Pedestrian safety through vehicle design
Encyclopedia
Almost two-thirds of the 1.2 million people killed annually in road traffic crashes worldwide are pedestrian
s. Despite the magnitude of the problem, most attempts at reducing pedestrian deaths have focused solely on education and traffic regulation. However, in recent years crash engineers have begun to use design principles that have proved successful in protecting car occupants to develop vehicle design concepts that reduce the likelihood of injuries to pedestrians in the event of a car-pedestrian crash. These involve redesigning the bumper, hood (bonnet), and the windshield
and pillar
to be energy absorbing (softer) without compromising the structural integrity of the car.
Most pedestrian crashes involve a forward moving car (as opposed to buses and other vehicles with a vertical hood/bonnet). In such a crash, a standing or walking pedestrian is struck and accelerated to the speed of the car and then continues forward as the car brakes to a halt. Although the pedestrian is impacted twice, first by the car and then by the ground, most of the fatal injuries occur due to the interaction with the car. The vehicle designers usually focus their attention on understanding the car-pedestrian interaction, which is characterized by the following sequence of events: the vehicle bumper first contacts the lower limb
s of the pedestrian, the leading edge of the hood hits the upper thigh
or pelvis, and the head
and upper torso
are struck by the top surface of the hood and/or windshield.
resulting from the hard impact of the head against the stiff hood or windshield. In addition, although usually non-fatal, injuries to the lower limb (usually to the knee joint and long bones) are the most common cause of disability due to pedestrian crashes. A Frontal Protection System
(FPS) is a device fitted to the front end of a vehicle to protect both pedestrians and cyclists who are involved in a front end collision with a vehicle. Car design has been shown to have a large impact on the scope and severity of pedestrian injury in car accidents.
and Jaguar XK
feature a novel pop-up bonnet
design, which adds 6.5 cm (2.5", C6) extra clearance over the engine block if the bumper senses a hit.
and the tibia
/fibula and damage to the knee
ligaments due to bending of the joint.
Thus, attempts at reducing these injuries involve reducing the peak contact forces by making the bumper softer and increasing the contact area and by limiting the amount of knee bending by modifying the geometry of the front end of the car. Computer simulations and experiments with cadaver
s show that when cars have lower bumpers, the thigh and leg rotate together causing the knee to bend less and thus reducing the likelihood of ligament
injuries. Deeper bumper profiles and structures under the bumper (such as the air dam) can also assist in limiting the rotation of the leg.
An early example can be found on tram
s in the form of a lifeguard which prevents pedestrians from being caught between the wheels of the leading bogie should they be hit. When a pedestrian hit the lifeguard a scoop/grille would be automatically lowered in front of the vehicle.
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...
s. Despite the magnitude of the problem, most attempts at reducing pedestrian deaths have focused solely on education and traffic regulation. However, in recent years crash engineers have begun to use design principles that have proved successful in protecting car occupants to develop vehicle design concepts that reduce the likelihood of injuries to pedestrians in the event of a car-pedestrian crash. These involve redesigning the bumper, hood (bonnet), and the windshield
Windshield
The windshield or windscreen of an aircraft, car, bus, motorbike or tram is the front window. Modern windshields are generally made of laminated safety glass, a type of treated glass, which consists of two curved sheets of glass with a plastic layer laminated between them for safety, and are glued...
and pillar
Pillar (car)
Pillars are the vertical supports of the greenhouse of an automobile — known respectively as the A, B, C or D-pillar moving in profile view from the front to rear....
to be energy absorbing (softer) without compromising the structural integrity of the car.
Anatomy of a pedestrian crash
Lower limb
The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:...
s of the pedestrian, the leading edge of the hood hits the upper thigh
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
or pelvis, and the head
Human head
In human anatomy, the head is the upper portion of the human body. It supports the face and is maintained by the skull, which itself encloses the brain.-Cultural importance:...
and upper torso
Torso
Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:...
are struck by the top surface of the hood and/or windshield.
Reducing pedestrian injuries
Most pedestrian deaths occur due to the traumatic brain injuryTraumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
resulting from the hard impact of the head against the stiff hood or windshield. In addition, although usually non-fatal, injuries to the lower limb (usually to the knee joint and long bones) are the most common cause of disability due to pedestrian crashes. A Frontal Protection System
Frontal Protection System
A Frontal Protection System is a device fitted to the front end of a vehicle to protect both pedestrians and cyclists who are involved in the unfortunate event of a front end collision with a vehicle....
(FPS) is a device fitted to the front end of a vehicle to protect both pedestrians and cyclists who are involved in a front end collision with a vehicle. Car design has been shown to have a large impact on the scope and severity of pedestrian injury in car accidents.
Protecting the head
The hood of most vehicles is usually fabricated from sheet metal, which is a compliant energy absorbing structure and thus poses a comparatively small threat. Most serious head injuries occur when there is insufficient clearance between the hood and the stiff underlying engine components. A gap of approximately 10 cm is usually enough to allow the pedestrian’s head to have a controlled deceleration and a significantly reduced risk of death. Creating room under the hood is not always easy because usually there are other design constraints, such as aerodynamics and styling. In some regions of the hood it can be impossible. These include along the edges on which the hood is mounted and the cowl, where the hood meets the windshield. Engineers have attempted to overcome this problem by using deformable mounts, and by developing more ambitious solutions such as airbags that are activated during the crash and cover the stiff regions of the hood. The 2006 year model of Citroën C6Citroën C6
The Citroën C6 is an executive car produced by the French luxury marque Citroën since 2005.-Overview:Inspired by the C6 Lignage prototype which was first shown at the Geneva Motor Show in the spring of 1999, but differs from the concept car's styling in minor details...
and Jaguar XK
Jaguar XK
The Jaguar XK series is a series of grand tourer cars produced by British car maker Jaguar since 1996. The series was introduced at the Geneva Motor Show on 5 March 1996. The first generation of the series, the XK8, replaced the XJS, and was available as a coupé and convertible...
feature a novel pop-up bonnet
Hood (vehicle)
The hood or bonnet is the hinged cover over the engine of motor vehicles that allows access to the engine compartment for maintenance and repair. In British terminology, hood refers to a fabric cover over the passenger compartment of the car...
design, which adds 6.5 cm (2.5", C6) extra clearance over the engine block if the bumper senses a hit.
Protecting the limbs
Most limb injuries occur due to a direct blow from the bumper and the leading edge of the hood. This leads to contact fractures of the femurFemur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
and the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
/fibula and damage to the knee
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
ligaments due to bending of the joint.
Thus, attempts at reducing these injuries involve reducing the peak contact forces by making the bumper softer and increasing the contact area and by limiting the amount of knee bending by modifying the geometry of the front end of the car. Computer simulations and experiments with cadaver
Cadaver
A cadaver is a dead human body.Cadaver may also refer to:* Cadaver tomb, tomb featuring an effigy in the form of a decomposing body* Cadaver , a video game* cadaver A command-line WebDAV client for Unix....
s show that when cars have lower bumpers, the thigh and leg rotate together causing the knee to bend less and thus reducing the likelihood of ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
injuries. Deeper bumper profiles and structures under the bumper (such as the air dam) can also assist in limiting the rotation of the leg.
Trams
Tram
A tram is a passenger rail vehicle which runs on tracks along public urban streets and also sometimes on separate rights of way. It may also run between cities and/or towns , and/or partially grade separated even in the cities...
s in the form of a lifeguard which prevents pedestrians from being caught between the wheels of the leading bogie should they be hit. When a pedestrian hit the lifeguard a scoop/grille would be automatically lowered in front of the vehicle.
See also
- Driver visibilityDriver visibilityIn transport, driver visibility is the maximum distance at which the driver of a vehicle can see and identify prominent objects around the vehicle. Visibility is primarily determined by weather conditions and by a vehicle's design. The parts of a vehicle that influence visibility include the...
- Road safety
- Car accidentCar accidentA traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction,...
s - Motorcycle SafetyMotorcycle safetyMotorcycle safety concerns many aspects of vehicle and equipment design as well as operator skill and training that are unique to motorcycle riding.-Accident rates:...
- Tram accidentTram accidentA tram accident is generally an accident in which a tram is involved . When general traffic safety is evaluated, as in traffic accident statistics, any accident involving a tram or a tram system can be considered to be a tram accident...
Further reading
- Protecting pedestrians by vehicle design
- Used Car Safety Ratings - includes information on how seriously your vehicle is likely to harm other road users
- Assessment of Pedestrian Protection Afforded by Vehicles in Australia
- Pedestrian protection in vehicle impacts: Further results from the Australian New Car Assessment Program
- The Truth About Europe's Pedestrian Safety Legislation