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3D SITE RECONSTRUCTION: VISIBILITY OBSTRUCTION
BACKGROUND – A vehicle traveling westward on King Edward Avenue struck a pedestrian who was crossing the road to get to a bus stop. The driver of the vehicle stated that his visibility was obstructed due to traffic control equipment on the side of the road.

OBJECTIVE – Check the impact that the placement of the traffic control equipment had on the driver’s line of sight by generating a three-dimensional digital environment and observing the sight line of the driver in two instances: (1) when the traffic control sign is positioned in such a way as can be seen in photographs, and; (2) when the traffic control sign has been moved further from the edge of the road.

1. Scan The Intersection
The first step in generating an accurate digital environment is to collect the physical data. A digital environment can be produced using references such as scene photographs, survey data, satellite/aerial imagery and police reports. Spatial data collected by 3D laser scanning is particularly comprehensive and provides a rich and accurate foundation for digital reconstruction.

In this example, a 3D scan was conducted of the intersection at King Edward Avenue and Cartier Street in Vancouver BC. Because the scene was scanned at a later time than when the photographs were taken, the traffic control sign and hazard signs that were present when the accident occurred were unavailable at the time of the scan.



Above: video flythrough of scanned environment.

2. Extracting Road Surface for Engineer Analysis

Once the scene has been scanned, detailed spatial information can be extracted from the scan data as needed in a variety of formats which can readily be imported into an engineer’s technical software to assist with analysis. Scan data can also provide new or additional measurements, or verify the accuracy of an engineer’s initial measurements.

In some cases it may not even be necessary to send an engineer to visit the site at all. The scan data is performed independently of opinion analysis and can be referred to various experts for analysis.

In this example, the topography of the road was exported for an engineer’s analysis. The profile of the road was reconstructed in 5 meter intervals, providing a highly precise surface for the engineer to input into accident reconstruction software, ex. PC-Crash. As a result, the engineer was able to verify the accuracy of his initial measurements against the scan data and evaluate his analysis accordingly.

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Above: wire frame of road surface data. Sections of scan data can be exported in a variety of formats for engineer analysis.

3. Reconstruct and Place Key Features – Traffic Control Equipment


Above: Traffic control sign was reconstructed and placed into the digital environment to match what was observed in the photographs.

Using the scan data, it is possible to precisely locate any characteristics or features that are present in photos but are no longer available at the scene, e.g. vehicles, obstructions, skid marks, road features. Once located, features and objects in the photograph can be accurately reconstructed.

This technique is especially useful to explore and present visibility issues, as it enables the opportunity to “step into the scene” and view the scene from any perspective.

In this case, the electronic sign and surrounding striped barricades were reconstructed, located and placed precisely in the digital environment.

4. Place 3D Models Into Scene
Computer-generated models are imported in to the scene; in this case, a vehicle matching the specific make and model of the accident vehicle and a human model representing the pedestrian.

Additional data can be imported from an engineer’s technical software to generate dynamic motion, such as a path of movement for the vehicle.


Above: Computer-generated models are imported and placed into the digital environment.

5. Alternative Scenario – Move Traffic Equipment Back
The ability to visually experiment with different scenarios in an interactive three-dimensional environment allows early identification of any potential strengths and weaknesses, and case strategy can be modified accordingly. In this example, a “what-if” scenario was generated where the traffic control equipment was moved further back from the edge of the road towards the center of the median, approximately one meter from it’s original position.

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Above: Reconstructed traffic equipment in it’s original position (left); traffic equipment moved away from the edge of the road (right).

6. Compare Driver’s Line of Sight

In this case, the objective was to find out if the placement of the traffic control equipment had an impact on the sightline of the driver. The images below compare the driver’s line of sight in two instances: first, when the traffic control sign is positioned in such a way as can be seen in photographs; and second, when the traffic control sign has been moved approximately one metre inwards from the edge of the road.

Below: Two images comparing the driver’s line of sight.

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