Comparative Evaluation for Pedestrian Safety Systems
Mukesh Chaudhari
E-mail : Mukesh9803@gmail.com
As a result, the congestion on roads has increased
beyond capacity leading to delay, fuel loss, accidents
and environmental pollution. Safety of operation is an
area of concern in all modes of transport including walk
mode. Though the accident rate is coming down, the
number of fatalities is still high.
Abstract – Pedestrian injuries, fatalities, and accessibility
continue to be a serious concern in India and also across
the world. There are major two systems used to protect the
pedestrian from injury or death. Collisions between
pedestrians and road vehicles present a major challenge
for public health and traffic safety professionals.
Pedestrian safety is a complicated problem due to the
many variables that comprise the built environment and
the complexity of understanding behavioral decisionmaking and outcomes. This literature review explores
recent research on the roles of human factors and
environmental factors in vehicle-pedestrian crashes,
including a brief summary of recent sources that address
countermeasures to improve the safety of the physical
environment for pedestrians. Adult skull and face injuries
in car pedestrian accidents is account for 60 percent of all
pedestrian serious injuries, whereas 18 percent of skull
injuries were due to the structure of bonnet. The above
values show the essential to think more carefully the role of
the bonnet in pedestrian skull safety. In 2010, 4,280
pedestrians were killed and an estimated 70,000 were
injured in traffic crashes in the United States. On average,
a pedestrian was killed every two hours and injured every
eight minutes in traffic crashes. Pedestrians are the main
fatality of fatal accidents. Nearly 90 percent of the total
fatalities in our country occur on rural roads while only 10
percent occur on urban roads. Conventional planning is
greatly biased to the motorized modes of transport, even
though every road users is a pedestrian at some stage of
journey. The problem is realized but efforts are negligent;
therefore, authors suggest the need to address it within an
integrated system of roads, road users and vehicles. As
automobile transportation continues to increase around
the world, bicyclists, pedestrians, and motorcyclists, also
known as Vulnerable Road Users (VRU), will become
more susceptible to traffic crashes, especially in countries
where traffic laws are poorly enforced.
As automobile transportation continues to boost
around the world, bicyclists, pedestrians, and
motorcyclists, also known as Vulnerable Road Users
(VRUs), will become more at risk to traffic crashes,
especially in countries where traffic laws are poorly
enforced. In particular, nations such as India and China,
which have growing populations as well as a growing
middle class, will see a substantial increase in traffic
injuries and fatalities if strategies are not found to ensure
the safety of Vulnerable Road Users. Many countries,
however, are employing innovative strategies to ensure
that road users can more safely navigate the urban
landscape. While bicyclists and motorcyclists are
important road users, this paper will focus on pedestrian
crash problems and solutions. Pedestrians are most at
risk in urban areas due in part to the large amount of
pedestrian and vehicle activity in urban areas. No matter
if the primary mode of transportation is the automobile,
bicycle, or public transportation; people must walk as a
part of the trip, such as from their home to the store or
place of employment, and/or to the transportation stop.
Keywords – bonnet, head injury, optimal design, Pedestrian
safety
I.
INTRODUCTION
A large proportion of the vehicular population
enlargement in the country has taken place in the towns
and cities. As towns and cities expand the outing lengths
increase. Provision of public transport services has not
matched the demand, culminating in large number of
personalized modes on road. The supply of road
infrastructure has also fallen short of the requirements.
Fig.1: Distribution of Road Traffic Fatalities by Road
User Group [2]
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With this in mind, designing safe, accessible, and
comprehensive facilities for pedestrians is vital to
reducing pedestrian crashes. Beginning with pedestrian
safety statistics at the global, regional, and national
levels, this paper will address potential countermeasures
and strategies for improving pedestrian safety from an
international perspective.
have been developed to protect pedestrians against the
effects of automotive accidents. The first approach is
active protection, which involves sensors placed in
automobiles to detect oncoming pedestrians and
potential accidents, and it subsequently offers solutions
to avoid accidents [4]. Although this approach can be
solved efficiently and offers an efficient means of
responding to safety problems, the sensor system which
must be installed in the car is more expensive and
required more care. Also the sensor system is activated
when the vehicles crashes to any other objects, beams,
dividers, etc The second approach is passive protection,
in which design measures are implemented either to
protect pedestrians from injury or to minimize the
severity of potential injury [4]. For instance, passenger
cars can be equipped with advanced devices such as
external air bags and lifting-bonnet systems [10–12],
which reduce pedestrian injuries in the event of
accidents. All solutions are continuously developing
because each solution highlights the role of automobile
owners for protecting pedestrians. There are mainly two
systems to protect the pedestrian from collision with
vehicle, one is pop-up hood system and second is to
optimize the bonnet thickness for pedestrian safety.
As expected, more crowded countries will have
higher total numbers of pedestrian deaths with China,
India, and the Russian Federation in first, second, and
third in that category, respectively.
Fig. 2: Number of Pedestrian Deaths by Country [3.0]
II. POP-UP ENGINE HOOD SYSTEM
A Research on adult pedestrian protection currently
is focusing mainly on passenger cars and commercial
vehicles. However, impacts with heavy goods vehicles
and buses are also important, especially in urban areas
and in developing countries. Pedestrian safety is the
important issues across the world. Transportation
network is a heart of a nation and transport services are
considered as growth engine of economy. Thousands of
pedestrians are killed or badly injured in automotive
accidents annually. According to the National Highway
Traffic Safety Administration (NHTSA), In 2010,
32,885 people died in motor vehicle traffic crashes in
the United States—the lowest number of fatalities since
1949 (30,246 fatalities in 1949) This was a 2.9-percent
decline in the number of people killed, from 33,883 in
2009, according to NHTSA‘s 2010 Fatality Analysis
Reporting System (FARS). In 2010, an estimated 2.24
million people were injured in motor vehicle traffic
crashes, compared to 2.22 million in 2009 according to
NHTSA‘s National Automotive Sampling System
(NASS) General Estimates System (GES). This slight
increase (1.0% increase) in the estimated number of
people injured is not statistically significant from the
number of people injured in crashes in 2009 [1].
This section describes the basic structure and
mechanisms of the pop-up engine hood system. As
illustrated in Fig. 2, the system consists of the following
three basic components.
Fig.3 : Pop-up hood system. [5]
(1) Sensors: Detect a collision between the vehicle and
a pedestrian.
The above values show the need to consider
carefully the bonnet of the passenger car to ensure
pedestrian safety. As traffic safety emphasizes
pedestrian protection, ‗pedestrian safety systems‘ were
designed to protect pedestrians. Two main approaches
Fig. 4 : Sensing system. [6]
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(2) Control unit: Judge the necessity of raising the
hood.
closes by rotating upward or downward centered on the
hood hinges (Fig. 6 (a) and (b)). In contrast, when the
pop-up system is deployed, the rear of the hood is raised
centered on the hood lock at the front of the vehicle
(Fig. 6 (c)).
(3) Actuators: Raise the rear of the hood.
The function of each component is explained in
detail below.
The hood hinge adopted is a link type hinge, as
shown in Figure 5. The link hinge is composed of an
upper bracket, lower bracket, arm A, arm B, three
pivots, and a pin. According to an ignition signal from
the ECU, gas from the micro gas generator raises the
shaft. The shaft shears the hood hinge pin, lifting the
rear portion of the hood approximately 100mm, thereby
providing a space between the hood and the hard
components under the hood, such as the engine.
Sensors - Three sensors for detecting a collision with a
pedestrian are installed behind the front bumper fascia
as shown in Fig. 3. This structure was adopted because
the front bumper is usually the first part to come in
contact with a pedestrian's body in a collision with a
vehicle. The sensors are positioned on the right and left
sides and in the center. The sensors function to detect a
change in acceleration and have experience of use as the
airbag sensors. These devices detect the movement of
the bumper fascia caused by contact with a pedestrian's
legs.
Before operation
after operation
Fig. 7. Hood hinge of link type. [7]
Fig. 5. Sensor for pedestrian detection. [5]
Actuators - The actuators that provide the driving force
for raising the rear of the hood are constructed with an
extendable cylinder operated by pyrotechnics. As shown
in Fig. 5, the length of the three-stage cylinder before
operation is less than one-half of its extended size.
Fig. 8. Operation of hinge and actuator.[8]
A detailed diagram of the hood hinge mechanism is
shown in Fig. 7. During normal opening or closing of
the hood, the lock lever fixes link (a) and link (b),
allowing only link (a) to rotate. When the pop-up hood
system is deployed, the actuator head presses on the
lock lever, allowing link (b) to rotate. The actuator
cylinder extends to raise the rear of the hood, with the
hood lock serving as the fulcrum of the hood's upward
rotation. As a result of these operations, the rear of the
hood is raised by approximately 100 mm to secure
buffer space between the hood and the high-stiffness
parts beneath it.
Fig. 6. Actuator. [5]
Figure 6 shows the relationship between the
operation of the actuators and the hood hinges for
opening/closing the hood. Normally, the hood opens or
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deployment time from the moment of the impactor
contact with the front bumper.
Fig. 9. Pop-up mechanism of hood hinge. [9]
Collapsible Mechanism of Actuators:This section presents an example of numerical
simulations [5], [6] that were conducted to validate the
effectiveness of the collapsible mechanism of the
actuators. These simulations were performed with the
PAM-CRASH.
Fig. 10. Example of displacement history of pop-up. [8]
Method of Evaluating Head Protection Performance
The headform impactor was projected against the
hood and other areas of the vehicle front-end to
investigate head protection performance, which was
evaluated using the head injury criterion (HIC) as
defined in Eq. (1) below.
Software using a headform impactor. Figure 8
shows acceleration histories of the headform impactor
when it struck the hood surface near one of the
actuators. The impactor acceleration is indicated along
the vertical axis in relation to its displacement along the
horizontal axis. The solid line is for a pop-up hood
system with collapsible actuators and the dashed line is
for a system with rigid actuators. The waveform for the
system without the collapsible mechanism indicates that,
following the initial peak for the primary impact with
the hood surface, the secondary impact with the actuator
produced a relatively large acceleration peak. In
contrast, the waveform for the system with the
collapsible mechanism indicates that the actuators
initially supported the rear of the hood until the preset
load was reached, after which the collapsible
mechanism worked to avoid another increase in
impactor acceleration. As a result, the system with the
collapsible mechanism kept the subsequent impactor
acceleration below that of the level of the primary
impact with the hood, thereby verifying the
effectiveness of this mechanism.
With the condition
Where A is the acceleration of the headform impactor
and t1 and t2 are the initial and final times. In order to
reduce the HIC, the mean acceleration should be low
and there should not be any pronounced acceleration
peak.
III REDESIGNING THE BONNET FOR
PEDESTRIAN SAFETY
Redesigning the structure of the bonnet to improve
pedestrian protection has recently received considerable
attention by automobile manufacturers and industry,
institutes. Figure 11 illustrates a method of protecting
pedestrians by creating more holes in the ribs of
reinforcement to reduce the bonnet stiffness [11].
Previous research on improving pedestrian safety also
increased the number of ribs to create a bonnet surface
with more uniform stiffness [13]. Figure 12 shows the
reinforcement structure developed to protect pedestrians
in accidents. Currently, some automobiles use a multicone structure (Fig. 12) instead of a rib structure for
bonnet reinforcement.
Validation of System Deployment Completion Time –
In order to validate that the pop-up engine hood
system could be deployed before the targeted system
deployment completion time explained in the preceding
section, tests were conducted with impactors that
simulated the mass of pedestrians. Figure 10 shows an
example of the displacement history of the pop-up hood,
where the amount of hood displacement near the
actuators is shown along the vertical axis in relation to
elapsed time along the horizontal axis. The results
indicate that the hood was raised the specified amount
with sufficient time to spare in relation to the targeted
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It is very important to select the most helpful
thicknesses of the bonnet skin and bonnet reinforcement
for each bonnet structure. Kalliske and Friesen [14]
reduced the bonnet stiffness and mass by reducing the
bonnet skin thickness to protect the pedestrian head.
However, this research did not expose the basis for
selecting the bonnet skin thickness. This research has
simply reduced the bonnet skin thickness rather than
seeking a basis for optimizing the values. Moreover, the
bonnet stiffness must be systematically optimized
because some components within the engine
compartment can often be very close to the bonnet
surface and these components can damage the skull of
human head when collision occurs.
Fig. 12 The solution of an alternative design for
protection of the pedestrian head [13]: (a) traditional
design; (b) increased number of ribs; (c) multi-cone
design
This study analyses the effects of the bonnet skin
and bonnet reinforcement thickness on pedestrian head
injury by performing number of simulation of head form
impactor to bonnet top test as per European Enhanced
Vehicle-safety Committee (EEVC) Working Group 17
(WG17) regulations using different thicknesses. Many
points on the bonnet surface will be considered to
enhance pedestrian friendliness by using this method. A
bonnet with the optimal thicknesses not only is
pedestrian friendly but also is as stiff as possible. Based
on the proposed method, this study presents steps for
optimizing the bonnet skin and bonnet reinforcement
thicknesses for a particular automobile model.
Fig. 11 Pedestrian protection by the modified original
reinforcement structure [11]
If the bonnet has poor stiffness, there is a risk that
components within the engine compartment may strike
the bonnet during collision, increasing the danger to the
pedestrian and negating the benefits of the reduced
stiffness. Therefore, bonnet redesign not only must
simply reduce the bonnet stiffness and mass but also
should consider the bonnet deflection during collision.
Presently there are two methods for evaluating
pedestrian injury. The first method uses pedestrian
impactors to evaluate corresponding areas on the
vehicle. The second method uses a complete dummy to
evaluate the vehicle‘s frontal structure. Both the
complete dummy and the pedestrian impactor methods
require complicated physical testing systems.
Furthermore, the pedestrian impactors must pass a series
of tests to obtain certification. Testing the material
properties of pedestrian impactors is time consuming.
Numerical simulation offers another reliable method of
solving the above problems. One advantage of this
method is its ability to solve optimization problems.
While mathematical analysis is not an easy method of
solving optimization problems, analysis of simulation
results is relatively simple and effective. Because of the
above advantages, all pedestrian-head-to-bonnet-top
tests in this study will be performed using numerical
simulation.
1
SIMULATION
OF
BONNET TESTS
PEDESTRIAN-HEAD-TO
1.1 Pedestrian-head-to-bonnet tests
The European Commission also published a directive
to assess the level of pedestrian protection for vehicle
fronts in 2003. The European Parliament supported the
commitment on pedestrian safety proposed by the
European Automobile Manufacturers‘ Association, and
thus pedestrian protection measures have been required
on all passenger cars sold in Europe since 2005 [15].
The EEVC WG17 established a series of component
tests based on the three most important areas of injury:
head, upper leg, and lower leg. The EEVC WG17
developed this method for assessing the pedestrian
friendliness of a vehicle. The EEVC WG17 tests consist
of four models of pedestrian impactor models, namely
child headform, adult headform, upper-legform and
lower-legform impactors. Figure 13 illustrates the
pedestrian protection concept proposed by the EEVC
WG17 [16].
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Fig. 15. Determination of WAD [16]
1.2 Finite element model and simulation
Fig. 13 Pedestrian protection concept proposed by the
EEVC WG17 [16]
In Finite element the model of vehicle and adult
headform is crated. This study analyses the effect of the
bonnet skin and bonnet reinforcement thicknesses on
pedestrian head injury by performing headform
impactor simulations of the EEVC WG17 regulations
using different thicknesses. Figure 16(b) shows the
finite element models of adult headform impactors.
These EEVC WG17 regulations thus will be
completed and applied to vehicle manufacturing in
Europe. In India there is no such regulation for vehicle
manufacturing. The adult headform impactor is used to
test the points lying on boundaries described by a WAD
of 1500mm and the rear of the bonnet top, or a WAD of
2100mm for a long bonnet. Each section is divided into
three parts, as illustrated in Fig.14.
Fig. 16.The finite element model used in pedestrian –
head – bonnet impact simulations: (a) the passenger car
model [18]; (b) the headform impactor model [17]
Fig. 14 Description of the impact area for pedestrian
headform- impactor-to-bonnet-top tests
The vinyl skin is modelled using viscoelastic
material, and a steel core with elastic material [17]. All
headform impactor parts use solid elements. The adult
headform impactor model consists of 3713 nodes and 13
783 solid elements. The adult headform impactors
satisfy the EEVC WG17 certification tests [17],
demonstrating the feasibility of their use in simulating
headform impactor tests. Bonnet-top simulations are
performed using the adult headform impactors
simulations of the headform-to-bonnet-top test are
performed using the finite element models of the
headform impactor mentioned above and a Ford Taurus
car model [18], as shown in Fig. 16 (a). In the engine
compartment, components that are close to the bonnet
top include the oil cap and the battery. This study does
not consider the effect of the engine compartment
arrangement on the head injury criterion (HIC) value.
Therefore, all parts in the engine compartment that are
close to the bonnet are moved down to ensure that the
bonnet does not impact any parts in the engine
compartment during simulation.
In each part, a minimum of three tests is carryout at
spots with high injury risk. Test points should vary
according to the types of structure, which vary
throughout the assessment area. The selected test points
for the adult headform impactor should be a minimum
of 165mm apart, a minimum of 82.5mm inside the
defined bonnet side reference lines, and a minimum of
82.5mm forwards of the defined bonnet rear reference
line. The impact angle for tests with the adult headform
impactors must be 650 with respect to the ground
reference level. The initial impact velocity is 40 km/h
for the adult headform impactors. Distances (WADs)
(Fig. 15) of 1000mm and rear reference line. Each
selected test point for the child headform impactor
should also be a minimum of 130mm rearwards of the
bonnet leading-edge reference line. The impact angle for
tests with the adult headform impactors must be 65 0
respectively with respect to the ground reference level.
The initial impact velocity is 40 km/h for and the adult
headform impactors.
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[9]
Ishikawa, H., et al.: ―Computer Simulation of
impact Response of the Human Body in Car
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[10]
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SPIE, vol. 4763, 2003, pp. 106–112 (SPIE,
Bellingham, Washington).
[11]
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[12]
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[13]
C. K. Simms, ―Developments in crash safety: a
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[14]
I.Kalliske, and F.Friesen, ―Improvements to
pedestrian protection as exemplified on a
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(ESV), Amsterdam, The Netherlands, 4–7 June
2001, paper 283, 10 pp. (National Highway Traffic
Safety Administration, Washington, DC
[15]
Directive 2003/102/EC of the European Parliament
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Luxembourg).
[16]
Improved test methods to evaluate pedestrian
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[17]
Kaoru
Nagatomi,
Kaoru
Nagatomi‖DEVELOPMENT AND FULL-SCALE
DUMMY TESTS OF A POP-UP HOOD SYSTEM
FOR PEDESTRIAN PROTECTION‖, Paper
number 05-0113
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Nuneaton,
Warwickshire, UK, 2001.
IV. CONCLUSIONS
Both the methods give the optimal results to protect
the pedestrian safety. In both the methods the
Hypermesh and Ls-Dyna software are used. To protect
the pedestrian these systems must be implemented to all
the manufactures of automobile vehicles. This study
analyses and proposes a method of identifying the most
effective values for the bonnet reinforcement thickness
and the bonnet skin thicknesses to protect pedestrians
while maximizing the bonnet stiffness. The method
presented in this study uses the regression technique to
design constraints for the optimization problem. The
proposed algorithm identifies numerous critical
positions on the bonnet surface with respect to
pedestrian safety. The algorithm used to optimize the
thicknesses is solved by combining LS-DYNA and LSOPT to simulate and analyze the simulation results.
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