Calculate vehicle speed based on impact results?

[Tom Brokaw]

I hope I'm not asking too much.

Other Driver hit Family Member. I want to calculate how fast OD was going. Desired results would be accurate to within 5 MPH or less.

OD was in a 2003 Hyundai Elantra; googled curb weight around 2700.
FM was in a 2005 Nissan Titan; googled curb weight around 5000.
Impact was on passenger side rear axle of the Titan.

Titan was spun approximately 180 degrees and passenger side was lifted off the ground. I'm don't have specifics on that yet, such as did the curb stop the spin and therefore cause the truck to start a rollover, or did the impact generate the lift and the spin came to a "natural" stop? Police report indicates the Hyundai scraped the road, causing damage to the street surface. I don't have more specific info than that.

Dry asphalt. Almanac.com provided the following temps on the day in question:
Minimum
37.4 °F

Mean
41.4 °F

Maximum
48.2 °F

The accident occurred on a March afternoon in a northern latitude an hour prior to sunset, so temps should not have fallen too much.

I'm sure more info is needed but I don't know enough to know what that is. Any help appreciated.

 

[rcgldr]

Accident investigations are very complicated. Energy is lost to deformation of the cars. Momentum is lost unless you include the relatively tiny effects on the relatively massive earth. How much energy is consumed by the brakes and tires depends on how much braking was involved and how much sideways sliding was involved.

 

[Tom Brokaw]

Thanks for the reply.

No braking was involved. The only sliding that I'm aware of is the arced motion of the rear truck wheels.

What other info should I gather? Or is there simply too much?

 

[rcgldr]

There are a lot of details involved. Weight distrubtion of the vehicles, coefficient of friction for the tires, did the tires hop or did other body parts of the car scrape the ground which would affect friction coefficient. I'm not sure how suspension plays a roll in the reaction to a collision. How much deformation occurred, ...

 

[PJC01]

I would first like to say that it is important to note that calculating vehicle speed based on impact results can be a complex and challenging task. There are many variables that can affect the accuracy of the calculation, and it is important to gather as much information as possible in order to make an informed and accurate estimation.

That being said, based on the information provided, here are some steps that can be taken to calculate the vehicle speed:

1. Determine the impact speed: The impact speed is the speed at which the two vehicles collided. This can be estimated by measuring the distance between the point of impact and the final resting position of the vehicles, and dividing it by the time it took for the impact to occur. This can be determined from eyewitness accounts or by analyzing the damage to the vehicles.

2. Consider the weight and type of vehicles: The weight and type of vehicles involved in the collision can also affect the impact speed. The heavier the vehicle, the more force it will have upon impact. In this case, the Hyundai Elantra weighs significantly less than the Nissan Titan, which could have an impact on the final speed calculation.

3. Take into account the angle of impact: The angle at which the vehicles collided can also affect the impact speed. A direct head-on collision will result in a higher impact speed compared to a glancing blow.

4. Consider the road conditions: The condition of the road, such as the type of surface and any obstacles or debris, can also affect the impact speed. In this case, the impact resulted in damage to the street surface, which could have slowed down the vehicles and affected the final speed calculation.

5. Use physics equations: There are various physics equations that can be used to calculate the impact speed based on the variables mentioned above. One of the most commonly used equations is the conservation of momentum equation, which takes into account the masses and velocities of the vehicles before and after the collision.

However, it is important to note that even with all of this information, it may not be possible to calculate the exact speed of the other driver. There are many factors that can affect the accuracy of the calculation, and it is always best to consult with a professional accident reconstruction expert for a more precise estimation. I hope this helps.