Anoop Seminar Report20

8/3/2019 Anoop Seminar Report20

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1.Abstract In this paper, we propose a novel decentralized traffic light control using

wireless sensor network. The system architecture is classified into three layers; the wireless

sensor network, the localized traffic flow model policy, and the higher level coordination of

the traffic lights agents. The wireless sensors are deployed on the lanes going in and out the

intersection. These sensors detect vehicles number, speed, etc. and send their data to the

nearest Intersection Control Agent (ICA) which , determines the flow model of the

intersection depending on sensors data (e.g., number of vehicles approaching a specific

intersection). Coping with dynamic changes in the traffic volume is one of the biggest

challenges in intelligent transportation system (ITS). Our main contribution is the real-time

adaptive control of the traffic lights. Our aim is to maximize the flow of vehicles and reduce

the waiting time while maintaining fairness among the other traffic lights. Each traffic light

controlled intersection has an intersection control agent that collects information from the

sensor nodes.

An intersection control agent manages its intersection by controlling its traffic lights.

agents can exchange information among themselves to control a wider area. We envision a

smart road system were the total trip time is minimum due to minimizing the

average waiting time on traffic lights. In addition to minimizing the average traffic waiting

time, we would like to see a road system which can optimize the traffic flow by utilizing the

free roads. Tremendous amount of time and power is wasted due to a green traffic light

with no cars passing on its lane.

Many solutions were proposed to solve the traffic jam .Most conventional traffic

surveillance systems use intrusive sensors, including inductive loop detectors, micro-loop

probes, and pneumatic road tubes. However, these sensors disrupt traffic during installation

and repair, which leads to a high cost installation and maintenance. In addition, over the

ground sensors like videos, radars, and ultrasonic were used. These systems are also high

cost and their accuracy depends on environment condition [1] This paper presents a real-

time adaptive system based on wireless sensors that has the potential to establish a new era

of traffic control and surveillance because of its low cost and potential for large scale

deployment. Our system consists, mainly, of the wireless sensor network and the

intersection control agents. The wireless sensor network composed of group of nodes,

each comprising one or more sensors, a processor, a radio and a battery. They generate

traffic information such as number of cars, speed and length of the vehicles, based on

processing of the sensor data. The information is then sent to

The nearest intersection control agent over the radio. The intersection control agent collects

the information from the sensor nodes to analyse traffic conditions and take actions such

as adjusting the traffic light durations or exchanging information with other intersection

agents for better optimization of traffic flow. In the field of Multiagent Systems (MAS) [2][3],

controlling intersections is studied with intelligent system on mind. Although these systems

has the potential to revolutionize traffic surveillance they are still far from being adopted by


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intersection control agent. In section 5 discuss the simulation and we conclude in section 6.

the ITS. Using wireless sensor network along with intelligent transportation system is still in

its preliminary stage. To compete with current technologies, however, the data provided by

the system must be accurate, delivered to the traffic intersection agents within a certain

time for real-time applications, and the

lifetime of the system must be on the order of several years.We use Green Light District

(GLD) 1 simulator [4] to test our model. GLD allows us to create road maps and add our own

intersection traffic flow policy. In the next section, we briefly review some approaches that

coordinate traffic lights. Section 3 presents wireless sensor networks model. Section 4

discuses

2. RELATED WORK-

To replace the costly and high maintenance classic trafficsurveillance such as inductive

loops, Cheung et al. [1] built a traffic surveillance technology system based on wireless

sensors. Their system is deployed in freeways and at intersections for traffic measurements

such as vehicle count, occupancy, speed, and vehicle classification which cant be 1GLD is an

open-source software and can be downloaded from

{http://sourceforge.net/projects/stoplicht/} 1-4244-0667-6/07/$25.00 2007 IEEE 187

Authorized licensed use limited to: INDIAN INSTITUTE OF SCIENCE. Downloaded on June 22,

2009 at 09:33 from IEEE Xplore. Restrictions apply. obtained from standard inductive loops.

The experiments in [1] shows that deploying wireless sensor network for traffic monitoring

provides %99 of detection rate in real time. Using wireless sensor network for

transportation applications provides measurements with high spatial density and accuracy.

A network of wireless magnetic sensors [1] offers much greater flexibility and lowerinstallation and maintenance costs than loop, video or radar detector systems. Chen et al.

[5] propose a prototype of Wireless sensor network for Intelligent Transportation System

(WITS). WITS system is used for the information gathering and data transferring . In this

system three types of WITS nodes are used;

1) the vehicle unit on the individual unit,

2) the roadside unit along both sides of road, and

3) the intersection unit on the intersection.

The vehicle unit measures the vehicle parameters and transfers them to the roadside units.

The roadside unit gathers the information of the vehicles around, and transfers it to the

intersection unit. The intersection unit receives and analyzes the information from other

units, and passes them to the strategy sub-system, which in turn calculates an appropriate

scheme according to the preset optimization target (such as maximum throughput,

minimum waiting time, etc.) Mainly, the intersection unit wants to know how many vehicles

in every lane will reach the intersection before the signal phase ends. But there is no enough


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discussion about how this information helps the intersection unit. Hull et al. [6] designed a

mobile distributed sensor computing system called CarTel. A CarTel node is a mobile

embedded computer coupled to a set of sensors. Each node gathers and process sensor

readings locally before delivering them to a central portal, where the data is stored in a

database for further analysis and visualization. In general, CarTel makes it easy to collect,

process, deliver, and visualize heterogenous data from a intermittently connected mobile

nodes. In [6] CarTel is deployed on six cars for over a year to analyze commute times,

metropolitan Wi-Fi deployments, and for automative diagnostics. Although this system has

potentials for smoother commute time by collecting information about the traffic, but it

does not solve the traffic problem. That is, only vehicles with CarTel node can benefit from

this system.

3. WIRELESS SENSOR NETWORK MODEL-

In this section, we discuss the wireless sensor network model [1] we will use in our system.

A. Sensor Node hardware

The sensor nodes consist of a processor, a radio, a magnetometer, a battery and a cover for

protection from the vehicles. The microprocessor is Atmel ATmega128L with 128kB of

programmable memory and 512kB of data flash memory. It runs TinyOS, an operating

system developed at UC Berkeley, from its internal flash memory. TinyOS enables the single

processor board to run the sensor processing and the radio communication simultaneously.The radio is ChipCon CC1000 916MHz, frequency shift keying (FSK) RF transceiver, capable

of delivering up to 40kbps. The RF transmit power can be changed in software. There are

two HMC1051Z magnetic sensors, based on anisotropic magneto resistive (AMR) sensor

technology.To receive one sample, the magnetometer is active for 0.9 m sec and the energy

spent for taking one sample is 0.9J. The magnetometer is turned off between samples for

energy conservation. The battery is Tadiran Lithium TL5135, with 1.7Ah capacity in a

compact size. The entire unit is encased in a SmartStud cover, designed to be placed on

pavement and able to withstand 16,000 lbs. So the node is protected and can be glued on

anywhere on the pavement.

B. Vehicle Detection

We use magnetometer sensor for vehicle detection. The sensor detects distortions of the

Earths field caused by a large ferrous object like a vehicle. Since the distortion depends on

the ferrous material, its size and orientation, a magnetic signature is induced corresponding

to the vehicles shape and configuration. For detecting the presence of a vehicle,


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measurements of the (vertical) z-axis is a better choice as it is more localized and the signal

from vehicles on adjacent lanes can be neglected.

C. Communication protocol

Several proposals have been advanced for random access schemes to reduce the effects of

energy consuming operations such as constantly listening to the channel, overhearing

packets not destined for them, and transmissions collis ions. These proposals achieve power

savings up to a factor of 10 at the cost of considerable increase in hardware or control

complexity. The TDMA schemes on the other hand are more power efficient since they

allow the nodes in the network to enter inactive states until their allocated time slots.

However, previously proposed TDMA schemes do not take advantage of the fact that all

sensor data are destined for a single access point and introduce distributed synchronization

overhead. We adopt PEDAMACS (Power Efficient and Delay Aware Medium Access Protocol

for Sensor Networks) [1] for our traffic system. PEDAMACS is a TDMA scheme that discovers

the topology of the network and keeps the nodes synchronized to validate the execution ofa TDMA schedule. It is designed to meet both delay and energy requirements of traffic

applications by exploiting the special characteristics of sensor networks.

The data at the sensor nodes in the wireless network is periodically transferred to a

distinguished node called access point (AP) for purposes of control. The AP then transfers

the data to the traffic management center. Moreover, the sensor nodes have limited

(transmit) power and energy, but the access point is not so limited. Consequently,

communication from nodes must travel over several hops to reach the access point, but

packets from the access point can reach all nodes in a single hop. PEDAMACS protocol

operates in four phases: the topology learning phase, the topology collection phase, thescheduling phase and the adjustment phase. In the topology learning phase, each node

identifies its (local) topology information, 1-4244-0667-6/07/$25.00 2007 IEEE 188


2009 at 09:33 from IEEE Xplore. Restrictions apply. i.e. its neighbors and its interferers, and

its parent node in the routing tree rooted at the AP obtained according to some routing

metric. In the topology collection phase, each node sends this topology information to the

AP so, at the end of this phase, the AP knows the full network topology. At the beginning of

the scheduling phase, the AP broadcasts a schedule. Each node then follows the schedule: In

particular, the node sleeps when it is not scheduled either to transmit a packet or to listen

for one. The adjustment phase is included if necessary to learn the local topology

information that was not discovered in topology learning phase or that changed, depending

on the application and the number of successfully scheduled nodes in scheduling phase.

The determination of the schedule based on the topology of the network at the AP is

performed according to the PEDAMACS scheduling algorithm. The scheduling algorithm

ideally should minimize the delaythe time needed for data from all nodes to reach the

access point. However, this optimization problem is NP-complete. PEDAMACS instead uses a


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polynomial time scheduling algorithm which guarantees a delay proportional to the number

of packets in the sensornetwork to be transferred to the AP in each period. The algorithm

assigns a group of non-conflicting nodes to transmit in each time slot, in such a way that the

data packets generated at each node reaches the AP by the end of the scheduling frame.

D. Road Intersection Configuration

We use intersections controlled by four traffic lights. Each traffic light is responsible for

controlling traffic on three lanes. We assume the right lane turns right only, center lane goes

straight or left and left lane goes left only. We deploy sensor nodes on every lane (see

Figure 1. We place the sensor nodes where they can monitor the traffic before entering the

intersection and after leaving the intersection. We use the nodes placed after the

intersection to locally determine the direction of the vehicle within one intersection.

4. INTERSECTION CONTROL AGENT-

The system prototype consists of four elements; 1) the wireless sensor network (WSN), 2)

the intersection control agents (ICAs), 3) the actuators (i.e., traffic lights), and 4) the

environment (i.e., vehicles) (see Figure 2).

A. Adaptive Traffic LightControl

Figure 1 depicts our adaptive traffic light control system. Traffic lights are controlled by an

intersection control agent in the vicinity. An intersection agent coordinates four traffic lights

at a time. At each traffic lights there are three nodes with magnetometer sensors. These

sensors multi-hop to the access point its location, lane number, and number of vehicles

passed within ttime. The sensor nodes are positioned at ddistance from the traffic light toallow for enough time for the data to multi-hop to the intersection agent analyzed and then

send to the targeted traffic light.

Fig. 1. Road intersection configuration

B. Message Types


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We have created a protocol by which the agents can communicate the bare minimum of

information necessary to function appropriately. The protocol consists of several message

types for each agent, as well as some rules governing when the messages should be sent

and what sorts of guarantees accompany them.

1) Sensor Nodes to ICA: Sensor nodes count number of vehicles approaching anintersection. Every node monitors one lane. The message sent from the sensor nodes to the

intersection control agent include number of vehicles, time duration of the collected data,

and lane number.

2) IC A to Sensor Nodes: After receiving information from all the nodes monitoring a

specific intersection, the intersection agent decide the best flow model (policy) for the

vehicle flow.

3) Greedy ICA to ICA: Intersection control agent can exchange information with other

intersection control agents in its vicinity to improve the flow of vehicles in a wider area. Thisis because the agent can select a better policy depending on more information collected.

We call this situation greedy policy because each agent satisfy its intersection flow without

paying attention of other intersections flow.

4) ICA to ICA with Coordination:This is the same as the previous one except that the agents

coordinate among themselves to achieve even better flow. The intersection control depends not

only on the analysis one agent but on the coordination of multiple agents.

5. SIMULATION-

We test our model using Green Light District Simulator [4]. GLD is a Java based trafficsimulator that allows us to design arbitrary roads and intersections, monitor traffic flow

statistics and test different traffic light controllers. Using GLD has the advantage of

predicting whether a costly new system would be profitable when applied to a certain

infrastructure. 1-4244-0667-6/07/$25.00 2007 IEEE 189 Authorized licensed use limited

to: INDIAN INSTITUTE OF SCIENCE. Downloaded on June 22, 2009 at 09:33 from IEEE Xplore.

Restrictions apply.

Fig. 2. System Life Cycle


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Green Light District simulator consists of two parts; the Editorand the Simulator. The Editor

enables the user to create the an infrastructure. This includes creating the road map with its

junctions and traffic lights. Afterwards, the number of lanes on roads, drive lane rules, and

algorithms for the traffic lights and starting frequencies for road users can be set. The

Simulator can then load the road map and run the simulation based on that map. Before

starting a simulation, the user can choose which traffic light controller (TLC) and which

driving policy will be used during the simulation. In our experiments, we do not incorporate

the driving policy in our simulation results.Since GLD is an open source, it can be easily

extended in order to add new algorithms for traffic light controllers.

Definitions. Here, we will explain some terminology that we use:

Infrastructures. Figure 3 depicts a sample infrastructure. The square node in the middle is

an intersection with eight traffic lights; one traffic light for each lane. The square nodes

without traffic lights are called edge nodes. Edge nodes have certain probability of

generating generate a vehicle at each time step.

Agents. Vehicles and traffic lights are two types of agents in this simulator. Edge-node

generates a vehicle and assigns a destination , which is one of the other edge-nodes.

Controllers. Every junction is controlled by a traffic light controller (TLC). A TLC is an

algorithm that specifies the way traffic lights are set during the simulation. In addition, a TLC

can share information with other controllers to improve global performance. GLD has

several built-in TLCs, and allows forcustom TLCs.

Example. Figure shows a road map with 5 edge nodes and 8 intersections, 6 of which have

traffic lights, and 15 roads, 4 lanes wide each. At each edge node, 0.25 cars aregeneratedeach cycle. Results.Figures 4567 shows the average junction waiting time. Traffic

lights will be set to the setting that will let the most cars pass. This might not mean the best

setting, even forone junction, because junctions do not communicate, and roadusers on

linked lanes might not be able to proceed because the decision about that lane at the next

traffic light is different. Most Cars relieves the most clogged up lanes, but does not take into

account how full lanes are in comparison with others.


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Fig. 3. A screenshot from the Green Light District simulator.

Fig. 4. Average junction waiting time.

VI. CONCLUSION AND FUTURE WORK

Centralized approaches to traffic light control cannot cope with the increasing complexity of

urban traffic networks. This paper proposes a traffic control system using wireless sensor


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networks. The new decentralized system depends on the traffic information collected from

the wireless sensor network to achieve a realtime adaptive traffic control. The advantages

of information collected from the wireless sensor network has two folds:

1) improve the localized flow model in the intersection

2) improve the coordination among the neighbor traffic lights. Some deeper problems need

a further research.

For example, 1) the intersection units in the same city form a huge network, which can be

used to transfer traffic information. What challenges will we meet in a large scale of

network?

2) Vehicle unit can only transfer dynamic information of a vehicle up to now. If we write

some solid information of this vehicle, such 1-4244-0667-6/07/$25.00 2007 IEEE 190


2009 at 09:33 from IEEE Xplore. Restrictions apply.

Fig. 5. Average waiting time for junction 5.


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as vehicle type, license ID, it will become an electronic tag, which can be used in multiple

applications in transportation system, such as ETC (electronic Toll Collection), Parking

Management and so on.

3) After vehicle unit being installed on most vehicles, the traffic information can exchange

among vehicles, that is, the roadside unit is not necessary. Wireless sensor networks offer a


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promising platform for traffic monitoring that can compete with current technology in

accuracy and lifetime. We have built a prototype of the sensor node for traffic surveillance.

More intersection flow policy need to be investigated for the intersection agent to be able

to decide the best flow policy depending on information received from the sensor network.

6- How does a traffic light detect that a car has pulled up and is waiting for

the light to change?

There is something exotic about the traffic lights that "know" you are there -- the instant

you pull up, they change! How do they detect your presence?

Some lights don't have any sort of detectors. For example, in a large city, the traffic lights

may simply operate on timers -- no matter what time of day it is, there is going to be a lot of

traffic. In the suburbs and on country roads, however, detectors are common. They may

detect when a car arrives at an intersection, when too many cars are stacked up at anintersection (to control the length of the light), or when cars have entered a turn lane (in

order to activate the arrow light).

There are all sorts of technologies for detecting cars -- everything from lasers to rubber

hoses filled with air! By far the most common technique is the inductive loop. An inductive

loop is simply a coil of wire embedded in the road's surface. To install the loop, they lay the

asphalt and then come back and cut a groove in the asphalt with a saw. The wire is placed in

the groove and sealed with a rubbery compound. You can often see these big rectangular

loops cut in the pavement because the compound is obvious.Inductive loops work by

detecting a change of inductance. To understand the process, let's first look at whatinductance is. The illustration on this page is helpful.

What you see here is a battery, a light bulb, a coil of wire around a piece of iron (yellow),

and a switch. The coil of wire is an inductor. If you have read How Electromagnets Work,

you will also recognize that the inductor is an electromagnet. Ads by Google

If you were to take the inductor out of this circuit, then what you have is a normal flashlight.

You close the switch and the bulb lights up. With the inductor in the circuit as shown, the

behavior is completely different. The light bulb is a resistor (the resistance creates heat to

make the filament in the bulb glow). The wire in the coil has much lower resistance (it's just

wire), so what you would expect when you turn on the switch is for the bulb to glow very

dimly. Most of the current should follow the low-resistance path through the loop. What

happens instead is that when you close the switch, the bulb burns brightly and then gets

dimmer. When you open the switch, the bulb burns very brightly and then quickly goes out.


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The reason for this strange behavior is the inductor. When current first starts flowing in the

coil, the coil wants to build up a magnetic field. While the field is building, the coil inhibits

the flow of current. Once the field is built, then current can flow normally through the wire.

When the switch gets opened, the magnetic field around the coil keeps current flowing in

the coil until the field collapses. This current keeps the bulb lit for a period of time even

though the switch is open.

The capacity of an inductor is controlled by two factors:

* The number of coils

* The material that the coils are wrapped around (the core)

Putting iron in the core of an inductor gives it much more inductance than air or any other

non-magnetic core would. There are devices that can measure the inductance of a coil, and

the standard unit of measure is the henry.

So... Let's say you take a coil of wire perhaps 5 feet in diameter, containing five or six loops

of wire. You cut some grooves in a road and place the coil in the grooves. You attach an

inductance meter to the coil and see what the inductance of the coil is. Now you park a car

over the coil and check the inductance again. The inductance will be much larger because of

the large steel object positioned in the loop's magnetic field. The car parked over the coil is

acting like the core of the inductor, and its presence changes the inductance of the coil.

A traffic light sensor uses the loop in that same way. It constantly tests the inductance of the

loop in the road, and when the inductance rises, it knows there is a car waiting

7-Deployed Airbag

For years, the trusty seat belt provided the sole form of passive restraint in our cars. There

were debates about their safety, especially relating to children, but over time, much of the

country adopted mandatory seat-belt laws. Statistics have shown that the use of seat belts

has saved thousands of lives that might have been lost in collisions.

Like seat belts, the concept of the airbag -- a soft pillow to land against in a crash -- has been

around for many years. The first patent on an inflatable crash-landing device for airplanes

was filed during World War II. In the 1980s, the first commercial airbags appeared in auto

Since model year 1998, all new cars sold in the United States have been required to have

airbags on both driver and passenger sides. (Light trucks came under the rule in 1999.) To

date, statistics show that airbags reduce the risk of dying in a direct frontal crash by about

30 percent. Then came seat-mounted and door-mounted side airbags. Today, some cars go

far beyond having dual airbags to having six or even eight airbags. Having evoked some of

the same controversy that surrounded seat-belt use in its early years, airbags are the

subject of serious government and industry research and tests.


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In this article, you'll learn about the science behind the airbag, how the device works, what

its problems are and where the technology goes from here.

Laws of Motion

Before looking at specifics, let's review our knowledge of the laws of motion. First, we know

that moving objects have momentum (the product of the mass and the velocity of an

object). Unless an outside force acts on an object, the object will continue to move at its

present speed and direction. Cars consist of several objects, including the vehicle itself,

loose objects in the car and, of course, passengers. If these objects are not restrained, they

will continue moving at whatever speed the car is traveling at, even if the car is stopped by a

collision.

Stopping an object's momentum requires force acting over a period of time. When a car

crashes, the force required to stop it

What an airbag wants to do is to slow the passenger's speed to zero with little or nodamage. The constraints that it has to work within are huge. The airbag has the space

between the passenger and the steering wheel or dashboard and a fraction of a second to

work with. Even that tiny amount of space and time is valuable, however, if the system can

slow the passenger evenly rather than forcing an abrupt halt to his or her motion.

8-Airbag Inflation

The goal of an airbag is to slow the passenger's forward motion as evenly as possible in a

fraction of a second. There are three parts to an airbag that help to accomplish this feat:The

airbag and inflation system stored in the steering wheel.

* The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or

dashboard or, more recently, the seat or door.

* The sensor is the device that tells the bag to inflate. Inflation happens when there is a

collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per

hour). A mechanical switch is flipped when there is a mass shift that closes an electrical

contact, telling the sensors that a crash has occurred. The sensors receive information from

an accelerometer built into a microchip.

* The airbag's inflation system reacts sodium azide (NaN3) with potassium nitrate (KNO3)to produce nitrogen gas.

The airbag and inflation system stored in the steering wheel. See more car safety images.

Early efforts to adapt the airbag for use in cars bumped up against prohibitive prices and

technical hurdles involving the storage and release of compressed gas. Researchers

wondered:


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* If there was enough room in a car for a gas canister

* Whether the gas would remain contained at high pressure for the life of the car

* How the bag could be made to expand quickly and reliably at a variety of operating

temperatures and without emitting an ear-splitting bang

The inflation system uses a solid propellant and an igniter. They needed a way to set off a

chemical reaction that would produce the nitrogen that would inflate the bag. Small solid-

propellant inflators came to the rescue in the 1970s.

The inflation system is not unlike a solid rocket booster (see How Rocket Engines Work for

details). The airbag system ignites a solid propellant, which burns extremely rapidly to

create a large volume of gas to inflate the bag. The bag then literally bursts from its storage

site at up to 200 mph (322 kph) -- faster than the blink of an eye! A second later, the gas

quickly dissipates through tiny holes in the bag, thus deflating the bag so you can move.

Even though the whole process happens in only one-twenty-fifth of a second, the additional

time is enough to help prevent serious injury. The powdery substance released from the

airbag, by the way, is regular cornstarch or talcum powder, which is used by the airbag

manufacturers to keep the bags pliable and lubricated while they're in storage.

9-Airbag Safety Concerns

Since the early days of auto airbags, experts have cautioned that airbags are to be used in

tandem with seat belts. Seat belts were still completely necessary because airbags workedonly in front-end collisions occurring at more than 10 mph (6 kph). Only seat belts could

help in side swipes and crashes (although side-mounted airbags are becoming more

common now), rear-end collisions and secondary impacts. Even as the technology advances,

airbags still are only effective when used with a lap/shoulder seat belt.

It didn't take long to learn that the force of an airbag can hurt those who are too close to it.

Researchers have determined that the risk zone for driver airbags is the first 2 to 3 inches (5

to 8 cm) of inflation. So, placing yourself 10 inches (25 cm) from your driver airbag gives you

a clear margin of safety. Measure this distance from the center of the steering wheel to your

breastbone. If you currently sit less than 10 inches away, you can adjust your drivingposition in the following ways:

* Move your seat to the rear as far as possible while still reaching the pedals comfortably.

* Slightly recline the back of your seat. Although car designs vary, most drivers can

achieve the 10-inch distance even with the driver seat all the way forward by slightly

reclining the back of the seat. If reclining the seat makes it hard to see the road, you can


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raise yourself up by using your car's seat-raising system (not all cars have this!) or a firm,

non-slippery cushion to achieve the same effect.

* Point the airbag toward your chest, instead of your head and neck, by tilting your

steering wheel downward (this only works if your steering wheel is adjustable).

The rules are different for children. An airbag can seriously injure or even kill an unbuckled

child who is sitting too close to it or is thrown toward the dash during emergency braking.

Experts agree that the following safety points are important:

* Children 12 and under should ride buckled up in a properly installed, age-appropriate

car seat in the rear seat.

* Infants in rear-facing child seats (under one year old and weighing less than 20 pounds /

10 kg) should never ride in car

If a child over one year old must ride in the front seat with a passenger-side airbag, he or

she should be in a front-facing child safety seat, a booster seat or a properly fitting

lap/shoulder belt, and the seat should be moved as far back as possible. For more

information about child car seats, read Car Seats: Fast Facts.

In certain special cases, car owners can request the ability to deactivate their airbags. In the

next section, we'll discuss steps to take if you want to have your airbag deactivated.

10-Airbag Deactivation

In response to concerns about children -- and others, especially smaller people -- being

killed or seriously injured by malfunctioning or overly powerful airbags, the NationalHighway Traffic Safety Administration (NHTSA) in 1997 issued a final rule to allow auto

manufacturers to use lower-powered airbags. This rule permits airbags to be depowered by

20 to 35 percent. In addition, starting in 1998, repair shops and dealers were allowed to

install on/off switches that allow airbags to be deactivated. Vehicle owners could now be

authorized (by the NHTSA) to get on/off switches installed for one or both airbags in their

car if they (or other users of their car) fell into one or more of these specific risk groups:

* For both driver and passenger sides - Individuals with medical conditions in which the

risks of deploying the airbag exceed the risk of impact in the absence of an airbag

* For the driver side (in addition to medical conditions) - Those who cannot position

themselves to properly operate their cars at least 10 inches (25.4 cm) back from the center

of the driver airbag cover

* For the passenger side (in addition to medical conditions) - Individuals who need to

transport a baby in a rear-facing child restraint in the front seat because the car has no rear


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seat, the rear seat is too small to accommodate a rear-facing child seat or because it's

necessary to constantly monitor a child's medical condition

* For the passenger side (in addition to medical conditions) - Individuals who need to

carry children between one and 12 years old in the front seat because (a) the car has no rear

seat, (b) the vehicle owner must carry more children than can fit into the back seat or (c)because it's necessary to constantly monitor a child's health

If you would like to get an on-off switch installed in your car, you need a copy of NHTSA's

brochure, "airbags and On-Off Switches: Information for an Informed Decision," and the

accompanying form, Request for airbag On-Off Switch. You can find these on the NHTSA

Web site, as well as at AAA clubs, new-car dealers and state motor vehicle departments. The

NHTSA will send you a letter of authorization that you can take to a repair shop. (Before you

bother with all this, you should check with your auto dealer or repair shop to see if an on-off

switch is available for your car.) Some retrofit on-off switches can be found and used if

federal requirements are met -- switches must be operated by a key and equipped withwarning lights to indicate whether the bags are turned off or on.

Obviously, even you have the option of turning it off, the airbag should be left on for drivers

who can sit at least 10 inches back. For those who can't (even with the suggestions listed

above), the bag can be turned off. A group of doctors at the National Conference on Medical

Indications for airbag Deactivation considered the medical conditions commonly reported in

letters to the NHTSA

possible justification for turning off airbags. They did not, however, recommend turning off

airbags for relatively common conditions, such as:

* pacemakers

* eyeglasses

* angina

* emphysema

* asthma

* mastectomy

* previous back or neck surgery

* advanced age

* osteoporosis

* arthritis


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* pregnancy

Generally speaking, you can't deactivate your airbag without installing a retrofit on-off

switch. However, if a retrofit on-off switch is not yet available (from the vehicle

manufacturer) for your car, the NHTSA will authorize airbag deactivation on a case-by-case

basis under appropriate conditions. Never try to disable the bag yourself -- remember, thisis no soft cushion! It packs a wallop and can hurt you when you don't know what you're

doing.

As for factory-installed on-off switches, the NHTSA allows car manufacturers to install

passenger airbag on-off switches in new vehicles under limited circumstances -- only if the

vehicle has no rear seat or if the rear seat is too small to accommodate a rear-facing child

safety seat. And manufacturers are not currently allowed to install on-off switches for the

driver airbag in any new vehicle. Why these rules? The NHTSA decided against widespread

factory-installed on-off switches for fear that they would become standard equipment in all

new vehicles -- even those purchased by people not in at-risk groups. They also saw theintegration of on-off switches into new cars (and the subsequent redesign of instrument

panels) as something that would divert resources from the development of safer, more

advanced airbag systems.

Next, we'll look at some of the safety cautions associated with airbags, especially where

children are concerned

11-REFERENCES

[1] Sing Yiu Cheung, Sinem Coleri, Baris Dundar, Sumitra Ganesh, Chin-Woo Tan, and Pravin

Varaiya. Traffic measurement and vehicle classification with a single magnetic sensor.

Journal of the Transportation Research Board, February 2006.

[2] Ana L. C. Bazzan. A distributed approach for coordination of traffic signal agents.

AutonomousAgentsand Multi-Agent Systems, 10(2):131 164, 2005.

[3] Kurt M. Dresner and Peter Stone. Multiagent traffic management: an improved

intersection control mechanism. In 4rd International Joint Conference on Autonomous

Agentsand Multiagent Systems (AAMAS2005), July 25-29, 2005, Utrecht,The Netherlands,

pages 471477. ACM, 2005.


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[4] Marco Wiering, Jilles Vreeken, Jelle van Veenen, and Arne Koopman. Simulation and

optimization of traffic in a city. In IEEEIntelligentVehiclessymposium (IV04), June 2004.

[5] Wenjie Chen, Lifeng Chen, Zhang long Chen, and Shi liang Tu. Wits: A wireless sensor

network for intelligent transportation system. In Interdisciplinary and Multidisciplinary

Research in Computer Science, I

EEE CS Proceeding of the First International Multi-

Symposium of Computer and Computational Sciences (IMSCCS06), June 20-24, 2006,

Zhejiang University, Hangzhou,China, Vol. 2, pages 635641. IEEE Computer Society, 2006.

[6] Bret Hull, Vladimir Bychkovsky, Yang Zhang, Kevin Chen, Michel Goraczko, Allen K. Miu,

Eugene Shih, Hari Balakrishnan, and Samuel Madden. Cartel: A distributed mobile sensor

computing system. In 4th

ACM SenSys, Boulder, CO, November 2006.

[7] Denise de Oliveira, Ana L. C. Bazzan, and Victor R. Lesser. Using cooperative mediation to

coordinate traffic lights: a case study. In 4rdInternationalJointConference on Autonomous

Agentsand MultiagentSystems (AAMAS 2005), July 25-29, 2005, Utrecht,The Netherlands,

pages 463470. ACM, 2005.

[8] Lifeng Chen, Zhanglong Chen, and Shiliang Tu. A realtime dynamic traffic control system

based on wireless sensor network. In ICPPW 05: Proceedings of the 2005 International

Conference on ParallelProcessingWorkshops (ICPPW05), pages 258264, Washington, DC,

USA, 2005. IEEE Computer Society 1-4244-0667-6/07/$25.00 2007 IEEE 191 Authorized

licensed use limited to: INDIAN INSTITUTE OF SCIENCE. Downloaded on June 22, 2009 at

09:33 from IEEE Xplore. Restrictions apply.

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