Time Sequence Analysis is one of the most useful techniques used in accident reconstruction.

This type of analysis is used to determine the locations of each vehicle or a pedestrian relative to each other at a particular point in time.  Usually, calculations in 1/4 or 1/2 second intervals are sufficient in most of the time sequence analyses, but any time increment can be utilized depending upon the requirements of each case.

Almost always, a scale diagram is used to locate the positions of the vehicles or pedestrians in the Time Sequence Analysis.

A Time Sequence Analysis is most commonly used in the following types of Accident Reconstruction cases:

1. Failure to yield the right of way from a Stop or Yield sign or failure to yield the right of way of a vehicle that is turning left where the reaction time of a driver that had the right of way needs to be analyzed.
2. In cases where a line of sight obstruction is present in the concerned quadrant of the intersection, the Time Sequence Analysis can determine where a vehicle was located just prior to its entry into the intersection and whether or not it was observable to the approaching driver.  It is not uncommon for a land owner to be a defendant in these types of cases.
3. A pedestrian crossing the road is another common case for a Time Sequence Analysis.  The technique can address the period of time required for a pedestrian to move from a position of safety to a position of peril?

An accident reconstruction expert can also use a Time Sequence Analysis in conjunction with an Avoidance Analysis.

Because time, distance & speed are the concerns that an accident reconstructionist must deal with in most every case, the Time Sequence Analysis can be a most valuable accident reconstruction technique.  By utilizing a Time Sequence Analysis, an expert can determine precisely such factors as the time to get from point A to point B, time for avoidance, distance back from impact, or available stopping distance.

The Time Sequence Analysis can provide answers to critical questions such as:

How much hazard time is involved?

Does an approaching driver have the opportunity to see the other vehicle or pedestrian?

Does the driver have enough distance to avoid the vehicle or pedestrian?

By utilizing this technique, the accident reconstruction expert can reconcile and determine the answers to these questions.

Ask any accident reconstruction expert about driving hazards, and standing water, puddles, are right on the top of the list.  In fact, puddles can be a real danger to drivers.  It’s all about vehicle dynamics.

Puddles are created by water that has accumulated in the road because of the run-off caused by the crown of the road.  These puddling areas are usually several feet into the travel lane of the road adjacent to the road edge and can be a few feet long to perhaps 10,12, 15 ft. or more in length depending how much it has rained.  Sometimes these puddles are a few tenths of an inch deep and they could be a 1/2 inch or more in depth.  

The driving hazard presented by standing water is explained by basic vehicle dynamics.

When a vehicle is traveling down the road it will, “wants”,  go straight ahead unless an outside force acts upon the vehicle. To be specific, the center of mass wants to continue on its forward path.

So assume that a vehicle encounters a puddle that is partially in the travel lane, and partially off to the right of the road.  Let’s take a look at the vehicle dynamics. 

As the right front tire enters the puddle, the water becomes a retarding force that acts upon the right side of the vehicle.  This retarding force causes the vehicle to rotate in a clock-wise manner.  The clock-wise rotation will cause the vehicle to be pulled to the right and most likely off the road.

The danger is that the vehicle may impact an object on the shoulder of the road if the driver cannot regain control of the vehicle. Another possibility is that the driver will overcorrect and sharply turn the steering wheel back to the left and possibly go head-on with an oncoming vehicle.  Talk about a driving hazard!

Have you been involved in an accident?  Do you have a case?  Should you call an attorney?  Maybe it would be a good idea to have your accident evaluated first.

Are you an attorney with a prospective client who desires an accident reconstruction evaluation before your proceed? 

Or, perhaps you are uncertain if you really need accident reconstruction to develop your case. 

Are you an insurance professional who needs a case evaluation prior to proceeding with a particular defense?

In any of these scenarios, at this point all you need right now is an evaluation of your accident case.  You need some questions answered.  You could get it done in an hour … if only this was possible.

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Now I can direct my experience to you by way of my 1 hour consultations.  Designed for professionals and accident victims alike, this service provides you with an evaluation of your case, and how or if you should proceed.  For attorneys, it can mean whether or not to sign up the client.  For victims, it can mean whether or not you should proceed with legal representation.  Regardless of the circumstances, the service is designed to help you in an efficient, reasonable manner.

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Most of the vehicles today are equipped with an anti lock braking system which is commonly called an ABS braking system.  What this system does is to allow the brakes to rapidly pulsate in order to decelerate a vehicle,  instead of completely locking up the brakes in what is called a panic mode of deceleration.

Here are some of the significant differences between an anti lock braking system and a non-ABS braking system and how each affects  panic deceleration and braking distances.

Non-ABS braking system:

Loss of steering control during hard application of braking.

Once the brakes are locked in a non-ABS vehicle, the driver can no longer steer the vehicle.  The driver can turn the steering wheel to the right or to the left but the vehicle will not respond to those steering inputs.  In other words, the vehicle is going to continue to travel in the direction it was going at the moment the brakes are locked. 

A driver cannot steer out of a hazardous situation with a non-ABS braking system in a panic mode of deceleration.  If a driver desires to steer he would have to “unlock” the brakes.  That means that a driver would have to release some of the pressure on his brake pedal in order to regain his steering capabilities.

The only factor that will influence stopping for a Non-ABS vehicle during a panic mode of deceleration (skidding) is the interaction between the tire and the road.  This interaction likewise increases braking distances.

 ABS braking system:

The pulsating action of ABS brakes prevents the brakes from locking as opposed to a non-ABS braking system.  The brakes do all the work to decelerate the vehicle as compared to only the tire-road interface of a non-ABS vehicle. 
 
The pulsating action of an ABS braking system has some real advantages.

An ABS equipped vehicle can achieve higher rates of deceleration than a non-ABS vehicle.  That means that those vehicles can come to a stop in less distance than a non-ABS vehicle, thereby reducing braking distances.

A driver can steer his vehicle during hard application of brakes.

So, what is the downside to an ABS equipped vehicle?

The ABS braking system allows a driver improved control of his vehicle and reduces stopping distances on dry and slippery roads, but on loose surfaces like gravel or snow-covered pavement, an ABS system can  notably increase braking distances.

A potential problem with an anti locking braking system is that during a panic mode of deceleration, the driver can over steer.  For example, a violent steering input while braking in a panic mode can potentially send the vehicle across the road into oncoming traffic.

 How can accident reconstruction work for your case?

Another accident reconstruction technique that is used to determine speed calculations at impact is crush.  I will only use a crush technique in certain circumstances, i.e. a pole impact, a barrier wall impact or a tree impact.

In  a crush speed calculation technique you also need the weight of the vehicle and what is called a stiffness co-efficient.  Every vehicle has a different stiffness co-efficient.  Furthermore, in a crush technique one must calculate exactly how much actual crush is sustained by the vehicle.

This is easier said than done and this is why.  Many years ago, vehicles had front bumpers that were perpendicular to the center line of the vehicle.  In cases involving those earlier model vehicles an accident reconstruction expert could easily determine the crush to the vehicle just by measuring the crush on the vehicle itself.

However, in their infinite wisdom to increase gas mileage, one of the things that the automobile manufactures decided to do was to put curvilinear bumpers on the vehicles.  In other words, all automobile bumpers now have a bumper that is slightly curved. 

Consider this.  If you were to measure a vehicle starting at the rear and measure it down the center line to the front of the vehicle you would get a measurement of the overall length of the vehicle.  But if you were measure from the rear to the let’s say only to the right front corner of the vehicle you would see that your measurement is substantially less than the overall length measurement you obtained that was down the center line.  In fact, the measurement would be different all the way across the bumper because the bumper is curved.  This is because of free space, and it signifies the difference in the overall length of the vehicle depending where on the bumper you take a measurement.

This brings us to the problem of determining how much actual crush the vehicle sustained. 

In a case involving a vehicle that impacted a pole, a tree, or a wall, an accident reconstruction expert must  measure the crush depths and locations of the crush on the accident vehicle.  In order to obtain the actual crush depth of the  accident vehicle, the accident reconstruction expert must measure an exemplar vehicle to reconcile the crush depths of the accident vehicle with the specific areas on the exemplar vehicle. 

Then, and only then, can an accident reconstruction expert apply the actual crush measurements into speed calculations.

Unfortunately, inexperienced experts and investigators often misinterpret crush damage measurements, which can result in highly inaccurate speed at impact calculations.

How is accident reconstruction working for your case?

I discussed previously the effect of weight and weight variables in a momentum equation.  Another variable in a momentum formula are the angles of departure.

Long ago during an arbitration hearing I was working the plaintiff side of an Uninsured Motorist case with $4 million in coverage involving a fatality.

Testimony at the arbitration hearing indicated that both myself and the opposing expert had the same impact location, the same final rest location, and essentially the same post-collision speeds.  But, of note, we had calculated substantially different speeds at impact. 

The arbitrators called me back to explain how it was possible that two accident reconstruction experts had the same data but vastly different speeds at impact. 

I explained to the arbitrators that the difference was in the angles of departure of one of the vehicles. 

The opposing accident reconstruction expert measured the angle directly from impact to final rest as opposed to specifically reconciling the actual angle of departure.
 
On the other hand, my momentum equation included direct input from the police traffic homicide investigator.  During our meeting on the scene, I had questioned the officer about the minute details of his investigation.  While reviewing his notes, I had observed a diagram that depicted a specific angle of departure that was different than the angle assumed by the opposing expert.  The officer was able to confirm the angle based on the input data in his investigative file.

The differences in a real angle of departure as opposed to an assumed angle of departure dramatically impacted the results.  More specifically, as I explained to the arbitrators, it was the angle of departure that accounted for the huge differences in our respective speed at impact momentum formula calculations.

Result:  The arbitrators awarded $4 million to my client, the plaintiff.

A professional accident reconstruction expert must often rely on a momentum formula as a technique for calculating speeds at impact.

One of the variables in a momentum formula is the total weight of each vehicle – including the weight of any objects in the vehicle.

In cases where I utilize a formula for momentum, if my client has not provided the weights of the occupants I will customarily assign an average weight such as 150 lbs for a female occupant and 200 lbs for a male occupant.  Over the years, I have found that these weights are substantially accurate for momentum purposes.

However, one day during the course of a trial while I was on cross examination the opposing attorney asked, “If the variables in your formula change, would your speeds at impact change?”  I said they would, but any changes would depend on the degree of change to a specific variable.

The attorney asked me to assume for the purposes of recalculation that the female plaintiff weighed 380 lbs and not the 150 lbs as I had assumed for my original calculations.  

I indicated that if the court would give me a few minutes I could recalculate using a momentum equation.  The judge agreed.  It was apparent that the judge was also interested in the outcome of a 130 lb weight increase. 

By hand, and while on the witness stand, I recalculated by inputing the new weight into the momentum formula. 

I testified that the calculation, with a difference of 130 lbs, resulted in only a 1.3 mph difference in the previously calculated speed at impact. 

The results were no surprise to me, however the attorney was stunned.  He asked if I could have made a mistake.  He wanted me to re-calculate.  I did.  The answer remained the same.  The jury had heard the same bad answer twice – he lost.

I believe physical evidence interpretation is almost always the single most important aspect of professional accident reconstruction.  Think about it, if an accident reconstruction expert cannot analyze the physical evidence, how can he apply the laws of science and mathematics?

Once the physical evidence has been identified and interpreted, an accident reconstructionist frequently turns to time, distance and speed analysis.

Speed is expressed in miles per hour (mph) or feet per second (fps).  Some of the formulas that an accident reconstructionist will use deal in mph while other formulas will generate an answer in fps.  An expert must be very careful to distinguish the two when he is conducting his analysis, or when responding to a question at a deposition or at trial. Certain calculations require that the expert must convert mph to fps in order to arrive at a correct answer.  It is imperative that the accident reconstructionist calculates the appropriate conversion.

To demonstrate this point, I recall a time when a young accident reconstructionist was caught in the “heat of the battle” during cross examination at trial.

The expert was asked to assume that a vehicle was going 45 mph and was 3 seconds back from impact.  The question was how far was the vehicle from impact at that time.  The expert said 135 feet.  (45 mph x 3 ft. = 135 ft.). 

The attorney was sharp and he was prepared.  He knew that the 135 foot distance calculation was incorrect.  In response, the attorney posed a similar question.

He asked the expert to assume the vehicle was going 45 mph and was 4.5 seconds back from impact.  The expert answered 202.5 feet back from impact.  (45 mph x 4.5 seconds  =  202.5 ft.).

The attorney knew from his pre-trial planning with his own expert that the formula in question required that speed had to be converted from mph to fps.  He knew from the second answer that the opposing expert had not calculated the necessary conversions into his analysis.

The correct way to calculate feet back from impact would have been to covert 45 mph to 66 fps and then multiply by the time.  So let’s take a look at what the answers should have been.

1.  45 mph is converted to 66 fps  x 3 seconds back from impact and that would equal 198 feet back from impact.

2.  45 mph is converted  to 66 fps x 4.5 seconds back from impact and that would equal 297 feet back from impact.

As you can see, there is a substantial difference between what the expert testified to and what the answers should have been. Regrettably,  the accident reconstruction expert could not answer even the most basic of questions relating to time, distance and speed.   Unfortunately, his client lost.

Accident reconstruction can provide the ultimate support that you need for a successful conclusion to your case.  More often than not, time distance and speed calculations can make or break that case. 

How is accident reconstruction working for you?

An accident animation can work well – in selected cases.  Assuming the animator and the accident reconstruction expert work together, computer animations can provide just what a jury needs to better understand your case.

What an accident animation should NOT do is to make a non-event an event.

In recent years I have been retained on many occasions to provide my expert opinion regarding what the insurance industry terms, staged accidents.  As you might well know, a staged accident, (or a caused accident), involves reports of injury-causing accidents and insurance claims where the vehicles did not make contact – at least not with one another.

An accident reconstruction damage and physical evidence analysis can determine if the evidence supports the facts of the case as presented.

Some time ago I had the pleasure of working for a very good defense firm regarding a number of these types of cases.  One case in particular had become very contentious.  Out of exasperation, my attorney client called me with an idea.

Now bear in mind, my physical evidence analysis had revealed opinions that were beneficial to the defense in this particular case.  The evidence spoke for itself.

But for some obscure reason, the defense was concerned.  In hopes of bolstering their case, there was a proposal to secure an accident animation for trial.  What?!

The thought pattern was that from the computer animation, the jury could see “how the accident did not happen.”

Could I have been listening to the impossible?  An accident animation could never depict my findings.  Supported by strong physical evidence, it was my opinion that the accident did not happen.  There was nothing to animate!

The plan was to use an animator to show the vehicles approaching and impacting in a manner contrary to the physical evidence.  Like too many others of these non-science-based accident animations, we were on the verge of a cartoon!

What a gift for the plaintiff!! The defense was making preparations to demonstrate that the accident did, in fact, well … happen!

Recall I described this as a very good defense firm.  They saw the light.  There was no accident animation for an accident that did not happen.

And the jury agreed.

Are you using accident reconstruction to build your case?