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Analysis methods of AIB

​AIB’s analysis of the specific accidents has the aim of highlighting which conditions led to the accident occurring. There is no weight added to responsibility or legal offences, but naturally there is often a connection between clear offences and a significant percentage of the accident’s cause. The analysis is performed following a fixed methodology which is mainly unchanged since AIB's first theme analysis. By using a fixed methodology, the accidents are more uniformly and thoroughly analyzed, so that the analysis and conclusions do not stop with the most obvious explanations.
The main element of the analysis is illustrated in the figure “AIB’s analysis methods” and explained in more detail in the following.

Figure: AIB’s analysis method

Establishment of the events

Information processing procedure

Figure: Information preparation process





Establishment of the events
The first element in the analysis of the accident is to establish the events. The events are described, including significant conditions from the period before the accident, the conditions in the seconds up to the accident, such as avoidance manoeuvres, the collision and a description of the vehicles and the final positions of the parties.
AIB determines the most likely events from the collected data, including explanations from witnesses and those involved. An important tool in this process is the "PC Crash" programme in which various possible scenarios can be simulated. Emphasis is placed on conformity between the actual damages and injuries to vehicles and persons and the simulated injuries. Similarly the simulated movement patterns and the vehicles’ simulated final positions should conform to the actual conditions which are determined from the tracks left behind etc.
When the events have been identified, the conditions which led to the accident are identified. 

Information processing procedure
When the probable events have been determined, an analysis is performed in the road user’s "information processing" in the seconds immediately prior to the collision. The analysis is based on the model illustrated in the figure “Information preparation process”. This analysis methodology was originally developed in Sweden (TRK’s Accident Investigation Board. Reporting of a research assignment. Stockholm 1978), and the additional work by AIB.

The first step in the analysis of the information processing is to determine what the "important information", i.e. the information needed so that the accident could have been avoided. And determined when the information should have been gleaned. The information will typically be the signal the road user should have reacted to (if they had been seen and understood correctly). Often this will consist of a real danger signal, but not all parties in an accident have a danger signal.
The next step is to determine if the road user had access to the necessary information with enough time to avoid the accident. If the information was available, it must be investigated whether the road user noticed the information.
The last part of the model is an assessment of the road user’s decision and action; was it reasonable based on the information the road user had gleaned and processed.
The above review is made for all road users involved in the accident.


When the analysis of the information processing is complete, a general analysis is made of the individual element's significance for the accident’s cause and progress. Figure: Information preparation process

Influence of the elements
AIB sees accidents as a failure in the interaction between road users, vehicles and the road/surroundings. That is why a general assessment is made of these elements’ significance for the accidents. It is in this part of the analysis that there is a possibility to highlight the condition of the road design which could have prevented or alleviate in-considerate road user behavior. An assessment is also made of the significance of the speed.

Under road user, it is assessed whether their behavior or personality has deviated from ordinary road users in a manner which is could have promoted accidents. This may include a motorcyclist with an extensive history in the criminal register for both and traffic and criminal charges. If, in relation to the accident, his driving is totally indefensible, e.g. at very high speed, this information, together with other information from the analysis, could indicate a person thrill seeking with a generally high propensity for accidents.
Under the road’s significance it is assessed whether the road’s design or surroundings has contributed to the accident’s cause or progress.
Under the vehicle’s significance it is assessed whether any faults or deficiencies of the vehicles could have contributed to the cause or progress. The significance of the vehicles having better safety standards within selected areas, e.g. integral braking systems with ABS for motorcycles is also assessed.
The significance of speed is assessed in relation to the speed limit or in some cases in relation to a defensible speed which is suitable for the conditions. This may be the case on small winding country roads with poor visibility, where it has been concluded that speed should be adjusted to the surroundings.
If the speed was above the speed limit or not suitable for the conditions, it can be concluded that the accident could have been avoided if the limit/ the reasonable speed had been observed. If the accident would have happened anyway it will be assessed if whether exceeding the speed limit was significant to the personal injury.
If the speed’s significance is assessed, it is always based on the actual events. A calculation is made where the road user’s speed is changed to the speed limit at the location where he reacted to the second party/danger signal. Everything else remains un-changed. In practice, in most cases this is based on the valid speed limit.



Accident and injury factors
When the events have been determined and the information processing and the element’s significance is analyzed, it can be determined which factors led to the accident and which were significant to the extent of the injuries. AIB uses a limited number of possible factors and these are related to the analysis of information processing and the significance of the elements.  

  • Accident factor:
    An accident factor is an adverse factor without which the accident would not have occurred.
  • Injury factor:
    An injury factor is a circumstance which worsens the extent of personal injuries but has not caused the accident.
  • Underlying factors:
    An underlying factor is a clarification or an explanation of the determined accident and injury factors.

It should be noted that the factors are generally circumstances which should not be present in traffic. 



When accident factors are identified, it must be investigated which measures would in all likelihood have prevented the accident. Attention will be focused on the interaction between the road user, vehicle and road/surroundings. Road or vehicle measures will therefore be identified as solutions for road user related factors.

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