the attainment of independence, Nigeria has witnessed rapid economic and social
development, which has open up the need for travelling between cities which led
to increase in the need for good and safe road.Highway is any public road or other public way on land; the term exists in
distinction to waterway also can said to be
high-speed roads designed to connect major cities. A highway is a major road
for any form of motor transport which vehicles and the public in general may
lawfully pass without license. A road on the other hand is a way for vehicle
and other types of traffic (human or animal) which may or may not be lawfully
usable to the public at large. Highways are vitally important to a country’s
economic development. The construction of a high quality road network directly
increases a nation’s economic output by reducing journey times and costs,
making a region more attractive economically. The actual construction process
will have the added effect of stimulating the construction market. Roads could
be considered as a cause and the consequence of civilization, as they both
precede and follow it.
BACKGROUND OF ROAD
The need for road construction came up with the invention of
the wheel some 5000 years ago. Prior to this invention, people and
transportation beast simply moved on tracks which were only wide enough for
their comfort. With the invention of the wheel, there was the need for
improvement on the existing tacks to provide firmer and wider surfaces with
better riding qualities to accommodate higher volume of traffic. These
improvements were carried out in order to increase the safety and speed of
conveying people and goods from one place to another for social and commercial
Road transport is one of the most common mode of transport.
Roads in the form of track ways, human pathways etc. were used even from the
pre-historic times. Since then many experiments were going on to make the
riding safe and comfort. Thus road construction became an inseparable part of
many civilizations and empires. The need
for road construction came up with the invention of the wheel some decades ago.
Prior to this invention, people and transportation beast simply moved on tracks
which were only wide enough for their comfort. With the invention of the wheel,
there was the need for improvement on the existing tacks to provide firmer and
wider surfaces with better riding qualities to accommodate higher volume of
traffic. These improvements were carried out in order to increase the safety
and speed of conveying people and goods from one place to another for social
and commercial purposes.
There are many different types of highways. Highways differ
primarily in the amount of access control they have and, therefore, in the
amount of traffic they are designed to carry. Highway with fully controlled
access can handle the most traffic and are built to the highest construction
standards. Inter-state highways. Vehicles that enter or exit these types of
highway can do so only at certain points along the highway, generally by using
special entrance and exit ramps. The ramps allow vehicle to access the road
without disturbing the flow of traffic. Incoming vehicles must merge with
flowing traffic, and vehicles leaving the highway use exit ramps that guide
them off the highway without blocking the traffic behind. Intersections with
other roads are avoided by using either bridge known as overpasses to carry one
roadway under another. Finished strips called shoulders on the edges of
highways allow drivers of disabled vehicles to make repairs or await assistance
without blocking traffic.
THE PURPOSE OF
HIGHWAYThe purpose of the highway is to provide a means of reducing
the stress or pressure due to a wheel load to the minimum value which the
ground under the structure can support. This is why materials of the highest
strength are used for the surface. Other purposes of highway are listed below:
It provide a skid resistance surface
It provide wider riding surface to accommodate
anticipated traffic volume
It provide a firmer riding surface ands
It provide a smooth riding surface
It provide efficient and convenient movement of
people and goods from one place to another.The intensity of the stress is
greatest at the surface of the road and it is distributed in a pyramid from
down the depth of the formation. As long as the stress reaching the sub grade
does not exceed the resistance put forth by the sub grade, there will be no
distortion or damage to the road surface.
Geometric design is defined as the design or proportioning
of the visible elements of the street or highway. The geometry of the roadway
is of central importance since it provides the framework for the design of
other highway elements. In addition, the geometric design establishes the basic
nature and quality of the vehicle path, which has a primary effect upon the
overall safety characteristics of the street or highway.
The design of roadway geometry must be conducted in close
coordination with other design elements. These other elements include: pavement
design, roadway lighting, traffic control devices, transit, drainage, and
structural design. The design should consider safe roadside clear zones,
bicycle and pedestrian safety accommodation, emergency response, and
The geometric design of highways deals with the dimensions
and layout of visible features like of the highway. The emphasis of the
geometric design is to address the requirement of the driver and the vehicle
such as safety, comfort, efficiency, etc. The features normally considered are
the cross section elements, sight distance consideration, horizontal curvature,
gradients, and intersection. The design of these features is to a great extend
influenced by driver behavior and psychology, vehicle characteristics, traffic
characteristics such as speed and volume. Proper geometric design will help in
the reduction of accidents and their severity. Therefore, the objective of
geometric design is to provide optimum efficiency in traffic operation and
maximum safety at reasonable cost. The planning cannot be done stage wise like
that of a pavement, but has to be done well in advance. The main components
that will be discussed are:
CapacityThe safety characteristics of the design
should be given primary consideration. The initial establishment of sufficient
right of way and adequate horizontal and vertical alignment is not only
essential from a safety standpoint, but also necessary to allow future
upgrading and expansion without exorbitant expenditure of highway funds.
1.4 CLASSIFICATION OF ROADS
Roads can be classified in many ways. The classification
based on speed and accessibility is the most generic one. Note: As the
accessibility of road increases, the speed reduces. Accordingly, the roads can
classify as follows in the order of increased accessibility and reduced speeds.
Freeways are access controlled divided highways. Most freeways are four lanes,
two lanes each direction, but many freeways widen to incorporate more lanes as
they enter urban areas. Access is controlled through the use of interchanges,
and the type of interchange depends upon the kind of intersecting road way
(rural roads, another freeway etc.)
They are superior type of highways and are designed for high speeds (120 km/hr.
is common), high traffic volume and safety. They are generally provided with
grade separations at intersections. Parking, loading and unloading of goods and
pedestrian traffic is not allowed on expressways.
They represent the superior type of roads in the country. Highways are of two
types – rural highways and urban highways. Rural highways are those passing
through rural areas (villages) and urban highways are those passing through
large cities and towns, i.e. Urban areas.
It is a general term denoting a street primarily meant for through traffic usually on a continuous route. They
are generally divided highways with fully or partially controlled access.
Parking, loading and unloading activities are usually restricted and regulated.
Pedestrians are allowed to cross only at intersections/designated pedestrian
streets: A local street is the one which is primarily intended for access
to residence, business or abutting property. It does not normally carry large
volume of traffic and also it allows unrestricted parking and pedestrian
streets: These are streets intended for collecting and distributing traffic
to and from local streets and also for providing access to arterial streets.
Normally full access is provided on these streets. There are few parking
restrictions except during peak hours.
1.5 BACKGROUND AND PURPOSE
Highway geometry should be designed for vehicle traffic
safety and efficiency, particularly on the trunk roads or Expressways on which
traffic function must be most important. Though the design policy was
established, the prerequisites of design have been imaginary or extremely
limited. For example, minimum radius of horizontal curve is defined with design
speed, super elevation and side slip friction factor. The actual operating
speed must correspond to something speed, but it did not work well to be used
for design purpose of road geometry, or did not calibrated enough because of
the difficulty of data acquisition. Such an estimation model should have a
feature including driver’s perception and behavior.
1.6 AIM AND OBJECTIVES OF THE STUDY
The aim of the study is to perform the geometric design of a
selected case study road.
And comparison between Manual and Automated design.
The objectives required to achieve the above aim include:
Design of all vertical alignment components
Design of all horizontal alignment components
Comprehensive plan and profile detailing of the
case study road.1.7 SCOPE
The scope of this study covers the geometric design of
highway at Anka road, bukkuyum L.G.A Zamfara State. Using manual design and
comparing with automated design.
1.8 OUTLINE OF STUDY
For a proper understanding of this project report it has
been divided into five chapters.
Chapter one introduced the project; chapter two discusses
the relevant literature in respect to this project. Chapter three contains the
design methods of highway designed detail. Chapter four contains the result and
analysis and finally recommendations and conclusion based on findings is shown
in chapter five.