Easy Method for Collecting Vehicle Crush Profile Data

by scolburn 26. March 2021 14:36

By: Steve Colburn, Applications Training Specialist, Laser Technology, Inc.
Photos and case study data courtesy of: Rich Maxwell

Today’s Crash Investigator makes use of all possible data sources at their disposal when reconstructing an incident. The more information that can be analyzed by the team, the more confidence they have in their assessment of the situation. Most of this data is collected with mapping tools and photography in short order right at the scene so it can be cleared quickly. However, some data like vehicle crush profile is typically not due to the time and personnel resources it requires. This specific data set is essential for determining the maximum engagement between two vehicles, which contributes to finding the principal direction of force. It is also very useful for putting vehicles together in scaled diagrams and showing the sequence of the crash.

When measuring crush on a vehicle by manual methods, the tools required to do the job can be inexpensive items like tape measures and simple levels. There are also more expensive jigs or gauges, from manufacturers such as Saker, that can be used to outline the damage. These must be purchased in different sizes and have fixed intervals at which you can measure. Two operators are required to hold each end of the tool, whether it is a tape measure or one of these gauges, using up valuable personnel resources. Additionally, all the data must be recorded by hand, making it prone to transcription errors. As is usual when delineating crush, one axis is set up laterally across the extent of the damage and then measurements are taken to the vehicle along another at right angles to it. Much care needs to be taken to keep everything square, adding to the time this method requires to complete. In many cases, using manual tools like this can produce excessive error in the results, rendering the data useless to the investigator in the end.

Here is where high-tech comes in to play. A much better method is to use a total station type device, that measures horizontal and vertical angles, as well as distance to the target. These instruments do require a little bit of training but can be very simple to operate. And a single operator can collect all the data necessary, making best use of the available manpower. After a short setup procedure with the total station and software, data points along the line of crush on the vehicle can be collected in seconds. The operator can now capture more data, at whatever interval they choose, instead of being restricted to a fixed spacing. Perhaps one of the biggest benefits of this method is the accuracy it provides. Using very simple precautions, the operator can collect data that is more precise than the manual method and the survey is performed with very little risk of error. The investigator can have complete confidence in the results of a vehicle crush profile measured properly by a total station-type instrument. Scanner technology from manufacturers such as Trimble and Leica can gather very precise crush data but the high cost, more complex procedure and sheer magnitude of data that must be processed makes them impractical for this application. Although slightly more expensive than the complicated jigs, simple total stations make short work out of what can be a difficult measurement scenario.

The following case study demonstrates all the benefits of this easy to operate, high-tech method for measuring the crush profile on a vehicle that has been involved in a crash. The total station system in use is the TruPoint 300 product from Laser Tech and their flagship data collection app, QuickMap3D. This system is fully capable of recording all the important measurements for crush profile down to mm-level accuracy.

Access to the front of this vehicle where the damage in question occurred was already present, so moving a vehicle to gain sight to the entire extent of the damage was not necessary. It is always best to visibly mark the point of maximum impact and construct a 2D plane of measurement across the boundary of the deformation. In this case a strip of blue tape was used. The total station is positioned at a comfortable distance away from the vehicle so that the operator may walk in between them without risk of bumping the instrument. It should be positioned in a spot where all the significant surfaces of the damage can be seen with a clear line of sight. Next, a Backsight point is established nearby where the horizontal angle can be referenced to begin the survey and then checked after when complete for quality. Now in a matter of minutes, hundreds of data points could be collected if necessary, with just the single operator. In this case, approximately 40 points were taken along the 2D plane that was marked. Other critical points of reference on the vehicle important to the crash investigator may be gathered at this time as well. These can be the corners of the body or more importantly, the axles or center of the wheels - which are critical in when comparing the data collected to an exemplar vehicle.

If the spots happen to be out of direct sight of the total station, a target pole may be used to accurately locate points of evidence hidden from view. If more than one side of the vehicle has sustained damage that needs to be measured, the total station can be easily moved to another point and the survey of other crush areas continued. In this manner, all the points will be properly joined in the field and no stitching together of two data sets will be necessary later.

After the vehicle crush profile data is checked for quality in the field, it can be imported directly into any popular CAD based (or other) diagramming software. Above on the left, the raw data is displayed showing the crush profile as well as the body and axle points collected. Next we see a close up of the damage area and the exemplar vehicle overlaid on top of the crush with the reference points at the axles accurately aligned. The Crush measurement spacing can now be calculated based on the width of the damage, 2” in this case, and then measuring the corresponding displacement values using a CAD program. This data is then fed into the equations for determining speed from crush. In addition, the “to-scale” profile can be imported for use in the scaled diagram. When two vehicles are involved, crush profiles will help to put them together at maximum engagement and show the principle direction of force.

There is no doubt that a crush profile of a vehicle can be an extremely useful piece of the puzzle for the Crash Investigator. Today’s high-tech mapping method, using a simple total station system, makes the job of collecting this critical data quick and easy. Now this important piece of evidence can be gathered with a minimum impact on valuable resources.

See how Laser Tech’s products make crush measurement easy. Contact LTI.


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