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Road Crash
Reconstruction:
Today the society rightly
expects that “safety is the right of humans”. Can we establish a safe
environment system to reduce road crashes? For this it is essential to
track and understand the vehicle crashes happening on the road. By doing
crash reconstruction one can understand the causes of occurrence, and the
mechanism of vehicle damage as well as human injury. We may then propose a
safer design to vehicle manufacturers, improve safety devices on vehicles,
improve road conditions and move towards a scenario WITHOUT INJURIES FROM
ROAD TRAFFIC CRASHES. Thus, crash data collection and reconstruction is
used to improve vehicle crashworthiness and improve safety of road users.
The objective of crash
reconstruction is to estimate the collision sequences / parameters that
best fit the damaged vehicles, data found at the scene as well as witness
statements and depositions. The reconstruction of a crash gives a realistic
model of the event by adopting a systematic approach. The data collected at
accident site is used as input and used to develop a computer simulation of
the event.
Sequential positions of vehicles during the crash
In our work, we have been analyzing crashes and
reconstructing them using software like MADYMOTM and PCCrashTM.
Since a large number of crashes in India involve Vulnerable Road Users
(including pedestrians, bicyclists, motorized two / three wheeler riders),
some of our work is oriented towards crashes involving VRUs. The steps that
are followed for crash analysis and reconstruction are as follows:
- Investigation of the crash site
- Measurement of details on the
crash site
- Collection of data
- Making Scaled drawings
- Modeling of vehicles, pedestrians
and vehicle – occupants
- Computer simulation and
optimization
Investigation of the crash
site
In order to get a realistically reconstructed event, it
is necessary to obtain data to the minutest of the detail possible. This
can only be achieved by thorough observation and complete examination of
the crash site. At the time of collection of the data, the site of crash
may not remain as it was at the time of crash. This is more so in the
Indian scenario as after a crash, the first responsibility of the police as
well as the public is to clear the vehicles and get the traffic moving; in
the process a lot of crucial evidence is lost. The job of the
reconstructionist thus becomes very difficult. He has to ensure that he
reaches the site as soon as possible after the crash and painstakingly take
care of every relevant evidence and data and record it. Typically, the
police is the agency, which first get the information of the occurrence of
a crash. In our data collection efforts, in the past we have collaborated
with these agencies, obtained information regarding the site of crash form
them and amanaged to reach the site within 30-45 minutes so as to gather as
much data as possible. The data collected from the site includes careful observations
and measurement of the initial point of impact, point of final rest, and
positions of debris etc. These observations serve as an input in the
subsequent steps.
Measurement of details on the crash
site
Typically, a reference point is established at the site
of crash which serves as a reference point from which all the measurements
are to be taken. Some of the important items, which are measured from the
site of crash, are listed below:
- Skid marks of the colliding vehicles
- Point of Impact
(POI) of the colliding vehicles
- Final resting point of the vehicles
- Location and details of debris found on the site
- Details of vehicles parked in the vicinity of the
site
- Positions of speed breakers around the site
- Lane marking on the roads
- Road dividers
- Poles and traffic lights on and near the crash
site
- Buildings and walls
- Hoardings and other related information.
Collection of other data
After the
proper measurements have been taken it is very necessary to collect and organize
other data into an understandable form. To work on this, data from all
possible sources are collected, to gain full insight into the event, like
from
- The police reports
- The medical report
- Interviews of witnesses
- Interviews of victims
A typical crash site showing a wide
variety of data important for reconstruction
Drawing of the site of crash
The next step is to arrange the collected and recorded
data into a representation, which depicts the situation in a reasonable
manner. For this, a reduced scale drawing is prepared with a suitable scale
to accommodate the drawing on one paper. All the details, which have been
collected with proper dimensions and measurement, are drawn on the paper.
This serves as a preliminary sketch for the final simulation work.
Modeling of vehicles, pedestrians and
vehicle – occupants
While using
software like PC–Crash we can use different models of vehicles, pedestrians
etc. that are available with the software. However, if any new type of
vehicle is to be simulated, then it’s modeling needs to be done. For this
the various dimensional parameters are to be changed to generate a new
model of the vehicle. The modeling of pedestrians and vehicle-occupants are
done on a case-to-case basis. This means that a general model available in
the package can be modified to generate different models for people with
different features like for example height, weight etc.
Computer simulation
and optimization
The different
data collected like initial point of impact, direction of motions of
colliding bodies before and after the collision, point of rest of the
colliding bodies, positions of debris, skid marks etc. are used to obtain
the approximate initial velocities and directions of the colliding
vehicles. Apart from this, the make and model of the vehicles, the surface
conditions of the road, coefficient of friction of the road etc. are also
necessary for the simulation and analysis. All these parameters are
initially estimated but the simulation of the event does not necessarily
agree with the crash data known. These parameters in simulations are then
iterated so as to get a reasonable match of the known crash data.
The final (post crash) positions of the vehicles as
obtained from a simulation tool (PCCrashTM)
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People Involved:
Faculties:
1. Dr. A. Chawla
2. Dr. S. Mukherjee
3. Dr Ahmed Ali Hassan (Birmingham Automotive
Safety Centre, University of Birmingham, UK)
Students and Staff:
1. Devendra
2. Varun Grover
3. Ganesh Kakade
4. Lalaram
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List of Sponsored
Projects:
1. Studies
of Road Traffic Crashers and Injuries in UK, Sponsored by the UK India
Education and research Initiative (UKIERI), Co-PI: Prof S Mukherjee.
2. Safety
Modeling and Epidemiological research, sponsored by Volvo Research
Foundation, PI: Prof D Mohan.
3. Study
of scientific investigation and analysis of road accidents in Delhi,
Sponsored by Ministry of Road Transport and Highways, Government of
India, Co-PI: Prof S Mukherjee.
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Related
Publication:
- S
Mukherjee, Chawla A, L Patel, A road crash reconstruction technique,
Vol 91, July 2010, Institute of Engineers Journal, pp 3-8.
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