1.1 first signal lighting could be attributed to



1.1       Introduction

Traffic lights, or traffic signals, are located on most
major corners in cities and towns around the world. The red, yellow and green
lights let us know when it is safe to drive through the intersection and when
to walk across the street as well as when to stop and let other drivers,
bikers, and pedestrians take their turns to continue their way.

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1.2       History of Traffic Signals

However, only one month later, a police officer controlling
the signal was badly injured when a leak in a gas main caused one of the lights
to explode in his face. The project was declared a public health hazard and
immediately dropped.

The first signal lighting could be attributed to the use of
campfires and flaming markings by prehistoric man to guide fishermen back to
their tribes. There are historical references to regularly maintained traffic
lights on towers dating back to 2600 years ago. The most famous of these early
structures, and probably the tallest tower ever housing a traffic light, was
the Pharos of Alexandria, Egypt. Built around 230 B.C., this structure has
dominated some 400 feet in the air. He survived two civilizations and survived
the Roman Empire by nine centuries. This marine lighthouse was truly a wonder
of the world in its time. With respect to land transport, you have to look at
the railways, where the signaling lights have been well established. As early
as 1857, lanterns suspended from a crossbar gave the railwaymen a signal of
blockage visible both at night and during the day. In 1905, block signals were
mostly semaphores with colored disks transmitting light from oil lamps at
night. Regarding the control or direction of road traffic by colored fires,
Britain probably saw for the first time what we now consider to be traffic
lights. A native of Bradford, England, who was a mill worker much more than a
hundred years ago, seems to have had the idea of controlling traffic by means
of colored lights. He built a control device using oil lamps that were
alternately revealed and concealed by means of a shutter. Like many other
serious inventors, before and after his time, he sought to inform the
government of the administration of his ingenious device and what he would do.
Officials remained convinced, however, that the police should control traffic,
and the disappointed inventor walked back and forth to his Bradford factory to
stay in the dark. It was up to a railway signal manufacturer company to
successfully build the world’s first traffic light using colored lights, in
response to a suggestion made in 1866 by a select committee in London
recommending the adoption of railway equipment. In mid-December 1868, a
“beautiful” semaphore was installed at the intersection of George and
Bridge Streets, near the Houses of Parliament, to protect members of the
parliament who had to negotiate traffic flows. This semaphore was 22 feet tall
and had the appearance of a hydra. Crowned with a gas light for visibility, the
semaphore arms when extended in a horizontal position meant
“stopping”. Then lowered to a “falling” angle of 45 ‘the
message “attention”. At night, a green light was used with the
“attention” position and a red light with the “stop”
position. Richard Alayne, the police commissioner of London, explained the
semaphore’s meaning by a proclamation.

Charles J. Reading, a municipal electrician in Salt Lake
City, Utah, in 1916 or 1917, installed a signal of his own design (built by Mr.
Carter, a local tinsmith) that featured red and green lenses in four
directions. It consisted of a sheet metal construction, it was circular in
shape and about 20 inches in diameter, and it had eight standard railway
signaling lenses, about 8 inches in diameter. It was installed in the middle of
the intersection and was controlled by a policeman in a corner.

In December 1920, the use of all three traffic signals
(green, yellow and red) were used for the first time following an installation
in Michigan and Woodward avenues in Detroit. The signals interpreted “go, clear
the intersection and stop” for the green, yellow and red signals respectively.

The first interconnected traffic light system was installed
in Salt Lake City in 1917, with six connected intersections controlled
simultaneously from a manual switch. Automatic Control of Interconnected
Traffic Lights was introduced in March 1922 in Houston, Texas 1

1.3       Competing Patents

Following the accident, about four decades passed before
traffic signals began to grow in popularity again, mainly in the United States
as more automobiles hit the road. The early 1900s saw several patents being
filed, each with a different innovation to the basic idea.

In 1910, Ernest Sirrine, an American inventor, introduced an
automatically controlled traffic signal in Chicago. His traffic signal used two
non-illuminated display arms arranged as a cross that rotated on an axis,
according to Inventor Spot. The signs said “stop” and

The first electric traffic light using red and green lights
was invented in 1912 by Lester Farnsworth Wire, a police officer in Salt Lake
City, Utah, according to Family Search. Wire’s traffic signal resembled a
four-sided bird-house mounted on a tall pole. It was placed in the middle of an
intersection and was powered by overhead trolley wires. A police officer had to
manually switch the direction of the lights.

However, the credit for the “first electric traffic
signal” usually goes to James Hoge. A system based on his design was
installed on Aug. 5, 1914, in Cleveland. Hoge received a patent for the system
in 1918. (He had filed his application in 1913.) Hoge’s traffic signal used the
alternating illuminated words “stop” and “move” installed
on a single post on each of the four corners of an intersection. The system was
wired such that police and fire departments could adjust the rhythm of the lights
in case of an emergency.

William Ghiglieri of San Francisco patented the first
automatic traffic signal that used red and green lights in 1917. Ghiglieri’s
design had the option of being either automatic or manual.

Then in 1920, William Potts, a Detroit police officer, developed
several automatic traffic light systems, including the first three-color
signal, which added a yellow “caution” light.

In 1923, Garrett Morgan patented an electric automatic
traffic signal. Morgan was the first African-American to own a car in Cleveland.
He also invented the gas mask. Morgan’s design used a T-shaped pole unit with
three positions. Besides “Stop” and “Go,” the system also
first stopped traffic in all directions to give drivers time to stop or get
through the intersection. Another benefit of Morgan’s design was that it could
be produced inexpensively, thus increasing the number of signals that could be
installed. Morgan sold the rights to his traffic signal to General Electric for

The first electric traffic light in Europe was installed in
1924 at Potsdamer Platz in Berlin, according to Marcus Welz, CEO of Siemens ITS
(Intelligent Traffic Systems) US. The five-sided traffic light was mounted on a
tower and was primarily manual with some automation, which only required a
single police officer to manage. A replica now stands nearby and is a popular
tourist attraction.

Pedestrian signals began to be included in traffic signals
in the 1930s, according to the U.S. Department of Transportation. A
“Walk/Don’t Walk” signal was first tested in New York in 1934. It
even used an upright palm to indicate “Stop.”

John S. Allen, an American inventor, filed one of the
earliest patents in 1947 for a dedicated pedestrian traffic signal. Allen’s
design had the pedestrian signal mounted at curb level. Allen also proposed
that the signals could contain advertisements. In his application, he explained
that the words “Stop” and “Go” could be followed by the
word “for,” which in turn would be followed by a brand name. 1


1.4       Effects of Traffic Congestion

Congestion is a situation in which demand for road space
exceeds supply. Congestion is the impedance vehicles impose on each other, due
to the speed-flow relationship, in conditions where the use of a transport
system approaches capacity. 5


1.5       Causes of Traffic Congestion

Poor road traffic management is the primary reason for
extended periods of traffic congestion throughout the world. The worst traffic
in the world occurs in Brazil, where people are stuck in traffic for up to
about 3 three hours per day. The issue of road congestion has affected both
developing economies developed to varying degrees’ measures taken to contain
the problem. Most urban areas have a critical congestion area where a large
network of roads converge and large traffic needs to traverse, for example, the
toll gate that connects Ozumba Mbadiwe and Lekki Epe expressway. Also, rapid
burst in traffic over short periods of time can cause a catastrophic spiraling
effect which will lead to a congestion collapse. In developing countries such
as Nigeria, the issue of massive traffic explosion has worsened due to the
following reasons:

Unplanned cities: cities and urban areas grow in
an ad-hoc manner. With the growth, adequate provision towards scaling the
capacity in which roads can take is just not made. The lack of provision with
respect to the growth leads to bottleneck roads.

Poor discipline: often we see drivers jump red
lights, have poor lane discipline or even aren’t fully educated about traffic
rules and regulations and block the intersection. This leads to traffic
congestion. Furthermore, poor traffic law enforcement sometimes gives no
incentive for drivers to obey the traffic rules.

Out-of-date management: traffic centers are
often uninhabited, allowing drivers to drive in a chaotic manner. Even if a
union is controlled by a policeman or a traffic light, the traffic junctions
are largely independent of any traffic management strategy, optimizing only the
respective trunk traffic flow, in the sense of maximum traffic accumulation. In
addition, these approaches reinforce mismanagement of traffic on already
congested roads, accelerating the congestion collapse

Tighter budgets: A significant amount of
investment is required to set up a traffic management infrastructure which can
scale with the increasing traffic. Such an infrastructure not only involves
measuring and analyzing real-time traffic data but also focuses towards
enhancing congestion detection, solving real-time congestion and forecasting
congestion scenarios. In developing countries, ravaged by corruption and
bureaucracy, there are multiple hurdles before the money actually progresses
towards such large initiatives.  2

Also, the causes of traffic congestion can be subdivided
into 2 categories, which are the recurrent and non-recurrent categories. The
recurrent congestion category covers congestion that occurs due to events that
happen on a regular. They include physical capacity limitation, poor road
network etc. while the nonrecurring congestion refers to congestion caused by events
which occur in a manner that isn’t regular. They include accidents, police
checks, road closures due to construction and some others. 4

Causes of congestion in Nigeria

Bashiru and Waziri (2008) highlighted the main causes of
traffic congestion in Lagos to be attributed to the following: illicit parking
on the street, high volume of vehicles on the road, narrow road, inadequate
traffic light at certain intersections, flooding and poor drainage, loading and
discharging of passengers. Even though the items listed above are not
exhaustive of the causes of traffic congestion, Aworemi et al (2009) also
agreed to the findings of Bashiru and Waziri after conducting a study with a
case study on Lagos. To buttress the findings a survey was conducted at the Annual
General Meeting (AGM) of the Nigerian Society of Engineers (NSE) where
questionnaires were distributed among participants. The results from the
respondents are shown in table 1. 5


Table 1 Causes of Traffic Congestion
in Nigeria


Causes of congestion




Poor driving habits




Poor parking habits




Poor road network




Inadequate road capacity




Lack of parking facilities




Poor traffic control management




Poor drainage




Presence of heavy vehicles




Poorly designed junction/roundabout




Lack of efficient mass transit




Lack of pedestrian facility




Malfunctioning vehicles




Poor road pavement




Presence of construction activities




Lack of road furniture




Too many taxis




Excessive speeding




Frequent use of sirens




Poor weather







Causes of traffic congestion gotten from the International
Journal of Engineering and Technology Volume 2 No. 8, August 2012


1.6       Advantages

The most obvious reason for the use of intelligent traffic
control system (ITCS) which is also known as adaptive traffic control system is
due to the increase in traffic congestion and the daily and weekly fluctuations
in traffic flow. For instance, using Lagos as case study, there is usually
heavy traffic congestion around the hours of 6-8am during working days, that
is, Monday to Friday. Also there are uncertainties (non-recurring events) such
as accidents, road construction or even any construction activity by the road,
flooding etc. that may rapidly increase traffic congestion in areas. All these
factors put into consideration is what gave rise to intelligent traffic control
systems. Some of the benefits of intelligent/adaptive traffic control systems
are listed below:

Responds well to emergency vehicle preemption
and traffic congestion resulting from crashes, clears back-ups quickly.

Response to day-to-day and TOD fluctuations in

If traffic demand is light the cycle was lower
and more accommodating.

It does well when traffic flow is incremental,
not when there are turbulent fluctuations in volume and demand.

Coordination between signals, handling special
events, changes in traffic volumes and patterns, and tourist area traffic.

Ability to quickly respond to traffic

Covers special sequence operations.

Responds well to large volumes of traffic
exiting on side streets that do not happen according to a regular schedule
(e.g., a themed water park emptying as the result of a thunderstorm).

Provides detailed information of traffic signal
from central office.

Maximizes throughput.

Network control is delivered effortlessly. 12

1.7       Use
of Sensors and Technology in Traffic Management

according to the Advanced English dictionary, a sensor is
defined as any device that receives a signal or stimulus (as heat or pressure
or light or motion etc.) and responds to it in a distinctive manner. With the
ever-growing rise and rapid increase in population which in turns gives rise to
an increase in the number of commuters and vehicles on road networks, it is no
news that urban areas need to adopt an intelligent traffic system (ITS) to
tackle this challenge. The use of sensors and technology has not only aided
this development, but it has also helped in forecasting through studying the
patterns and behaviors during hours of days in certain road networks. 3

Some of the technology used in traffic detection and
management are:

Inductive loop detectors: of all the sensors and
technology used, this is the most common. The loops vary in size and are
powered using sinusoidal ac voltage. It generates a magnetic field around the
loop which are usually installed below the surface of the road, therefore when
a vehicle (a metal object) such a bus or car passes over the inductive loop,
there are changes in the inductances of the loop. 6 These loops are also
connected to a computer where the data gotten from the changes in the
inductance of the loops serve as counters for the number of vehicles traveling
a particular lane. The initial drawback to this method was that, it was not
able to accurately detect vehicles in the cases of chaotic traffic congestion,
that is, non-lane based traffic congestion. The introduction of multiple loop
detectors placed side by side have been able to efficiently detect this type of
traffic. 7

1 example of an inductive loop

Figure 2 Changes in inductance when a
vehicle passes over an inductive loop. Reproduced from IEEE Transactions on
Instrumentation and Measurement, Vol. 61, No. 5, May 2012


Acoustic sensors: Vehicles always produce
various sounds, and depending on its speed, mechanical conditions and load.
These vehicles produced noises can be categorized under the following:

Engine noise: An internal combustion engine’s
noise consists of a deterministic harmonic train and a stochastic noise
component due to the air intake. Engine noise vary due to the acceleration and
speed of the vehicle. For instance, in the case of high traffic congestion, an
engine-idling noise is produced as long as the ignition is on.

Tire noise: this noise is produced as a result
of the interaction between the surface of the road and the tire itself. It
consists of 2 main components which are the air noise and the vibrational
noise. The air noise is produced as a result of the air being sucked and the
vibrational noise is produced as a result of the contact between the road
surface and the tire. The noise produced by the tire in a vehicle moving at
above 50km/h is the main source of the total noise produced by that vehicle,
therefore its acoustic signals around that speeds could provide vital
information in the determination of traffic congestion.

Air Turbulence noise: As a vehicle moves at
medium to high speeds, it induces air turbulence. This noise is due to the air
flow generated by the boundary layer of the vehicle and is most prominent
immediately after a vehicle has driven past the microphone as a distinctive
drive-by-noise or whoosh sound.

Exhaust noise: this noise is produced by the
exhaust system that connects the engine compartment to the rear end of the
vehicle through the exhaust tubes.  An
increase in the load of the vehicle will cause an increase in the exhaust

Honks: presence of loud and frequent honk noise
is accustomed to presence of traffic congestion.

Therefore, in relation to the signals and
the behavior that generates these signals, it is possible to detect, analyze
and also manage traffic congestion. It is also efficient in cases of chaotic
traffic congestion. 8

Infrared sensors: The use of infrared sensors
can be applied in traffic monitoring in the cases of active and passive
infrared sensors.  Active infrared
sensors provide data on vehicle presence at traffic signals, volume, speed,
length, and queue measurement. Passive IR sensors can measure vehicle counting,
volume, lane occupancy detection, and queue detection. 10

Image sensors: Some studies (Palubinskas et al.,
2008 Long Chen et al., 2008) using images such as video surveillance, deployed
on the edge of the road and measure the level of congestion by image processing
techniques. The slower the image changes over time the higher the level of
congestion. 9

Probe vehicle based sensors: Probe vehicles are
vehicles that are part of traffic and equipped with various sensors like GPS
receiver, accelerometer, Distance Measuring instruments (DMI), etc. to measure
various parameters such as speed with which traffic is moving, road surface
condition etc. 9

All these technologies and techniques that aid in traffic
detection, monitoring and management have limitations and drawbacks, some of
which are highlighted below:

Technique Drawbacks

Loop detectors: high cost, under-the-road
installation and also high cost of maintenance.

Video and images:  not proven solutions for chaotic traffic thus
far, potentially high computation and/or communication overhead for chaotic

IR (Infrared) sensors: the presence of
pedestrians, road surface irregularities and non-lane based vehicular movement
cause spurious beam cuts therefore making the data inaccurate.

Acoustic sensors: high training overhead, slow

Probe sensors: useful for complementary applications,
but too sparse and noisy to allow micro management of road network. 11




1 Edward A. Mueller. Aspects of the
History of Traffic Signals. IEEE
Transactions Of Vehicular Technology, Vol. Vt-19, No. 1

2 Jain, V., Sharma, A., & Subramanian, L. (2012, March).
Road traffic congestion in the developing world. In Proceedings of the
2nd ACM Symposium on Computing for Development (p. 11). ACM

3 Chong, C. Y., & Kumar, S. P. (2003). Sensor networks:
evolution, opportunities, and challenges. Proceedings of the IEEE, 91(8),

4 Chow, A. H., Santacreu, A., Tsapakis, I., Tanasaranond, G.,
& Cheng, T. (2014). Empirical assessment of urban traffic congestion. Journal
of advanced transportation, 48(8), 1000-1016.

5 Ukpata, J. O., & Etika, A. A. (2012). Traffic congestion
in major cities of Nigeria. International Journal of Engineering and
Technology, 2(8), 1433-1438.

6 Gajda, J., Piwowar, P., Sroka, R., Stencel, M., & Zeglen,
T. (2012). Application of inductive loops as wheel detectors. Transportation
Research Part C: Emerging Technologies, 21(1), 57-66.

7 Ali, S. S. M., George, B., Vanajakshi, L.,
& Venkatraman, J. (2012). A multiple inductive loop vehicle detection
system for heterogeneous and lane-less traffic. IEEE Transactions on
Instrumentation and Measurement, 61(5), 1353-1360.

8 Tyagi,
V., Kalyanaraman, S., & Krishnapuram, R. (2012). Vehicular traffic density
state estimation based on cumulative road acoustics. IEEE Transactions
on Intelligent Transportation Systems, 13(3), 1156-1166.

9 Rao,
A. M., & Rao, K. R. (2012). Measuring Urban Traffic Congestion-A Review. International
Journal for Traffic & Transport Engineering, 2(4).

Tewolde, G. S. (2012, May). Sensor and network technology for intelligent transportation
systems. In Electro/Information Technology (EIT), 2012 IEEE
International Conference on (pp. 1-7). IEEE.

Sen, R., Maurya, A., Raman, B., Mehta, R., Kalyanaraman, R., Vankadhara, N.,
… & Sharma, P. (2012, November). Kyun queue: a sensor network system to
monitor road traffic queues. In Proceedings of the 10th ACM Conference
on Embedded Network Sensor Systems (pp. 127-140). ACM.

12 “Studies
about Safety Benefits of Adaptive Traffic Control Systems” (2013, November 6)
Retrieved from https://cdn2.hubspot.net/hub/65632/file-368346571-pdf/docs/studies_about_safety_benefits_of_adaptive_traffic_control_systems.pdf