# Help Needed to understand a Car Accident

• Automotive
LionCity
Dear All,

I was involved in a car accident. The facts of the case as follow:

Location: At a side road joining into a major road. The side road slopes downwards on a 10 degree gradient to the major road. My car was the first vehicle awaiting to exit into the major road.

Background of Accident: I felt a shudder from my car. Apparently, my vehicle was hit on the rear section by the second car driven by a Ms MJ.

Damages: There was severe damages to my car on the bumper about 0.3m wide. Suspected it was a point load acting on the flat bumper. There was no real damage to her car except noticed a ROUND indentation mark appearing on the bumper. There was a hard point in the form of a screw behind that bumper from subsequent investigation.

Claim by 2nd Driver: Ms MJ according to her report that I reversed up-slope and collided with her front causing her car to move backwards despite her applying her brakes fully and that she was in the fully stopped position with a reasonable distance behind me.

Question: I realized that in many accidents, the car that got hit hardly moved when the brakes were applied. I was trying to determine it was possible or not possible for my low powered Honda Hybrid reversing upslope to overcome her car's brake holding strength/inert weight to move her vehicle backwards. I checked out the accident area and I estimated the distance between my vehicle and her vehicle when in the stationary should not be more than 2 m apart.

I tried various methods from the internet and could not determine a fully satisfactory answer. Hope someone could help. Thank you very much.

Some info about the cars:

Honda Civic Hybrid: Weight about 1,380 kg and acceleration from 0 - 96 km per hr about 12.4 seconds.

Honda Fit: Weight about 1,200 kg and acceleration from 0 -96 km per hour about 9.3 seconds. Braking distance from 96 m per hr to 0 about 41m.

## Answers and Replies

Mentor
It would seem that the more logical explanation is that she hit you and not you hitting her especially considering that you were waiting to get on a highway. I'm assuming that you didn't in fact backup so I don't think you're going to be able to resolve this with an ad-hoc physics analysis.

Did you get a police report on the accident? Sometimes they will note who appeared to cause the accident in their assessment.

In any event, since its only damages then it looks like "no fault" applies here and your respective insurance companies will duke it out. In any evet, your policy may or may not increase based on your driving record.

jnnx
I doubt very much that your car would be able to push her uphill. maybe if you had some 2 ton 4x4 SUV with big engine...

LionCity
Thank you for your quick responses. I am in Asia so the way it is handled is different. Presently, I am preparing for a court proceeding. What angered me most was not the cost of the repairs but her dishonest conduct. I was entirely civil to her after the accident. Oh well...they are plenty of people on world that would sell their mothers for 2 dollars.

Anyway, I was working on this analysis for about a day and realized how limited my knowledge was and so decided to put something here.

What I used was kinematics to work out the expected velocity of a backwards reversing car with the average acceleration of a reversing Honda Civic with a travel distance of 2m. I assumed acceleration was constant. With the mass known, I determined the velocity at impact to be 10.55 km per hour. Even if I allowed the distance to be increased to 3m and that if I increased the acceleration by 50%, the impact velocity would have been just 15.83 km per hour. Even at this very conservative velocity, my senses indicated that I would be unable to move her car backwards.

However, liked what both jnnx and jedishrfu mentioned it was unlikely I would be able to push her uphill. Both cars have crumpled zones both front and rear that are meant to absorbed most of the impact velocity. Furthermore, we have the added mass of about 1,200 kg of the second car.

Any further insights would be much appreciated. Thanks again.

Mentor
I would argue your case that since you were about to enter the highway on a ramp the slopes downward why would you even back up. Its far more likely that she braked too late and hit you then use the limited crash analysis to bring home the case.

Common sense usually wins. In the US, she would most likely be liable because she had more control of her car. She either hit you or pulled up too close to your car either way she did the wrong thing.

A more common accident is when someone pulls out in front of your car and you can't brake fast enough and you hit them. Without a witness, you would most likely be cited for driving too close the car in front.

LionCity
Dear Jedishrfu,

I agreed with you that common sense usually wins. I just want to cover my bases well before the pending case. It has been on going for the past 18 months since the accident. It went through various meditation processes and I found er and their underwriters have been causing a lot of road blocks along the way and making terrible accusations against me including one that stated I had a previous damage. I caused the accident to make a claim against them. They added that I reversed and knock into some pillar or pole to cause the damages.

The day after the accident, her husband called me and said the damages were not serious and just wanted to knock it back (for heavens sake...). I asked him why he did not want to claim his insurance and he said that he did not want increased premiums for the following years. I could not accept his his half-baked repair offer.

But looking at the indentation and with my limited stress analysis experience, I though it was caused by a single point load from the screw on her bumper. All the forces from her car was transmitted through that screw causing my bumper and boot cover to crumple terrible. If it was a bumper to bumper collision, the forces would have been better distributed.

I could send a picture if anyone is interested in looking at it.

Thank you.

xxChrisxx
If you want a piece of advice. Don't even attempt to explain that your speed going backwards couldn't have caused the damage.

Attempting to argue that indicates (could be seen as an admission) that it was possible for you to have selected reverse and hit her car. I am that circumstance, reversing could have caused damage.

Trying to be too clever allows you to be picked apart and ends up backfiring. Leading to a 50/50 liability.

Its better to stick to facts, if you didnt reverse you just state you didnt reverse. Its up to them to prove you wrong. Its still your word against theirs, but road positioning and the type of collision should be in your favour.

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1 person
LionCity
Chris, I think what you said made sense. Ms MJ made a couple of inconsistencies in her statements and I will point it out (including the point you raise) to my lawyer and he decide whether to present or not .

Nevertheless, the research on this topic was quite interesting. To be honest, I felt quite down but the research into the accident has helped me feels better. The other route is to employ an accident specialist but it will cost probably more than 10,000. Money is always finite for most of us.

Thank you.

Highspeed
If any of your tail lamps/backup lights were broken during the accident, lookup info on lamp filament forensics.

1 person
LionCity
Dear All,

What I have done was to go on a long walk through various car parks and looking at various cars to see if they have similar damages. Found three cars with real damages. One thing I have found in all three cases was that the damage line slop say about 25 to 30 degree to the vertical and the dent radiates outwards from the line.

In one case, the damage on its rear was quite similar to my car. I intend to talk to the driver to see I can get more details of his/her accident.

The other thing I intend to do is to go to the accident reporting centre to see if there are other similar cases.

Kind Regards