University of Novi Sad

FACULTY OF TECHNICAL SCIENCES

Basics of Automotive Engineering

Part five:

Forensics in Automotive Engineering

PhD Dragan Ružić, Assistant Professor

Department for Mechanization and Design Engineering

Chair for Engines and Vehicles

Part five:

Forensics in Automotive EngineeringForensics in Automotive Engineering

Purpose of the course:

• Presentation of the role of forensic engineering in area of motor vehicles and road trafficarea of motor vehicles and road traffic

• Explaining the importance of vehicle subsystems on trafic safety

• Introduction of vehicle forensic procedures and methods

Content of the course:

• Vehicle as a dangerous thing and the vehicle forensic engineering

Forensics in Automotive EngineeringForensics in Automotive Engineering

• Vehicle components and subsystems relevant for driving active safety

• Vehicle forensic procedure

• Basic characteristics of damaged parts and recognition of failure cause

• Presentation of case studies

Statistics shows decrease of fatal accidents despite of increase in number of vehicle, but accidents still happen.

Motor vehicle as a dangerous thing

In terms of fatality rate Serbia has now reached 84 dead per million inhabitants (red zone!), which is significant

Motor vehicle as a dangerous thing

which is significant improvement in comparison to year 2001 when the rate was 173!

ROAD FATALITY RATES 2014 (dead per million)

Source: European Commission: Road safety in the European Union

Trends, statistics and main challenges, March 2015

Investigation should to reveal the cause (or causes) and contributions to the traffic accident:

• human factor,

Motor vehicle as a dangerous thing

• human factor,

• vehicle: technical factor,

• environment: external factor (road, weather...),

• combination (very often)...

... but not always.

There are many other types of failures in vehicle's mechanical systems which cause only a damage with financial consequences. There is also necessary to find and approve the cause of failure.

Motor vehicle as a dangerous thing

The main questions in the case of the damage are

• who/what is responsible?

• how to avoid that the same failure occur again?

Forensic engineer = an engineer connected with legal investigations.

Forensic Engineer

If there is a court process (criminal or civil), the forensic engineer have a role of expert witness.

Examples of cases where the vehicle forensic engineers can be involved:

• traffic accident with fatal or non-fatal consequences

• damage on vehicle subsystem (engine, gearbox, body etc.)

• fraud (usually in insurance, used vehicle market, vehicle

Forensic Engineer

• fraud (usually in insurance, used vehicle market, vehicle ownership etc.)...

Vehicle components and Vehicle components and

Forensics in Automotive EngineeringForensics in Automotive Engineering

Vehicle components and Vehicle components and subsystems relevant for driving subsystems relevant for driving

active safety active safety

Wheels and tyres: the only way to obtain contact with the road

Braking system: slowing and stopping the vehicle and keep it still!

Steering system: changing the direction, important for avoiding

Vehicle components and subsystems relevant for driving active safety

Steering system: changing the direction, important for avoiding obstacles

Suspension system: connects wheels with the vehicle body and contribute to good contact between the tyre and road

Headlights and signalization: to see and to be seen!

Contact with the road: ensures braking and/or changing of direction, until maximum adhesion is reached

Tyre/road conditions determine the limit of adhesion.

Wheels and tyres

Examination includes:

1. Technical conditions of the wheels that could cause or contribute to the accident (proper size, type, tread

Wheels and tyres

accident (proper size, type, tread condition, maintenance, ...)

2. Signs of irregularities that could indicate what happened (sudden loss of

Wheels and tyres

happened (sudden loss of pressure, puncture caused by foreign object, blocked wheel(s)... often in combination with marks on the road)

video

To decelerate vehicle under all conditions (but total braking efficiency depends on the contact with road too!)

Indicators of poor condition of braking system

Braking system

Indicators of poor condition of braking system

• Brake fluid or air leak (that existed before accident)

• Overheated or greasy surfaces

• Broken or missing parts

• Insuficient braking forces measured on Roller Brake Tester(when available)

• Absence of any skid marks on the road (ABS?)

• Brake fluid leak (that existed before accident), "soft" brake pedal

• Overheated or greasy surfaces

• Broken and missing parts

Braking system

Broken and missing parts

• Braking forces measured on Roller Brake Tester (when available)

• Skid marks on the road (ABS?)

Braking system

There are two main "causes" of accident claimed by the driver when the driver did not change direction when he should:

• "The steering wheel was blocked!"

• "The steering wheel was turning freely!"

Steering system

"The steering wheel was turning freely!"

Inspection of mechanical connection between the steering wheel and the front wheels (video)

Inspection of servo assistance (power steering): pump drive, oil leak...

Steering system

Connects wheels with the vehicle body and contribute to good contact between the tyre and road.Parts of the suspension system are very often damaged in collision due to excessive irregular forces that were acting on the system.

Suspension system

Improves a visibility under poor light or night conditions

Whether the headlights (or stop light or indicator) were turned on in the moment of collision or not? Was it relevant?

Headlights and signalization system

Headlights are almost always destroyed in frontal collision!

1. Light bulb filament shape and/or colour

2. Old or new dirt inside the headlights

Headlights and signalization system

Headlights and signalization system

3. Headlight switch position

Additional findings

• Additional findings could be important for other kinds of forensic engineers or experts: tachograph reading, state of seat belts and airbags, seat position, instrument readings etc.

• Example is data from instruments that could be useful for traffic forensic engineers for space-time analysis and traffic forensic engineers for space-time analysis and determination the vehicle velocity in the moment of collision.

• Under the high acceleration (deceleration) inertia switch turns main electrical circuits off and instrument cluster are depowered.

• Step motors in speedometer and in rev-counter in most cases will stay in the position that corresponds to the moment of contact with an obstacle (or another vehicle). This often works on newer vehicles (depends on conditions), but not on works on newer vehicles (depends on conditions), but not on old vehicles with electro-mechanical instruments.

• Citroen C5 2.0 HDI: The value 85 km/h corresponds with engine speed 2250 RPM in fifth gear and this confirms the calculation of traffic forensic engineer about the vehicle speed in the moment of collision.

• Audi A8: The engine speed 4100 RPM does not corresponds to speed 150 km/h in any gear because the vehicle is equipped with automatic trasmission.

ForensicForensics in Automotives in Automotive EngineeringEngineering

Vehicle Forensic ProcedureVehicle Forensic Procedure

• Whole vehicle

• Parts of the vehicle

• Photographs, videos

• Documents (investigation reports, examination results, bills,

Types of evidence materials

• Documents (investigation reports, examination results, bills,etc)

Available evidence material depends also on the stage of the process.