In Search of Delta-V (∆V)
On the Scene E-Newsletter, Edition 125, October 20, 2010
When reconstructing accidents, Delta-V is a critical piece of the puzzle. Delta-V, the long standing metric of crash severity, is simply defined as the total change in vehicle velocity over the duration of the crash event. Delta-V is traditionally estimated through crash reconstruction techniques, “crunching numbers”, either manually or using computer codes. However, traditional methods are limited. Crash test data can allow an engineer to determine whether a given accident had a Delta-V that was greater or less than in the crash test, but does not necessarily indicate the exact magnitude of the Delta-V. Thus, while bounding provides valuable information regarding the severity of an accident, it leaves plenty of room for improvement – there’s a vast difference between concluding that the Delta V in a crash was 2 mph versus bounding as being less than 8 mph.
Delta-V can also be somewhat difficult to estimate in many types of collisions including sideswipes, collisions with narrow objects, and angled side impacts because of the increased number of variables introduced. In these cases engineers and accident reconstructionists must be even more conservative with their estimates, providing an even greater range of velocities and forces. This greater range, again increases the ambiguity that can be derived from the data. This inability to determine precise figures is very important because, when estimating crash severity, the more precise a Delta V that can be determined, the more precise an engineer can be in determining crash severity and injury causation. Many times with the traditional methods one cannot rule out bounded Delta-V’s with ranges of 8-10 mph.
There are other methods of determining Delta-V that can provide much more precise values. One of these is actual testing. If and when appropriate, component testing can be a powerful tool for the accident reconstructionist. Now, exact vehicles or vehicle components can be tested in the same configuration as the in subject accident. As a result, the engineer can now determine with far more precision the forces and velocities that occurred in an accident. Instead of having to provide loosely bounded figures, we have entered the realm of being able to ascertain specifically quantified velocities.
In order to obtain more precise values of Delta-V’s, CED engineers have developed the skills and experience required to appropriately test the components involved in various types of accidents. By recreating the damage on components such as bumpers, side view mirrors and trailer hitches, CED engineers have been able to determine Delta-V’s with much more precision than if they had relied solely on traditional methods. Instead of being bounded by a Delta-V less than 10 mph, they’ve been able to determine a Delta-V was 0-2 mph.
This is a powerful tool, for with more precise Delta-V’s comes more precise analysis of damages and injuries. For more information on CED experts, please visit our website at www.cedtechnologies.com OR contact one of our regional offices to speak with a case specialist.