Chapter-1ppt.pptx

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Traffic Safety and Environmental Impacts: - CENG 6306-
Lectured By:- Solomon N (PhD)

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Outlines
 Fundamentals of Traffic Engineering
 Basic Characteristics of Motor-Vehicle Traffic,
 Highway Capacity,
 Applications of Traffic Control Devices,
 Traffic Design of Parking Facilities,
 Traffic Engineering Studies;
 Statistical Methods in Traffic Safety Analysis
 Regression Methods,
 Poisson distribution,
 Chi- Squared Distribution,
 Statistical Comparison

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Fundamentals of Traffic Engineering
 The Road Traffic and Safety Engineering Unit is
responsible for traffic engineering activities within the
road traffic environment, ensuring efficient and effective
coordination among the three spheres of government in
order to reduce fragmentation on the roads.
Management traffic includes three categories:
management, monitoring, and data backups and
restores.
 Traffic engineers work to ensure that our roads are
safe for everyone. They are constantly monitoring
traffic conditions and looking for ways to improve
safety. Some of the ways they promote safer traffic
conditions include adding traffic signals, changing the
timing of existing signals, and adding turning lanes.

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 Traffic management (also known as road traffic control)
refers to the act of directing vehicles and pedestrians
around some form of disruption.
 Traffic management is the application of specific traffic
control practices, within a defined policy framework,
over a length of road or an area, to achieve specified
objectives which may be set by national, state or local
governments.
 Proper traffic management can ensure that: traffic
flows smoothly and efficiently. There is fair access for
different transport modes, and the more sustainable
modes are encouraged. Roads and streets are safe for
all users, including pedestrians and cyclists.

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 Traffic management involves supporting workers on
the road by providing safety equipment such as cones
and barrier fences, as well as putting up traffic lights
and diverting traffic through a series of road closures
and diversions.
 Implement traffic management techniques: Congestion
pricing, roundabouts, and traffic signals are some
examples of traffic management techniques that can
help manage traffic flow and ease congestion.
 There are four basic elements in a computerized traffic
control system: computer(s), communications devices,
traffic signals and associated equipment, and detectors
for sensing vehicles.

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 Road Traffic Control Systems collect and analyze
driving information of vehicles in the area, perform the
optimal traffic signal control in accordance with the
constantly changing road traffic situation, and provide
useful traffic information to drivers based on the data
collected.
 Traffic is often classified by type: heavy motor vehicle
(e.g., car, truck), other vehicle (e.g., moped, bicycle),
and pedestrian.

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The key functions of RT & SE
The key functions of the unit are as follows:
 To identify and implement traffic and road safety
engineering technological interventions.
 To address the problem areas within road safety with
regard to freight transport, viz. overloading and
abnormal loads.
 Eliminate high risk roads and hazardous locations.
 Improve the standards of road design to ensure that
all road users are given adequate protection and
information with special focus on Vulnerable Road
Users (VRUs), especially pedestrians.
 Ensure that road design is forgiving, thus allowing
motorists to recover from error, or to incur least harm
when a crash is inevitable.

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 Ensure the inherent safety (safety by design) in the
provision of new and upgraded road infrastructure.
 Develop road safety auditor, road safety assessment
and road safety engineering capacity.
 Develop a culture of road safety among those
responsible for the delivery and maintenance of road
infrastructure.
 To intensify efforts to deal with inattentive, distracted
driving and fatigue as a factor for consideration in
road infrastructure design.

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 To intensify efforts to deal with speeding and
determine appropriate speed limits.
 Utilize technology to improve incident detection
response and coordination.
 To assess the distribution of emergency response for
road infrastructure to be geospatially adapted where
possible to ensure optimal access and response to
incidents.

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The following factors affect traffic characteristics as
follows:
 vision.
 hearing.
 strength.
 reaction time.
 judgment power.
 fatigue.
 anger.
 climatic conditions.
Traffic Characteristics

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Basic Traffic Characteristics in transport engineering are
an important aspect that covers two major
characteristics in the study of transportation engineering.
 Traffic characteristics are necessary for road design.
 Traffic characteristics also help in the design of
vehicles.
 In road design, traffic characteristics help in deciding
speed limit, stopping sight distance, overtaking sight
distance, design of traffic islands, speed of the
vehicle, design of parking, right of way, etc.
 The weight of vehicles, the height of vehicles, and
other aspects of vehicle design too require an
understanding of traffic characteristics.

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 Placing signs and symbols on the road also needs
knowledge of road user characteristics. The color of
these signs, symbols, and other elements of the
road are decided after considering traffic
characteristics.
 Traffic characteristics also play an important role in
tunnel design

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Types of Traffic Characteristics
Types of Traffic Characteristics in Transport Engineering
There are two main types of basic traffic characteristics
as follows:
 Road user characteristics: are the characteristics
related to the road users, i.e., the public making use of
the road. We all use roads whether to drive our
vehicles or by walking on foot. Thus, traffic
characteristics are essentially human characteristics
that can affect road design.
 Vehicular (Motor-vehicles) characteristics:-

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Types of Road User Characteristics
Broadly, two types of road user characteristics are there
 Internal road user characteristics
 External road user characteristics
Internal road user characteristics are the internally related
characteristics of road users (human beings).
These are again of two types:
 Temporary internal road user characteristics
 Permanent road user characteristics

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1. Fatigue
Fatigue causes:
 Increased reaction time
 Ineffective judgment
power
 Drowsiness
All the above factors can
contribute to accidents.
2. Alcohol
Alcohol affects a person both
physically and mentally.
Alcohol causes:
 Reduced attention span
 Increased reaction time
 Ineffective judgment power
 Loss of control over one’s
own body

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3. Illness/Disabilities
This does not affect directly, but a person with a disability
tends to have more emotional reactions.
4. Anger
Anger develops rigid attitudes which can affect the road user
negatively.
5. Climate, season, and time
The above factors affect the judgment of a road user.

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 Permanent Road User Characteristics

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1. Vision
 Eye sight: The ability to perceive objects in average
illumination falls under eye sight. Cone of clear
vision is about 7-12º in the horizontal plane.
 Peripheral vision:- Though not very clear, objects
are visible beyond the cone of clear vision. This is
peripheral vision and the cone of peripheral vision in
horizontal degree is up to 160º.
 Eye movement: While traversing on road, the road
user has to shift his eyes for scanning. Different eye
movements are executed for this purpose.

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1. Vision
 Color vision: Color helps in the clear perception of objects.
 Glare vision and recovery: Extremely bright light that
blinds the vision is glare.
 Perception of time and space: This factor becomes
important in overtaking operations.

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2. Hearing: Hearing is not a significant factor in road
design.
3. Strength: It is required in vehicle maneuvering
operations.
4. Reaction time: It is the time lapsed in understanding
and adapting to a traffic situation.
5. Judgement power:
 It comes with experience and varies from person to
person.
 Judgment power is how a person reacts in a specific
situation.

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 External Road User Characteristics
Environmental factors are included in external road user
characteristics such as:
 facilities provided for traffic
 atmospheric conditions
 Locality
 land use
 altitude

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 Vehicular (Motor-vehicles) Characteristics
Design of dimensions and weight of vehicles is governed by
vehicular characteristics. Broadly, two types of vehicular
characteristics are there: –
 static vehicular characteristics
 dynamic vehicular characteristics

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 Vehicular Characteristics
Static Vehicular Characteristics
 Dimensions: Length, width, and height of a vehicle is
included in static characteristics.
 Weight: Weight of the vehicle is also an important
static vehicle characteristic.
 Maximum turning radius: It affects the design of the
mechanical widening of roads. When vehicles turn at
low speed the rear wheel presses the front wheel. This
difference between rear and front wheels is called off-
tracking. It is commonly known as mechanical
widening.

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Dynamic Vehicular Characteristics
 Speed of vehicle: Sight distance, super elevation, length
and radius of transition curves, the width of shoulders
and pavement, and design gradient are all affected by
the speed of the vehicle.
 Braking system of vehicle: Stopping distance and
distance between two consecutive vehicles is affected
by the braking system of the vehicle.
 Acceleration of vehicle: Intersection elements’ design is
affected by the acceleration of the vehicle.

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HIGHWAY CAPACITY
 Highway capacity is associated with traffic volume and
traffic density. Traffic volume is the number of vehicles
passing a given point on a roadway during a specified
time period. This is usually expressed as vehicles per
hour.

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HIGHWAY CAPACITY
 Traffic capacity is the maximum traffic density a road can
accommodate at a given speed without delay. Before the
actual capacity of a roadway can be determined, it
necessary to find the theoretical capacity. The formula
 N = 1760V divided by I is used for finding the theoretical
capacity for one lane of a roadway.
where,
 N- Theoretical traffic capacity, expressed in vehicles per hour.
 V- Constant vehicular speed, expressed in miles per hour.
 I- Intrevehicular lead, expressed in yards. (Intrevehicular lead
is defined as the distance from the front of one vehicle to the
front of the next vehicle in the traffic column)

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HIGHWAY CAPACITY
 Traffic density is the amount of traffic per unit of road length
(e.g., cars per day per kilometer) and can be useful for
comparing of the level of traffic between two or more areas.
 Hence, Highway capacity is associated with traffic volume
and traffic density. It refers to the hourly rate at a maximum
where vehicles can cross a point on a highway at a given
period. The traffic volume is usually conveyed in the form of
cars per hour. Traffic density is expressed as vehicles per
kilometer.
 The principle underlying the capacity analysis of road
segments is that speed decrease as flow increase. The
speed decrease with unit flow increase is small at low flows
but becomes greater as flows get higher. Near capacity, a
small increase in flows results in a large decrease in speed

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HIGHWAY CAPACITY
 An ideal road is one which has an excellent surface,
zero grade, zero curves and no interference such as
intersections. There are, however, no ideal roads.
 The theoretical capacity of a road is modified to
account for existing circumstances.
 Three factors determine the actual capacity of a road
physical characteristics of the road, characteristics of
the traffic using the road and traffic controls used on
the road.
 A good rule of thumb to use when estimating the
actual capacity of a road is to reduce the theoretical
capacity by 25 percent.

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HIGHWAY CAPACITY
The capacity of a roadway
can be improved in these
ways:
 Eliminate curb parking
or convert angle
parking to parallel
parking, if on-street
parking is essential.
 Eliminate left and right
turns.
 Properly define lanes.
 Relocate bus stops.
 Relocate objects near
edges of the roadway.

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Applications of Traffic Control Devices
 Traffic control devices direct, guide, and inform drivers
by offering visual or tactile indicators. Devices fall into
four main categories: signs; signals; road design and
marking; and barriers or channelizes.
 Road traffic control devices are markers, signs and
signal devices used to inform, guide and control traffic,
including pedestrians, motor vehicle drivers and
bicyclists.
 These devices are usually placed adjacent, over or
along the highways, roads, traffic facilities and other
public areas that require traffic control.

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 Traffic control devices direct, guide, and inform drivers
by offering visual or tactile indicators. Devices fall into
four main categories: signs; signals; road design and
marking; and barriers or channelizes.
 Road traffic control devices are markers, signs and
signal devices used to inform, guide and control traffic,
including pedestrians, motor vehicle drivers and
bicyclists.
 These devices are usually placed adjacent, over or
along the highways, roads, traffic facilities and other
public areas that require traffic control

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What are the 4 types of traffic control devices?
Public roads use a wide selection of traffic control tools
which can be adapted to smaller facilities. However, on
public roads, driver focus tends to be on signs and
signals. In smaller facilities, pavement markings and
barriers may take a greater share of the load.
 Types of Traffic Control Devices on public roads
 Traffic Signs.
 Traffic Signals.
 Markings on Road Surfaces.
 Creating Traffic Islands.

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 Traffic Signs. Road signs provide local information to
drivers. Made from reflective material in high-contrast
colors, they are highly visible in headlights at night.
Signs may use words and symbols to communicate
meaning.
Regulatory signs are the most important signs on the
road. They declare the accepted legal use of the
immediate public roadway. Intersection control
specifies proper behavior when roads meet signs like
stop or yield are essential for preventing conflict and
crashes.
Warning signs allow drivers to be aware of driving
hazards like animal crossings or twisting paths. They’re
installed for maximal safety.

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 Traffic Signs and signals .
Guiding or informational signs provide route and
amenity information to help drivers find their
destination. Route and exit information as well as those
marking rest stops, gas and food, and tourist
attractions all fit into this category.
Traffic signals in red, yellow, and green are universal
items in the traffic control landscape. To the standard
three lights may be added lane indicators and other
individual lane markings. Flashing lights, either in a
traditional signal or hanging alone, are common.
However, they can have variable meanings depending on
the region and the color. Steadily burning lights are often
used as warnings or mark hazards.

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 Road markings and road construction. Road design
offers another vocabulary for communicating with
drivers.
Road markings, like lines and arrows, are used to mark
correct legal usage of road surfaces. They include stop
lines, lane markers, turn lane arrows, and more. Road
markings like “sharrows,” showing that bikes and
motorized vehicles share the road, notify drivers about
unexpected traffic patterns.
Road construction is also involved in traffic control. Rumble
strips can mark lanes. When a car drifts over them, they alert
through sound and texture that the vehicle is no longer in its
lane. Rumble strips are often used in places where drivers
might miss a sharp bend in the road, or on long stretches
where a driver might fall asleep. Other road construction and
environmental design makes certain driving behaviors easier
than others. Speed humps and bumps, chicanes, neck
downs, curb extensions, roundabouts and more can
encourage proper driver behavior.

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 Barriers and channelizes. Barriers and channelizes also
control traffic, warn against hazards, and mitigate
accidents. There are many types.
Traffic delimiters and cones are often placed temporarily to
provide warning around hazards or work zones..
Highway barriers, like standard Jersey barriers, help
prevent head-on collisions and mark lanes. They can
sometimes mitigate or prevent shallow angle accidents by
returning a car to the roadway. Highway barriers may be gated
or non-gated, either by cushioning an impact of a car but
letting it through or by stopping it all together.
Channelizes and road barriers, whether barrels, curbs, or
bollards/posts, are more permanent than traffic delimiters or cones
though some may be removable for multi-access spaces. Flexible, crash-
rated, or security posts are all used to guide traffic away from certain
areas. The crash-rated and security types provide impact protection that
is very effective at stopping head on or deep angle crashes

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 All the vehicles do not keep moving along the roadway
during the entire 24 hours of the day; they have to stop
or park at the desired locations for different duration’s.
 In cities the problem of parking vehicles is becoming
more and more acute day by day.
 When vehicles are parked on the road side even for a
short while. Therefore, there is restriction to other
vehicles passing by, resulting in congestion and
accidents.
 In shopping centers, public places and localities with
offices there is a shortage of parking facilities.
 Proper planning and design of parking facilities is
essential in cities and large towns.
Design of Parking Facility

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Parking facilities may be broadly divided into two types:
 On-street or kerb parking: In this type of parking,
vehicles are park along the kerb which may be
designed for parking. Kerb parking is quite convenient
for those who find suitable space to park their vehicles
near the place they wish. But for others who do not find
a parking space it is a problem. Kerb parking facility
may be either unrestricted or restricted type. The
restricted kerb parking may either be controlled by
police or by parking meters. Therefore, a specified
parking fee is collected from those who park their
vehicles for a certain duration of parking time. Different
patterns of kerb parking are ‘parallel parking‘ and
‘angle parking‘

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 Parallel parking: It needs less roadway width, but
number of vehicles that can be parked per unit length
of road is least. Parallel parking is generally prefer
when the width of kerb parking space and the width of
the street are limit.

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 Angle parking: Angle parking may be at angles 30, 60
or 90 degrees. The width of the roadway required for
parking; also the width required for parking and
unparking manoeuvres increase with increase in
parking angle up to maximum 90° angle. Angle parking
accommodates more vehicles per unit length of kerb;
maximum number of vehicles that can be parked per
unit length of the kerb is with right angle parking. Angle
parking is more convenient to the drivers for the
parking and unparking manoeuvres than the parallel
parking; however these cause much more obstruction
to the through traffic resulting in more accidents than
the parallel parking.

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 Angle parking:

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 Angle parking:

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 Off-street parking: At locations where the parking demand is
high and kerb parking cannot be permitting in view of traffic
congestion, off-street parking facilities are providing at the
nearest locations depending on the availability of space for
this purpose. When a parking facility is providing at a separate
place away from the roadside or kerb, it is termed as ‘off-
street parking’.
 The main advantage of this method is that there is no
unnecessary increase in congestion, delay and hindrance to
moving traffic due to on street parking on the already
congested roads. T
 The main drawback is, some of the vehicle users will have to
walk a greater distance after parking the vehicle at the off-
street parking facility. It is also not possible to provide the off-
street parking facility at very close intervals especially in
business centers of a city.

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Types of off-street parking: Two basic types of off-street parking
facilities are, ‘surface parking lots’ and ‘multi-floor parking
garages’. Both in the parking lots and the garages, the basic
traffic operations consist of five steps namely,
 Entrance
 Acceptance
 Storage
 Delivery
 Exit.
Hence some definite space is requiring in front of the parking lot
or garage for vehicles during entrance acceptance and also for
exit operations. This space providing is termed as ‘reservoir
area’, the size of which depends on the average rate of arrival of
vehicles to be park during peak hour

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 Surface parking lots: Surface parking
lots may be convenient where
sufficient space is available at
comparatively low cost. When the
parking of vehicles is doing by
owners or drivers of the cars, the
method is termed “self parking
system’. If the vehicle is left by the
driver at the entrance space and
again collecting from there, the
parking and delivering operations
being carried out by attendants, it is
termed ‘attendant parking system’.
Most important advantage of
attendant parking is less space
requiring to store and manoeuvres
the same number of cars.

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 Multi-storey parking garages: are
restored to when the floor space
available for the parking garage is
less and is very costly. It is
possible to construct multi-storey
garages to park a large number of
cars at a time. The garages can be
above the ground or below the
ground or an integral of both. It is
necessary to provide the inter-floor
travel facility for the vehicles, which
may be either by ‘elevators’ or by
‘ramps’. In mechanized garages
the elevator may be designed to
move both in vertical and in
horizontal directions to carry and
place the vehicle in the appropriate
parking stall and to deliver it back

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 Multi-storey parking garages: are
restored to when the floor space
available for the parking garage is
less and is very costly. It is
possible to construct multi-storey
garages to park a large number of
cars at a time. The garages can be
above the ground or below the
ground or an integral of both. It is
necessary to provide the inter-floor
travel facility for the vehicles, which
may be either by ‘elevators’ or by
‘ramps’. In mechanized garages
the elevator may be designed to
move both in vertical and in
horizontal directions to carry and
place the vehicle in the appropriate
parking stall and to deliver it back
Traffic Engineering Studies

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