the timeline
  • Switch between 3D and the 2D drawing
  • Click the vehicle's label to zoom in on it
  • Click a road to see its data
  • Save the run as PNG, or as DXF for MicroStation in the 2D view
  • Drag to rotate the camera, and scroll to zoom
The eastern junction and the E45 in 3D, only the terrain from the elevation model, without texture
The 3D model
The eastern junction straight from above on the 2025 aerial photo, with cars in the junction and shadows from the trees
From above

About the demo

The demo shows exit 52 Skanderborg V on the E45 in 3D. You choose a manoeuvre and a vehicle, and the demo calculates where the wheels and the body go and checks the run against the instruction on swept paths from the Danish Road Directorate (Vejdirektoratet). The aim is to show how an existing junction can be screened quickly for large vehicles.

The screening points to four places in the junctions

The screening points to four places where the articulated lorry, which is the design vehicle on state roads, goes further out than the instruction from the Danish Road Directorate (Vejdirektoratet) allows. The two right turns from the ramps are too tight, so the outline with the 0.3 m margin goes more than 1.5 m over the edge line at the corner. The left turn from Ry towards Aarhus goes 0.6 m over the kerb at the nose of the central island, and the left-turn lane towards Kolding is too narrow for the articulated lorry with the margin. None of the six manoeuvres fully meets the requirements. The markings are measured on aerial photos with 10-20 cm accuracy, so the findings are a starting point for a proper analysis.

Limitations

The screening is a proof of concept on open data and does not replace an analysis in AutoTURN or a survey. The markings are drawn from aerial photos with 10-20 cm accuracy, and several of the exceedances are only 0.1-0.3 m, so they lie within the uncertainty. The vehicles' dimensions are approximate, and the simulation has not been compared with AutoTURN. All three vehicles follow the same driving line, where a driver would place them differently. Lane lines are only checked in the junctions and the last 20 m or so of the ramps, and the bus is checked like the articulated lorry, because the instruction has no rules of its own for buses.

My role and the use of AI

Claude Code's little figure shuffling on the spot

The idea and the choice of exit 52 are mine, and the code was made with the AI tool Claude Code, which I directed. I decided which data to use, what the screening should show and how it should look. I set up access to Dataforsyningen, corrected markings and driving lines on the editing page and had errors fixed when the run looked wrong. I asked for a review against the instruction from the Danish Road Directorate (Vejdirektoratet), and it showed that the rule on lane lines was missing. With that rule, the result fell from 7 to 1 of 18. AI makes it quick to build a specialist tool, but it has to be checked against the standard.

What I have learned

I have learned how much open data there really is on Danish roads: terrain, aerial photos from several years, kerbs and traffic islands. It has made me curious to find more. The traffic light phases in the demo, for example, are guessed, because I had no data for them, and that is one of the things I would like to learn more about.

Manoeuvres
6, through two signalised junctions
Findings
4 places to look at more closely
Vehicles
Articulated lorry as the requirement, modular road train and bus as examples
Largest exceedance
More than 1.5 m over the edge line in the right turns
Check
Driving mode A, 15 km/h, 0.3 m margin
Status
Proof of concept on open data
DXF
UTM32, kerbs within 7 mm of GeoDanmark

The vehicles

Articulated lorry, 16.5 m: tractor unit with a 3.7 m wheelbase and a trailer with 7.7 m from the kingpin to the centre of the axle group. Modular road train, 25.25 m: lorry with a 4.8 m wheelbase, dolly and a trailer of the same type. Bus, 13.7 m, with a 7.0 m wheelbase. All are 2.55 m wide, and the dimensions are approximate. Only the articulated lorry is a requirement in the junction. Exit 52 is not part of the road network for modular road trains, and according to OpenStreetMap no bus route uses the ramps, so the modular road train and the bus are included as examples.

How it is built

Road network from OpenStreetMap, terrain, aerial photos, carriageway edges and traffic islands from Klimadatastyrelsen and GeoDanmark. The cars and shadows in the aerial photo are replaced by painted roads, and the markings are drawn from a median of seven years of aerial photos and stored as data that can be corrected. The tractor unit or the bus is calculated as a bicycle model. The front axle is steered towards the driving line in the middle of the lane with Stanley control, a steering method developed for Stanford's self-driving car Stanley, and the front wheels can turn at most 40 degrees. Towed units are pulled at the coupling, and their axle follows as a tractrix, the curve a dragged object traces. The calculation moves forward 10 cm at a time. The vehicles keep to their own lane through the junction and use the right-hand lane when the markings allow it. With the margin, the articulated lorry and the bus may not cross edge lines, lane lines, centre lines, hatched areas or kerbs; modular road trains have more lenient rules.

Technology and CAD

The demo runs in the browser with Three.js and downloads about 15 MB. The road surfaces and markings are calculated in advance, so it starts in a few seconds. In the 2D view the run can be saved as DXF in ETRS89 / UTM 32N with layers for kerbs, markings, driving line, swept path and conflict points.

Sources