SAFETY CONCEPTS

Automotive safety
When developing new vehicles it is emphasized that the vehicle meets the safety requirements. These requirements are set by valid regulatory acts, but also by customers
needs. In addition, vehicle manufacturers themselves are developing a variety of safety
features that are intended to increase the safety of the vehicle. The main purpose of vehicle
safety is life and health of the vehicle crew, but also other road users (pedestrians, cyclists, other vehicles, etc.). In general, the goal is to minimize the likelihood of an accident
and if this occurs, to ensure protection of health and life. To achieve this goal it is possible
to apply different features that can be called safety of the vehicle.

The term safety of the vehicle means two basic categories of safety: active and passive
safety.

Active safety

It refers to devices and systems that helps to keep the vehicle under control and prevent an accident. These devices are usually automated to help compensate for human error -- the single biggest cause of car accidents.

Classifications of active safety:

1. Driving or travel safety
2. Conditional safety
3. Perceptual safety
4. Operating safety


1. Driving safety
It is the result of a harmonious chassis and suspension design with regard to wheel suspension, springing, steering and braking, and is reflected in optimum dynamic vehicle behavior.


2. Conditional safety
It is affected by psychological state (of the driver), which depends on the comfort, visibility, vibration, noise and climate impacts.
Visibility – the better driver sees surrounding traffic conditions, the lower is the risk of unexpected situations.
Vibration – affects the driver and result as disturbance (into frequency range of 1-25 Hz
stuttering, tremors etc. falls also vibrations).
Noise – is manifested as audible disturbance when driving the vehicle. It can comes from within (engine, gearbox, shafts, axles) or outside (tyres, road and wind noise). Vibration and noise impact the concentration of the driver. Good sound insulation and well-balanced suspension cab reduces the noise levels, therefore can reduce the risk of road accidents.
Climatic conditions are the air temperature, humidity, air flow and air pressure. Pleasant climate in the car keeps the driver in good condition and ready, even during long journeys. Good heating, ventilation and air conditioning are important for supporting
high standards of vehicle safety.


3. Perceptual safety
The level of safety which increases the perceptual security, focuses on lighting equipment, audio warning devices, direct and indirect view of another vehicle.

4. Operating safety
-relaxed driver (driving without stress), as well a high level of driving safety, requires an optimal design for the driver's surroundings with respect to its comfort. Safety and comfort are interlinked in many aspects. Driver who sits comfortably, has a good posture and easy to read, easy to understand and reach ergonomic devices and controls, can better manage and better concentrate on the surrounding traffic conditions. 

The driveline also has an important role. A vehicle that provides good management capacity in terms of electronic engine management, or even automatic transmission, puts less stress
on the driver.

Overview of active safety

1. Anti-lock brakes prevent the wheels from locking up when the driver brakes, enabling the driver to steer while braking.
2. Traction control systems prevent the wheels from slipping while the car is accelerating.
3. Electronic stability control keeps the car under control and on the road.
4. Adaptive cruise control-adjust the vehicle speed based on the traffic environment
5. Tyre pressure monitoring system monitors the air pressure inside the pneumatic tyres.
6. Lane departure warning system warns the driver when the vehicle is moving out of its lane.
7. Night vision system extends the perception of the driver beyond the limited reach of headlights
8. Blind spot detection system detects other vehicles located to the driver's side and rear.
9. Driver monitoring system is to monitor the driver's attentiveness while driving.
10. Road sign recognition system notify and warns the driver of enforced restrictions on the road.
11. Electronic Brake-force Distribution distributes the electronic brake power
    optimally between front and rear axles.
12. Intelligent suspension – automatically adjusts ride height according to speed and road conditions.
13. Warning system- Signaling of opened door, seat belt warning..etc. 

Passive safety
Passive safety includes all the features and measures in the vehicle that minimize
the consequences of an accident or prevent it. Passive safety is especially important when
the driver cannot actively intervene in the affairs of the road anymore.

Classifications of passive safety:

1. Interior(internal) safety
2. Exterior(external) safety

Exterior(external) safety

The term "exterior safety" covers all vehicle-related measures which are designed to minimize the severity of injury to pedestrians, cyclists and motorcycle riders struck by the vehicle in an accident. 
Those factors which determine exterior safety are

• Vehicle body deformation behavior
• External shape of the car body

The primary objective is to design the vehicle such that its exterior design minimizes the consequences of a primary collision (a collision involving persons outside the vehicle and the vehicle itself). The most severe injuries are sustained by passengers who are hit by the front of the vehicle, whereby the course of the accident greatly depends upon body size. The consequences of collisions involving two-wheeled vehicles and passenger cars can only be slightly ameliorated by passenger-car design due to the two-wheeled vehicle's often considerable inherent energy component, its high seat position and the wide dispersion of contact points. Those design features which can be incorporated into the passenger car are, for example:

• Movable front lamps,
• Recessed windshields wipers, 
• Recessed drip rails, 
• Recessed door handles.

Fig. presents the risk to pedestrians in event of collisions with passenger cars as a function of impact frequency and seriousness of injury (based on 246 collisions).

Interior(internal) safety
The term "interior safety" covers vehicle measures whose purpose is to minimize the accelerations and forces acting on the vehicle occupants in the event of an accident, to provide sufficient survival space, and to ensure the operability of those vehicle components critical to the removal of passengers from the vehicle after the accident has occurred.

The determining factors for passenger safety are: 

• Deformation behaviour (vehicle body),
• Passenger-compartment strength, size of the survival space during and after impact, 
• Restraint systems, 
• Deceleration systems,
• Control systems, 
• Deliverance of passengers, 
• Fire protection.

Overview of active safety 

1. Air bags (front, window, side, knee, front to rear passengers) - prevent the collision
   of the body, respectively individual body parts of the steering wheel, instrument panel and other interior parts of the vehicle absorb shock and reduce the risk of injury
2. Seat belts hold passengers in place so that they aren't thrown forward or ejected from the car. 
3. Rollover bars protect the car's occupants from injury if the vehicle rolls over during an accident.
4. Passenger safety cell 
5. Crumple zones – reducing the impact of the collision while designing their body structure. 
6. Whiplash protection- backrest prevent the driver and passengers from getting whiplash during a rear-end collision. 
7. Child safety system-specifically designed seats that protect children from injury or death during collision.
8. Belt bags
9. Collapsible steering column – in case of an accident it reduces the driver’s risk of hitting the steering wheel.
10. FPS (Fire Protection System Safety) – a system which blocks the supply of electricity and fuel in case of an accident, to avoid the risk of fire.
    

 

Deformation behavior of vehicle body
Due to the frequency of frontal collisions, an important role is played by the legally stipulated frontal impact test in which a vehicle is driven at a speed of 48.3 km/h (30 mph) into a rigid barrier which is either perpendicular or inclined at an angle of up to 30° relative to the longitudinal axis of the car.

Because 50 % of all frontal collisions in right-hand traffic primarily involve the left-hand half of the front of the vehicle, manufacturers worldwide conduct left asymmetrical front impact tests on LHD vehicles covering 30-50 % of the vehicle width. Picture shows the Distribution of accidents by type of collision, Symbolized by test methods yielding equal results in a frontal collision, kinetic energy is absorbed through deformation of the bumper, the front of the vehicle, and in severe cases the forward section of the passenger compartment (dash area). Axles, wheels (rims) and the engine limit the deformable length. Adequate deformation lengths and displaceable vehicle aggregates are necessary, however, in order to minimize passenger-compartment acceleration.

Depending upon vehicle design (body shape, type of drive and engine position), vehicle mass and size, a frontal impact with a barrier at approx. 50 km/h results in permanent deformation in the forward area of 0.4- 0.7 m. Damage to the passenger compartment should be minimized. This concerns primarily dash area (displacement of steering system, instrument panel, pedals, toe-panel intrusion), underbody (lowering or tilting of seats), the side structure (ability to open the doors after an accident).

Acceleration measurements and evaluations of high-speed films enable deformation behavior to be analyzed precisely. Dummies of various sizes are used to simulate vehicle occupants and provide acceleration figures for head and chest as well as forces acting on thighs. The side impact, as the next most frequent type of accident, places a high risk of injury on the vehicle occupants due to the limited energy absorbing capability of structural components, and the resulting high degree of vehicle interior deformation. The risk of injury is largely influenced by the structural strength of the side of the vehicle (pillar/door joints, top/bottom pillar points), load-carrying capacity of floor cross-members and seats, as well as the design of inside door panels.

In the rear impact test, deformation of the vehicle interior must be minor at most. It should still be possible to open the doors, the edge of the trunk lid should not penetrate the rear window and enter the vehicle interior, and fuel-system integrity must be preserved. 

Roof structures are investigated by means of rollover tests and quasi-static car-roof crush tests. In addition, at least one manufacturer subjects his vehicles to the inverted vehicle drop test in order to test the dimensional stability of the roof structure (survival space) under extreme conditions (the vehicle falls from a height of 0.5 m onto the left front corner of its roof).

Fig. Inverse drop test

Fig.Acceleration, speed and distance traveled, of a passenger compartment when impacting a barrier impacting a barrier at 50 km/h.

 Speed and acceleration characteristics of vehicle body: 

Velocity graph for 15 mph barrier test

Velocity graph for 20 mph barrier test

Velocity graph for 40 mph barrier test

Velocity graph for 50 mph barrier test

All the graphs show the reduction in velocity (speed) of passenger compartment on impact. For 15 mph and 20 mph barrier test, we can see that the velocity comes to zero, crosses zero line, stays in the negative region afterwards. Velocity in negative region means that the car is moving in opposite direction (i. e.) after the collision it moves back. But for 40 mph test, the velocity comes close to zero and lies in the positive region. It means that after the impact, the car does not bounce back much, because most of the energy of the crash is taken by deforming the body metal. But in 15 mph and 20 mph tests, as the speed is low, the kinetic energy to deform the body metal is also less and hence the body metal does not deform and stands rigid. So, the car bounces back and velocity is slightly in the negative region.

Pedestrian safety

Pedestrian injuries 
The pedestrian kinematics and injuries in vehicle collisions are influenced by the impact
speed, type of vehicle, stiffness and shape of the vehicle front (such as the bumper
height, bonnet height and length, windscreen frame), age and size of the pedestrians,as well as the initial posture of the pedestrian relative to the vehicle front.

The main factor for measuring the severity of vehicle-pedestrian impact is the impact speed. In approximately 70% of crashes, the driver braked before the pedestrian was hit. Almost 95% of all pedestrian accidents occurred at an impact speed lower than 60 km/h, as shown in Figure . Pedestrians struck at impact speeds less than 25 km/h usually sustain minor injuries. Serious injuries occur frequently at speeds of 25-55 km/h whilst at speeds greater than 55 km/h pedestrians are most likely to be killed. According to a study, 79% of the pedestrians were in motion, and in 85% of the cases the pedestrians were hit laterally (37% at the right side, 48% left). 

Injury distribution by body segments

 Injury distribution by body segments

The injury frequency of the pedestrian body segments has been investigated since the
1960s in numerous studies by researchers from different countries.

Distribution of injuries by body regions of pedestrians struck by the front of cars

(N- injury numbers)

Pedestrian impact responses
The pedestrian responses to vehicle collisions are rather different for various vehicle front shapes. When an adult is struck by a passenger car front, the first contact occurs between the bumper and either the leg or knee-joint area, followed by thigh-to-bonnet edge contact. The lower extremity of the body is accelerated forwards and the upper body is rotated and accelerated relative to the car. Consequently, the pelvis and thorax are impacted by the bonnet edge and top, respectively. The head may hit the bonnet or windscreen at a velocity estimated as a ratio of 0.7-0.9 to the car-travel speed for big-car bonnet impacts and 1.1-1.4 for small-car head-windscreen impacts. Injuries are usually caused by a direct impact to body segments and a force transmission through the body segments.

The representative distribution of the injuries to an adult pedestrian in frontal

car-pedestrian collisions, trajectories of the head with respect to small and big cars,

changes of the locations of the head impact at varying impact speeds and the

wrap-around distance

hb- bumper height, hp-pedestrian height, he- leading edge height

Pedestrian safety features

1. Automatic braking
2. Emergency automatic braking 
3. Advanced infotainment 
4. Improved headlights 
5. Modified design of the bonnet

Severity Index

The Acceleration Severity Index (ASI) is used to evaluate the potential risk for occupant in full-scale crash tests involving roadside safety hardware. Despite its widespread use across Europe, there is a lack of research relating this metric to occupant injury in real-world collisions. Recent installation of Event Data Recorders (EDRs) in a number of late model vehicles presents a different perspective on the assessment of the validity of occupant risk based on the Acceleration Severity Index. EDRs are capable of electronically recording data such as vehicle speed, brake status and throttle position just prior to and during an accident.

Using measured vehicle acceleration information, the ASI is computed using the following relationship:

Human Impact Tolerance 

This is the area of study in impact bio-mechanics and is closely tied to rule-making as well as the design of dummy instrumentation to ensure that the parameters measured are in the injury range. It is also the most difficult area of study because of the large variation in mechanical properties of human tissue due to age, gender, weight and geometry. All of these factors are in addition to the normal biological variation in tissue strength and the acceptable level of injury.For example, frontal crashes do not cause serious neck problems unless the deceleration is very high. However, minor rear-end collisions can result in long-term neck pain. There are several levels of tolerance. These levels range from the“Ouch” level for volunteer subjects to the LD (Lethal Dose) 50 level at which half of the subjects would suffer a fatality. 

To define a reasonably safe level for the average car occupant without having to make the car unaffordably expensive, a moderate to severe level of injury is chosen as the tolerance level. That is, the injuries sustained by the average occupant should not be life threatening. There is an Abbreviated Injury Scale (AIS), developed by emergency room physicians and physicians in other medical specialties to quantify the severity of an injury to each body area. Severity is defined as threat to life and is not based on disability or impairment. On the AIS scale, any injury greater than AIS 4 is life threatening. The severity levels of AIS are explained in Table.

abbreviated injury scale

Determination of Injury thresholds for various Human body parts

1.Head Injury Tolerance

The Head Injury Criterion (HIC) was developed based on the linear acceleration of the skull, impacting a rigid surface. This value may range from 5,000 to over 10,000 rad/s² . The comparison of measured values supplied by the dummies with the permissible limit values as per FMVSS 208 (, chest acceleration: 60 g/3 ms(1 g is the average gravitational acceleration on Earth, the average force, which affects a resting person at sea level. 1 g = 9.80665 m/s² = 32.17405 ft/s²), upper leg force: 10 kN) are only limited in their applicability to the human being.

2.Neck Injury Tolerance

Neck tolerance is defined in terms of the various modes of loading.

1. Tolerance of the Neck In flexion-Extension 
2. Tolerance of the Neck in Extension 
3. Tolerance of the Neck in Lateral Bending

3.Thoracic Injury Tolerance

Frontal thoracic tolerance can be expressed in terms of acceleration or displacement.

1. Frontal Thoracic Tolerance
2. Lateral Thoracic Tolerance

4.Tolerance of the Abdomen

The current criteria for frontal impact are either impact force or compression. Since it was difficult to cause injury to abdominal organs, animal data were used as the basis for abdominal injury limits.

1. Tolerance of the Abdomen to Frontal Impact
2. Tolerance of the Abdomen to Side Impact

5.Tolerance of the Pelvis

Frontal tolerance of the pelvis does not appear to have been measured directly. The injury from lap belt loads, in the absence of an airbag, indicates that pelvic tolerance is relatively high for frontal impact. At present, the accepted criterion is a 10 kN impact force limit for male and 4.6 kN for female.

1. Tolerance of the Pelvis to Frontal Impact
2. Tolerance of the Pelvis to Lateral Impact

6.Tolerance of the Lower Extremities

1.  Tolerance of the Femur 
2.  Tolerance of the Patella 
3.  Tolerance of the Knee 
4.  Tolerance of the Tibia  
5.  Tolerance of the Ankle

VEHICLE ERGONOMICS

Ergonomics

The word “ergonomics,” the science of work laws (or the science of applying natural laws to design work), was coined by joining two Greek words: “ergon” (work) and “nomos” (natural laws). The field of ergonomics emerged in the European countries around 1949 to improve workplaces and jobs in the industries, with an emphasis on biomechanical applications. It improves performance, that is, it reduces operation/task completion time and errors, reduces learning and training, and makes products more enjoyable, less difficult, and less boring.

Ergonomics is a multidisciplinary science involving fields that have information about people (e.g., psychology, anthropometry, biomechanics, anatomy, physiology, psychophysics). It involves studying human characteristics, capabilities, and limitations and applying this information to design and evaluate the equipment and systems that people use.

International Ergonomics Association (IEA) defined Ergonomics (or human factors) as the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance. 

The basic goal of ergonomics is to design equipment that will achieve the best possible fit
between the users (drivers) and the equipment (vehicle) such that the users’ safety (freedom from harm, injury, and loss), comfort, convenience, performance, and efficiency (productivity or increasing output/input) are improved.

The field of ergonomics is also called “human engineering,” “human factors engineering,” “engineering psychology,” “man–machine systems,” or “human–machine interface design.”

Automotive Ergonomics:  
Automotive ergonomics focuses on the role of human factors in the design and use of automobiles. This includes analysis of accommodation of driver and/or passengers; their comfort; vision inside and outside of the vehicle; control and display design; pedal behaviour, information processing and cognitive load during driving etc.

This will discuss various physical aspect of occupant packaging for providing comfortable driving posture, clearance dimensions, proper view field, easy reach of the controls etc. to the driver.

 

History of Ergonomics in Automotive Product Design

1918: SAE issued J585 standard on tail lamps and J587 standard on license plate                           illumination devices.
1927: SAE issued J588 standard on stop lamps.
1956: Ford Motor Company established the Human Factors Engineering Department.
1965: SAE published J941: motor vehicle driver’s eye locations (eyellipse) recommended
          practice.
1966: Congress passed safety acts: National Traffic Safety and Motor Vehicle Safety Act                and the Highway Safety Act.
1969: National Highway Traffic Safety Administration (NHTSA), Department of                                transportation published notices of proposed rule making in crash avoidance area                  (e.g., vehicle lighting).
1976: SAE published J287: driver hand control reach recommended practice.
1978: NHTSA enacted Field of View Requirements on Motor Vehicles (Federal Motor                      Vehicle Safety Standard [FMVSS] 128 which rescinded later in 1979).
1984: Touch CRT introduced in cars (GM’s Buick Riviera).
1986: Center high mounted stop lamp required on all vehicles.
1997: Toyota launched “Prius” (hybrid electric vehicle with state-of-power display).
1997: NHTSA published a report on investigation of the safety implications of wireless                    communications in vehicles.
2000: Adjustable pedals introduced in the U.S. market on light truck products.
2000: NHTSA hosted the first Internet forum on driver distraction.
2001: Smart headlamps introduced in luxury vehicles.
2007: Ford introduced “sync” to connect cell phones and iPods and other USB-based                      systems.
2007: Rear seat entertainment systems with display screens available for rear passengers              were introduced.
2010: Capacitive touch-screen technology introduced in vehicle displays.
2011: Plug-in electric vehicles expected to be sold in the U.S. market by major automotive              manufacturers with power consumption gauges (eco-gauges).

Anthropometry and Bio-Mechanics

The process of vehicle design begins with a discussion on the size and type of the vehicle and the number of occupants that the vehicle should accommodate. To assure that the required number of occupants can be accommodated, the designers must consider the dimensions of drivers and the passengers and their posture in the vehicle space.

Anthropometry can be defined as the measurement of human body dimensions. Static anthropometry is concerned with the measurement of human subjects in rigid, standardized positions (e.g. static arm length being equivalent to its anatomical length) and static anthropometric data are used in designing equipment for the workplace where body movement is not a major variable, e.g. seat breadth, depth and height. Dynamic anthropometry is concerned with the measurement of human subjects at work or in motion (e.g. functional arm reach is a factor of the length of the upper arm, lower arm and hand, as well as the range of movement at the shoulder, elbow, wrist and fingers). Dynamic anthropometric data can be used to establish control locations using reach envelopes for the hands and feet and locations of head restraints, seat belts and air bags using data concerning the arcs described by various parts of the body under crash conditions. Biomechanics is the measurement of the range, strength, endurance, speed and accuracy of human movements and such data are also used in the design of controls to establish satisfactory ranges of control movement and operative forces.

Biomechanics deals primarily with dimensions, composition, and mass properties of body segments, joints linking the body segments, muscles that produce body movements, mobility of joints, mechanical reactions of the body to force fields (e.g., static and dynamic force applications, vibrations, impacts), and voluntary body movements in applying forces (torques, energy/power) to external objects (e.g., controls, tools, handles). It is used to evaluate if the human body and body parts will be comfortable (e.g., internal forces well below strength and tolerance limits) and safe (avoidance of injuries) while operating or using machines and equipment (or vehicles).

Anthropometry in vehicle design
Automobile is designed as per the anthropometry of the targeted user population. Measurement process can be broadly classified into two categories.

1. Conventional Static Measurements: The measurements taken on human body with the subjects in rigid, standardized position (fig). They are typically length, width, height and circumferences. These measurement includes standing height, seated height, seated eye height, upper leg length, knee height, seat length, upper and lower arm length, reach (total arm length), shoulder width, hip or seat width, weight, etc. These measurements are referenced to non-deflecting horizontal or vertical surfaces supporting the subject.

2. Functional Task Oriented Measurements: The measurements are taken with the human body dimensional co-ordinates x, y, z with respect to body land marks as reference points at work or motion in the workspace (fig). Typically they are represented in three dimensional co-ordinates x, y, z with respect to body land marks as reference points.

Anthropometric and biomechanical data are usually specified in terms of percentiles. The population is divided into 100 percentage categories, ranked from least to greatest, with respect to some specific type of body measurement. 

For example: 

• 5th percentile stature is a value whereby 5% of the population are shorter and 95% are taller;
• 50th percentile stature is the median stature; 
• 95th percentile stature is a value whereby 95% of the population are shorter and 5% are taller.

Cockpit design

The design goals of the seating position are:

• To enable the driver (and co-driver) to see clearly ahead and beside themselves through standard and peripheral vision.
• To provide a position of comfortable leverage for the driver so they do not become tired due to operating the controls from an awkward position.
• To enable the driver to adequately see the side mirrors in their peripheral vision (At a minimum) so that the driver need not continuously take their eyes off the road ahead to gauge an opponent’s position behind them. Ideally the side mirrors should be far enough forward to enable direct viewing by a driver glancing at them.
• To enable easy visual access to gauges and other visual feedback in the forward looking line of sight.
• To minimize CG height to optimize handling.

Design of driver seat

Seat Track Travel Limit
Seat track travel limit is decided in such a way so that individuals with smaller body dimensions as well as larger body dimensions can seat comfortably on the seat and can access all the controls including accelerator, break and clutch. Seat track travel limits in forward-backward and upward-downward direction are decided as per operational requirement.Figure depicts forward-backward movement of the seat as per the different percentile driver selected seat position (SAE- J1517). The foremost and rearmost hip points on the seat track define the seat track length. It should be long enough and placed at a horizontal distance from the ball of foot on the accelerator pedal of 2.5 percentile to 97.5 percentile hip point locations (defined as X2.5 and X97.5 in SAE J1517 and J4004). Based on the SAE J4004, a seat track length of about 240 mm would be needed to accommodate
95% of the drivers in passenger cars.

 

The reference points used for location of the driver and their relevant dimensions are described below.

1. The accelerator heel point (AHP) is the heel point of the driver’s shoe that is on the depressed floor covering(carpet) on the vehicle floor when the driver’s foot is in contact with the unpressed accelerator (gas) pedal .SAE standard J1100 defines it as “a point on the shoe located at the intersection of the heel of shoe and the depressed floor covering, when the shoe tool (specified in SAE J826 or J4002) is properly positioned (essentially,with the ball of foot (BOF) contacting the lateral centre line of the unpressed accelerator pedal, while the bottom of shoe is maintained on the pedal plane).

2. The pedal plane angle (A47) is defined as the angle of the accelerator pedal plane in the side view measured in degrees from the horizontal. The pedal plane is not the plane of the accelerator pedal, but it is the plane representing the bottom of the manikin’s shoe defined in SAE J826 or J4002.

3. Ball of Foot (BOF) on the accelerator pedal is the point on the top portion of the driver’s foot that is normally in contact with the accelerator pedal. The BOF is located 200 mm from the AHP measured along the pedal plane.

4. The pedal reference point (PRP) is on the accelerator pedal lateral centreline where the BOF contacts the pedal when the shoe is properly positioned (i.e., heel of shoe at AHP and bottom of shoe on the pedal plane). SAE standard J4004 provides a procedure for locating PRP for curved and flat accelerator pedals using SAE J4002 shoe tool. If the pedal plane is based on SAE standards J826 and J1516, the BOF point should be taken as the PRP.

5. The seating reference point (SgRP) is the location of a special hip point (H-point) designated by the vehicle manufacturer as a key reference point to define the seating location for each designated seating position. Thus,there is a unique SgRP for each designated seating position (e.g., the driver’s seating position, front passenger’s seating position, left rear passenger’s seating position). An H-point simulates the hip joint (in the side view as a hinge point) between the torso and the thighs, and thus, it provides a reference for locating a seating position. In the plan view, the H-point is located on the centreline of the occupant.

The SgRP for the driver’s position is specified as follows:

a. It is designated by the vehicle manufacturer.

b. It is located near or at the rearmost point of the seat track travel.

c. The SAE (in standards J1517 or J4004) recommends that the SgRP should be placed at the 95th percentile location of the H-point distribution obtained by a seat position model (called the SgRP curve) at an H-point height (H30 from the AHP specified by the vehicle manufacturer). 

6. The seat track length is defined as the horizontal distance between the foremost and rearmost location of the H-point of the seated drivers. 

A number of interior package dimensions shown in the previous slide are described in this section. The dimensions are defined using the nomenclature specified in SAE standard J1100. 

1. AHP to SgRP location: The horizontal and the vertical distances between the AHP and the SgRP are defined as L53 and H30, respectively.

2. Posture angles: The driver’s posture is defined by the angles of the HPM(H-Point Machine) or the HPD(H-Point Design). The angles shown in the previous slide are defined as follows:

a. Torso angle (A40). It is the angle between the torso line (also called the backline) and the vertical. It is also called the seat back angle or back angle.

b. Hip angle (A42). It is the angle between the thigh line and the torso line.

c. Knee angle (A44). It is the angle between the thigh line and the lower leg line. It is measured on the right leg (on the accelerator pedal).

d. Ankle angle (A46). It is the angle between the (lower) leg line and the bare-foot flesh line, measured on the right leg.

e. Pedal plane angle (A47). It is the angle between the accelerator pedal plane and the horizontal.

3. Steering wheel: The centre of the steering is specified by locating its centre by dimensions L11 and H17 in the side view. The steering wheel centre is located on the top plane of the steering wheel rim. The lateral distance between the centre of the steering wheel and the vehicle centreline is defined as W7. The diameter of the steering wheel is defined as W9. The angle of the steering wheel plane with respect to the vertical is defined as A18. 

4. Entrance height (H11): It is the vertical distance from the driver’s SgRP to the upper trimmed body opening (see Figure below). The trimmed body opening is defined as the vehicle body opening with all plastic trim (covering) components installed. This dimension is used to evaluate head clearance as the driver enters the vehicle and slides over the seat during entry and egress. 

 

5. Belt height (H25): It is the vertical distance between the driver’s SgRP and the bottom of the side window daylight opening at the SgRP X-plane (plane perpendicular to the longitudinal X-axis and passing through the SgRP; (see Figure below). The belt height is important to determine the driver’s visibility to the sides. It is especially important in tall vehicles such as heavy trucks and buses to evaluate if the driver can see vehicles in
the adjacent lanes, especially on the right-hand side. The belt height is also an important exterior styling characteristic (e.g., some luxury sedans have high belt height from the ground as compared with their overall vehicle height). 

 

Spatial Arrangement:

After defining the position of the driver on the seat, all other interior and structural components inside the vehicle are arranged accordingly with the intention to provide sufficient clearance dimensions around him/her. This process relies on human factor database. Larger anthropometric data (95th percentile value) are generally considered for this purpose.Spatial arrangement includes the positioning of driver’s seat and passenger’s seat in the allocated space inside,arrangement of various controls/components according to seating arrangements.

Legroom(L33):
The sufficient space for keeping legs of the driver/passenger in a comfortable position in an automobile. Proper legroom enables drivers to access structural component with ease. There should not be any obstacle to keep feet comfortably and at the same time for accessing controls like pedals (break/accelerator/clutch).

 

 Measurement of horizontal distance between H-Point and AHP is useful for this purpose. Care should be taken to ensure that any parts of lower body like thighs/knees should not touch with steering wheel or dash board or any other component. It is the maximum distance along a line from the ankle pivot centre to the farthest H-point in the travel path, +254 mm (to account for the ankle point to accelerator pedal distance), measured with the right foot on the undepressed accelerator pedal

Headroom(H61):

The height. It is the vertical clearance space above the head of driver/passenger in an automobile. A minimum 5.0cm head clearance for jolt in a vehicle is recommended (Galer 1987, Woodson et al. 1992). In vehicular workstation, available head clearance must be sufficient for wearing and removing the helmet in seated posture in seat. It is the distance along a line 8° rear of the vertical from the SgRP to the headlining, plus 102 mm (to account for SgRP to bottom of buttocks distance.

Shoulder room(W3):

It is the minimum cross-car distance between the trimmed doors within the measurement zone. The measurement zone lies between the beltline and 254 mm above SgRP, in the X-plane through SgRP.

Elbow room (W31): cross-car width at armrest: 

When turning, one arm will be forced to move closer to the driver’s body. It is important to ensure that the seat does not interfere with that motion. If the driver is forced to keep his arms in a wing-like posture to avoid the seat or jam their elbow into their rib cage, it will be uncomfortable. It is the cross-car distance between the trimmed doors, measured in the X-plane through the SgRP, at a height of 30 mm above the highest point on the flat surface of the armrest. If no armrest is provided, it is measured at 180 mm above the SgRP. 

Hip room(W5): minimum cross-car width at SgRP zone: 

It is the minimum cross-car  distance between the trimmed doors within the measurement zone. The measurement zone extends 25 mm below and 76 mm above SgRP, and 76 mm fore and aft of the SgRP.

Knee clearance (L62; minimum knee clearance—front): 

It is the minimum distance between the right leg K-point (knee pivot point) and the nearest interference, minus 51 mm (to account for the knee point to front of the knee distance) measured in the side view, on the same Y-plane as the K-point, with the heel of shoe at FRP (floor reference point).

Thigh Room (H13; steering wheel to thigh line): 

It is the minimum distance from the bottom of the steering wheel rim to the thigh line.

Lateral Space: 
Lateral space is the space pertaining to the side of driver/passenger. Lateral space is important for physical or psychological comfort. Conventionally, 95th percentile bi-deltoid breadth of the population with an additional allowance of 10% on each side can be considered adequate for lateral clearance during normal sitting side by side.

Seat cushion length: 

The seat cushion length should not be longer than the driver’s buttock-to-popliteal (back of knee) distance. Thus, if this length is restricted to the fifth percentile female buttock-to-popliteal distance (about 440 mm), then most drivers can use the seat and still use the back rest. Drivers with longer upper legs would prefer longer seat cushion lengths, but shorter females will not be able to use the seatback without a pillow on the seatback. Further, in case of longer seat cushion lengths, shorter females will find operation of the pedals difficult as they will be compressing the seat cushions with their thighs while depressing the pedals. Thus, an adjustable cushion length will reduce such problems and accommodate a larger percentage of the drivers. 

Seat cushion angle: 

The seat cushion should slope backward by about 5–15°. This will allow the user to slide back and allow the transferring of torso weight on to the seatback. Provision of an adjustable seat cushion angle will allow the user to find his or her preferred seat cushion angle. 

Seat width: Since females have larger hip widths (breadths), the seat cushion width should be greater than 95th percentile female sitting hip width (about 432 mm; see measurement no. 25 in Table Static Body Dimensions of United States Adults (Values Are in Millimetres) at the end). In addition, clearance should be provided for clothing (especially thick winter coats); thus, a width of 500–525 mm at the hips can be recommended.

Seatback angle: 

The seatback angle (called A40 in SAE J1100) in automotive seating is defined by the angle of the torso line (back line) of the SAE H-point machine or the two-dimensional (manikin) template (refer to SAE standards J826 and J4002 [SAE 2009]) with respect to the vertical. The seatback angle (seat recline angle) should allow drivers to assume their preferred back angles. For passenger cars, drivers generally prefer to set the seatback angle between about 20° and 26°. In trucks, due to the higher seat height (H30), drivers prefer to sit more erect with seatback angles between about 12° and 18°. 

Seatback height: From an anthropometric accommodation view point, the maximum seatback height can be selected as the fifth percentile female acromial height, which is about 509 mm above the seat surface. However, considering the Federal Motor Vehicle Safety requirements on head restraints, the seatback height is dictated by the headrest design.

Control Positions

Vehicle controls should be within a comfortable reach of the driver (and co-driver if applicable) and be comfortable to operate. Controls that are awkward to reach or difficult to operate will distract the driver/co-driver and potentially result in more driving mistakes.

Steering Wheel

The four most important aspects of the steering wheel are:

1. Distance from the driver – The steering wheel is a tool of leverage. As such, if the steering wheel is too close or too far away from the driver, they will find the steering awkward and tiring. As shown in diagram below, with their arm straight (but not straining), the driver should be able to rest their wrist on the top of the steering wheel.

   

   Distance from driver to steering wheel. A general rule of thumb is that the driver’s wrist should sit on the top of the steering wheel with their arm straight and not reaching (Not extending their shoulder forward)

   Doing so will ensure that in the worst case, the driver’s arms will not be locked straight while steering (Which is both uncomfortable and a poor leverage position).                                                                                     
2. Steering Wheel Angle – The angle of the steering wheel goes hand in hand. The arc through which the steering wheel turns determines where the hands arms, and elbows will be located. To extreme an angle, horizontally or vertically will be uncomfortable.                                                                                               
3. Steering Wheel Size – Steering wheel size determines the amount of leverage but also the amount of motion required by the driver to turn the vehicle. The scrub radius of the steering tires/wheels, the steering rack ratio and the diameter of the steering wheel all contribute to the amount of movement and effort required to steer.

Pedals The pedals, like the steering wheel involve leverage within a limited space. The three most important factors affecting the pedals are:

i. Distance from the driver – Due to the limited motion of the legs, the pedals must be  located at a proper distance from the driver to ensure they can be engaged without awkwardly stretching or pushing from cramped starting position. The comfort of the position is gauged by the driver, but generally speaking, a starting, unengaged angle for the legs should be no less than 90 degrees to ensure adequate leverage for long pedal travels. For shorter pedal travels or more laid back seating positions, angles of 120 degrees or more may be preferable. 

                                                                           

ii. Leverage Ratio – Like a typical lever, the travel of the pedal that results from its leverage ratio must be taken into account when designing the pedals and the pedal distance from the driver. Too long a travel and the motion may become fatiguing. Too short a pedal travel and the extra force needed may become fatiguing.                                                                                                                                                                              

iii. Control Sensitivity – Pedal travel again comes into play when we speak about sensitivity. The pedal travel must be tuned to the precision required for optimal control. For instance, a very short travel gas pedal might be difficult to control precisely on a bumpy surface. A short travel clutch pedal may make the clutch too quick to “bite” and cause bogging.

Information/Gauges/Communications

In addition to the road the driver sees and feels through the seat, pedals and steering wheel, there is often a need for information that helps the driver to optimize their driving style and actions.

The information needed must address the nature of the vehicle and racing (if applicable). For example, a fuel flow gauge would be useful in racing that relies heavily upon managing fuel consumption. If a driver and co-driver or pit crew need to communicate, then a communication system would be in order. If switches are needed to control aspects of the vehicle, they will need to be considered in the driver information system design.

Road or High-Performance Street machines have similar needs to racing cars, but the focus of information is generally on ensuring “Nominal” operation—that is, you’re not running out of fuel, your engine cooling system is working, you’re shifting at the right RPM, etc. 

1. Gauges –The most critical and frequently viewed gauges in a race or high-performance vehicle should be placed in or very near to the driver’s line of sight.

   

   The driver’s line of sight includes an angle range where their vision is capable of quick gauge assessment which limits the duration away from focusing on driving

   Within a 5-10° range of the line of sight, as shown in diagram IGC1 below, the driver can quickly see the gauge readouts while still keeping their eyes on the road.                 
2. Radios in Racing – Driver-to-co-driver communications should use high quality noise cancellation radio systems as the communication needs to be very clear in a co-operative racing situation like Rally. In Driver-to-Pit communications, the same principle applies, but incorporates a longer range transmission.
   
   Radio type and antenna placement should be a design consideration, especially if the race course is over undulating terrain (outside of line-of-sight transmission). As the quality of the equipment will largely dictate the range and quality of the transmission, high quality noise cancellation radios are a must.                                                                         
3. LCD displays/Data Acquisition – Steering wheel-based LCD/LED displays with data acquisition have become very popular as a single screen alternative to having multiple gauges.Considerations for a designer using one of these displays should be for its brightness and anti-reflective properties. In direct sunlight a poorly lit display will wash-out. Consideration should also be given to the flexibility of the data acquisition for your sensor requirements and its ability to customize the display.

Visibility

Seating Position/Field of View

A key input to the interface is the driver’s vision and that of any co-driver (i.e. Rally). The field of view, as shown in diagrams SP1 and SP2 below, should include visibility ahead and to the sides of the vehicle (Approximately 180 degree arc–more is even better) and visibility of the road surface.

The driver needs a sufficient level of information about the nature of the oncoming road surface and what is occurring beside them through peripheral vision to drive confidently. If the driver must strain their neck to see enough to feel confident, their field of view is inadequate.

Forward and side field of view should be at least 180 degrees. Even more is useful as the driver can turn their head slightly to pickup competitors in their peripheral vision

Vertical field of view should permit the driver to see the road surface ahead with enough detail to gauge its condition. If the surface visible is too far away, resolution is lost and road condition can become vague.

The position the driver will sit in takes into account their field of view first and foremost. However, additional factors such as control positions, comfort and leg/arm leverage must also be factored in. 

Visual Field and Visual Obstruction: 

Limits of Visual Field: Driver can turn both eyes and head to gain a wider field of view, and moreover can make use of peripheral vision to see objects or movements even without turning eyes. In the horizontal plane, the binocular field of view extends some 120 degrees, as in figure given below. Vision is sharp only over a fairly small area directly ahead. So, eyes need to be turned to focus on objects outside the foveal area. According to SAE J985 eyes generally only turn by about 30 degrees before the head is turned, which can comfortably give a further 45 degrees view to either side.

In the vertical plane eye movement is comfortable within 15 degrees above or below the horizontal, although the eye can see upto 45 degrees upward or 65 degrees downward if necessary. 

On the other hand, head can easily incline 30 degrees upward or downward. Thus, by movement of head and eye, the driver can have extended direct field view. The driver has to concentrate on direct view, that is on road. So glancing away from the road for a short period is possible. Mirror and other instruments should be close to the driver, so that driver does not require a much head and eye turn to have a look.

 

Driver’s Eye Location: 
Variation of eye positions inside the vehicle for any driving population is considerable due to variation of seat locations and variable anthropometry of the drivers. In order to address this problem, the SAE J941 ‘Eyellipse’ concept was developed as a drafting tool to define the range of eye positions within the driving population. It is based on the position of eyes of drivers in space. The distribution of eye position in space closely approximated an ellipsoid. 

During automobile design, care should be taken to provide maximum view all around either through direct vision or with the help of devices like mirror or camera. It is also important to ensure minimum visual obstruction either by vehicle components or by driver’s own body parts. This is particularly important for allowing unobstructed view of the displays on the dash board. 

Internal and External View from Driver Seat: The vision is a crucial factor in the driving task as most of the information received by the driver come through the visual sense. The clear view of road (front and rear) enables the driver a safe driving. Poor visibility conditions are stressful for the drivers and results in a significantly increased risk of accident.

Visual Needs:
The view ahead through the wind shield has to be sufficient and clear for the driver. It enables driver to stop in emergency and necessary conditions. Similarly, rear and side views are important for maintaining speed, taking turn, exerting break or during parking. On the road driver need much longer view to anticipate and prepare for avoiding actions. Views close to the vehicle is equally important when turning left or right and maintain proper distance to avoid accidents. Fig. 16 shows the view inside the vehicle, forward and side views through glasses and rear view through mirror.

Specifying the Field of View: 
Direct View: 
The views observed by the driver directly through eyes are considered as direct views. The visual field of human eye is complex, limited by anatomical and optical factors. However, it can be represented by sightlines drawn from the eye to all the points which can be seen, collectively defining the visible field of view. The view of driver can be represented in two dimensional geometry by considering a imaginary sight line (Horizon) passing through the driver’s eye. The viewing angle above the horizon can be considered for traffic signals and signs. 

The downwards view can be considered for road. Height of the dashboard and curvature of the bonnet are the two determining factor for downward view through front windshield. Upper edge of the dashboard should be at least 15 degree below that horizontal eye line of driver with smallest (5th percentile) sitting eye height. The far distance view is based on the horizon, the sightline passing through the driver’s eye.

Indirect View: The views to the rear of the vehicle mainly obtained through the mirrors. This view provides information on passing vehicle, vehicle close to the rear when the driver proposing to change the lane. The reflected view of mirror can be represented in the same way as in direct view with the viewing angles. The view of image is bounded by the frame of mirror. The image boundaries can be determined by the mirror dimensions, locations of the mirror with respect to driver’s eye and optical characteristic of mirror. By adjusting the mirror the field of view of rear can be adjusted.

The views to the rear of the vehicle mainly obtained through the mirrors. This view provides information on passing vehicle, vehicle close to the rear when the driver proposing to change the lane. The reflected view of mirror can be represented in the same way as in direct view with the viewing angles. The view of image is bounded by the frame of mirror. The image boundaries can be determined by the mirror dimensions, locations of the mirror with respect to driver’s eye and optical characteristic of mirror. By adjusting the mirror the field of view of rear can be adjusted.

Man-Machine system

A person-machine system is a system in which human and mechanical components operate together to accomplish a task. Neither part is of value without the other. A person using computer to type a document is a person machine system. A person driving a car is a more complex person-machine system,since the driver have to operate several tools together. For example, while driving a car this person has to monitor the road and at the same time using brake, gas and gear to control speed of his car.In all person-machine systems, the human operator (as example above is the driver) receives input on the status of the machine from the displays. Base on this information, the driver regulates the car by using controls to initiate some action. Suppose we are driving a car at a constant speed. We will receive input from a speedometer, we process this information mentally, and decide that we are driving too fast or too slow. We control speed of the car by easing our foot off the accelerator, that will send information to the fuel injection system to reduce the flow of gasoline to the engine, which will slow the speed of the car.This decreasing speed will be displayed on the speedometer for our information, and so the process continues.Drivers also receive information from the external environment, such as a sign noting a change in the speed limit or a child suddenly crossing a road. We process this information and in a split-second we have to make quick decision to dictate a change in speed to the machine. The drivers then will push the brake to decelerate the car or to make the car stop immediately. Person-machine systems vary in the extent to which the human operator is actively and continuously involved in the system. In person driving a car, human driver is continuously involve in operating the car and actively in the process of drivinga car. A driver need more focus and concentration while driving. A fatigue and restless driver can cause accident. This is reason that human factor inside a car need special attention. Although human factor considered as a main factors when accident happens, that will make car manufacturers are responsible to consider human factors in designing car to minimize fatigue and injury to a person with purpose to minimize accidents.

Driver Attention

Distraction: shift of attention away from the driving task for a compelling reason. 

Internal Distraction

• event in car 
• adjust radio or tape player 
• adjust window, vent, heater or similar control 
• conversation with passenger
• Navigation system destination entry
• Map and other complex visual displays
• In-vehicle office tasks (e-mail, Internet)
• In-vehicle entertainment (travelogue, CD, TV)
• Warnings
• HUD’s
• Wireless communication (cell phones)

Ingress/Egress

The ease of getting in and out of a vehicle (or ingress/egress) is one of the most important ergonomic issues for automotive manufacturers. It represents the first physical contact of a customer with a vehicle. Ingress/egress, also known as Sliding Entry, involves simulating an occupants movements while entering (ingress) and exiting (egress) a vehicle. Seat cushion height (ground to seat) is an important factor. Additionally, the greater the distance between the seat cushion and the roof line, the more comfortable the ingress/egress.

Vehicle Dimensions Relevant for Entry and Exit 

• Vertical height of the SgRP from the ground (H5)
• Lateral distance of the SgRP from outside edge of the rocker (W)
• Lateral distance of the outside of seat cushion to outside of rocker (S)
• Lateral overlap thickness of lower door (T)
• Vertical top of rocker to the ground (G)
• Vertical top of the floor to the top of the rocker (D)
• Curb clearance of doors at design weight (C)

Other Factors in Entry-Exit

1. Angle from Vertical of Door Hinge Centerline

• Top of centerline should be inward and forward
• Improves head and shoulder clearance to upper front corner of opened door

2. Door fully-opened angles

• Normally 65-70 degrees for front doors and 70-80 degrees for rear doors
• Too large of an opened angle increases difficulty of reaching door to close it

Interior Features and Conveniences

• Cabin Climate Control

• Park Assist Camera

• Head-Up Display

• Auto-Dimming Rear View Mirror

• Electric locking system

• Infotainment

• Seat control...etc

Dust and Fume prevention

The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes. The first automaker to include a disposable filter to clean the ventilation system was the Nash Motors "Weather Eye", introduced in 1940. It is recommended to change the cabin air filter annually or every 12,000 miles.

Noise and vibration in automobiles

Interior noise

Prominence acceptance criterion of any vehicle in terms of comfort at the interior part is an interior noise. It is generated due to contribution from each vehicle component, panel acoustic leakage, panel vibration, gear shifting and steering wheel vibrations. 

Noise control techniques

Sound Absorption: It is done by using porous material which act as ‘noise sponge’. Whatever noise generated is converted into heat within the sponge. Commonly used sound absorber materials are open cell foam and fiber glass. That’s the logic behind use of sponge in seat of automobiles. 

Sound Insulation: Noise transmission is prevent by using introducing of a mass barrier. Commonly used materials are thick glasses, metal.

vibration isolation: It prevent the transmission of vibration from source to receiver by introducing a flexible element in its path. Commonly used vibration isolators are spring, rubber mount, cork, etc. 

Vibration Damping:It is applicable for large vibrating surfaces. Damping mechanism works by extracting the vibration energy from the thin sheet and dissipating it as heat.