1. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
1
CAUSES OF HIGHWAY FAILURE IN NIGERIA
Abstract
Road failure is a major problem in most of developing countries and even the developed ones, in
view of high cost of maintenance and reconstruction. This paper takes a critical look at this
common phenomenon. The paper looks at functional failure of flexible pavement by reviewing
related literature such as journals and textbooks, and find out that moisture penetration,
inadequate drainages system and lack of in depth technical information during design stages are
few reasons responsible for road defects, which if left unchecked could result to road failure.
Key words: Failure, Pavement, Road, drainage. Flexible, Rigid.
INTRODUCTION
. A flexible pavement typically consists of three or four layers. For a four layers flexible
pavement, there is a surface course, base course, sub-base constructed over a compacted, and
natural soil subgrade. When building a three layer flexible pavement, the sub-base layer is not
used and the course is placed directly on the natural subgrade (CORD, 2013). Figure one shows
the layers of flexible pavement.
Figure 1: Layers of flexible pavement
Rigid pavements are generally used in constructing airport and major highways, such as those in
the interstate highway system. In addition, they commonly served as heavy-duty industrial floor
slabs, port and harbor yard pavements, and heavy-vehicle Park or terminal pavements. Like
flexible pavements, highway pavements are designed as all-weather, long lasting structures to
serve modern day high-speed traffic. Offering high quality riding surfaces for safe vehicular

2. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
2
travel, they function as structural layers to distribute vehicular wheel loads in such a manner that
the induced stresses transmitted to the subgrade soil are of acceptable magnitudes.
Figure 2: Layers of rigid pavement
The catalogue of road defect (CORD, 2013) refers to road defects as the visible evidence of an
undesirable condition in the pavement affecting serviceability, structural condition or
appearance. The aim of this paper is to examine the cause of highway failure in Nigeria.
LITERATURE REVIEW
In its annual report the department for transport (DFT, 2013) describe drainage as an essential
part of road way maintenance, that the major reason for pavement failure is percolation of
moisture into the base material, this can occur in many ways; cracks on the road surface create
access for moisture penetration, other ways are underground pipe water, through road edge
which has no shoulder and stagnant water on road surface. Before these defects are fully
explained, it will be interesting to know the functions of layers that make up flexible pavement.
The following are the functions of flexible pavement layers.
Functions of Flexible Pavement Layers
According to Okigbo (2012) a flexible pavement is made up of different processed and
compacted material to form various layers, except the subgrade which is natural layer. The layers
are;
 Surface course
 Binder course
 Base course
 Sub-base
 Capping layer

3. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
3
 Subgrade
Figure 5: A section of flexible pavement.
These layers are expected to exhibit reasonable high dynamic stiffness values. Khweir and
Fordyce (2003) argue that it is a misjudgment to assume that all the pavement layers work as a
monolitich structure, because pavement can be affected by interface problem. They further stress
that a pavement can fail even if exposed to traffic volume less than design values, each layers
showing very high dynamic stiffness modulus values and ability to resist deformation and
fatigue. Properties of material selected and methods of construction can reduce bonding of the
interface.
Sub-base and subgrade are the under laying layers of road pavement, and should withstand all
the traffic loading stresses distributed by the pavement as part of its function, without deforming.
Over stressing and consistent level of critical tensile stress could cause road base failure. Base
layer of pavement is one of the major load bearer, road base cannot be discuss without
mentioning sub-grade and sub-base, this is because they perform almost the same functions
under road pavement, damage to one layer is damage to all layers. Momoh, Akinwumi and
Olorunfemi (2008) assert that, adequate knowledge of sub-surface conditions below the highway
route as the basis for proper road design. They further stressed that geological factor should be
considered as one of reasons responsible for road failure, because all roads are constructed on
geology.
”The department of transport’s engineering intelligence division, now superseded
by the pavement section of the Highways Agency (HA), commissioned a risk
analysis of entire road pavement design and construction process which
concluded that the greatest single area of risk was in assessing the design strength

4. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
4
of the subgrade. This is usually expressed as its California Bearing Ratio
(commonly called the CBR) since the California State Highways Department
introduced the test into its own pavement design procedures in the 1930s. The
current UK CBR tests are described in BS1377: part 4² for testing in the
laboratory and BS1377: part 9³ for testing insitu” (Hunter and Robert, 2000, pp
511).
The roles of side drains cannot be over emphasis, this point is further buttress by McRobert, et al
(2000) the most essential part of road design is drainage and it must be considered in
construction and maintenance of all roads, unsealed roads included. It is a fact that road
deterioration is as a result of increase in water content of granular materials. One of the defects in
rigid pavement (concrete) is caused by change in temperature Diefenderfer, et al (2002) there are
at least six defects associated with excess water; reduction of shear strength of unbound
materials, differential swelling on expansive subgrade soils, movement of unbounded fines in
flexible pavement base and sub base layers, pumping of fines and durability cracking in rigid
pavements, frost heave and thaw weakening, and stripping of asphalt in flexible pavement. Poor
drainage will reduce the life of the pavement and have serious environmental impacts if left
unchecked
Common Defects on Nigeria Roads
According to Okigbo, (2012) the following are the common defects on Nigeria roads, and have
caused fatal accidents and loose of lives and properties:
 Insufficient road shoulder
 lack of equal lanes,
 Poor road signs
 Damaged stop lights
 Community negligence and bad construction
He also indicates that the definition of “road defects” includes any part of a road, highway, or
construction site that does not meet the regulations for a safe road. However, Nordengen and
Oberholtzer, 2006 describe volume of traffic and size as a major contributor to road safety and
conditions. Road deterioration is very common in developing countries, keeping roads in good
condition is the most cost-effective way to safe Nigeria roads.
Fatigue is one of the causes of pavement failures as highlighted by Oguara 2010. Fatigue occurs
as a result of consistence loading of materials, the amount of loads apply determine the bending
of the pavement. A road open to high traffic loads must be properly design compare to one with
light traffic load. Spring time has frequent record of paved road flexing, due to material
saturation and deformation. Upward seepage of water due to increase in level of ground water as
a result of capillary suction is responsible for lateral flow of water to pavement edges and side
ditches (Rokade, Agarwa and Shrivastava 2012).

5. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
5
In my opinion, the major contributing factor in roads failure in Nigeria is community negligence
and lack of maintenance. This is because all the states in Nigeria depend on the federal
government allocation, more often than not, the allocation is insufficient to take care of all the
infrastructure within the states. Even where these roads are maintained, dumping of refuse into
road side drainages which could lead to blockage of the drainages and eventually over flooding
of the road.
Weather Condition
This could be a source of another problem for road pavement as highlighted by Hunter and
Robert (2000), weather conditions, wet or dry affect the strength of subgrade or subsoil, sub-base
must be constructed on a dry subgrade, adequate drainage is needed to prevent the subgrade from
being soaked, which could lead to strength reduction. Rokade, Agarwa and Shrivastava (2012) to
prevent pavement system from premature failure, means of excluding moisture or dampness
from the pavement should be included during design processes. The excavated subgrade
materials is subjected to changes depending on the conditions it is exposed to during its life time.
Defective drainage, inadequate maintenance of a well-constructed drainage system, poorly
backfilled (mostly caused by repair on utilities) are some of the factors responsible for failure of
a well-constructed pavement layers. Other factor responsible for pavement defects are further
discovered by Rokade, Agarwa and Shrivastava (2012) are pumping action, loss of support and
rutting, they highlighted that percolation of moisture into unsaturated pavement layers is mostly
caused by rainfall. Pavement defects such as; joints, cracks, and shoulder edges are the loop-
holes through which moisture penetrate.
Experience has shown that a pavement may last for more than hundred years if all defects could
be prevented from occurring. (ASCE, 2009) referred to road performance as the ability of the
pavement to satisfy environmental and traffic demands. Furthermore, to prevent additional
reconstruction cost to road users or DBFO (design, Build, Finance and Operate), it will be a good
practice for designer to have it in mind that construction of new projects and reconstruction of
existing roads, the sub-base and any capping which support the road base, should be designed on
the fact that, the strength of subgrade will be reduced to its soaked value at some stages in its life
time. However, it is not common for a well- designed road base to fail in its service life. This can
only occur if the amount of ground water discovered was not anticipated during design stage.
However, the function of effective drainage system cannot be over emphasis. “Drainage is an
important parameters which affects the highways pavement performance. Excessive water
content in the pavement base, sub-base, and subgrade soil can cause early distress and lead to a
structural or functional failure” (Gurjar, J, Agarwal, P.K, and Sharma, M.K, 2013). Asma, T.,
Suda, I, and Gari, M. (2011) suggested that carrying out preventive maintenance on flexible
pavement is the lasting solution to reducing deterioration of well-constructed roads and
enhancing its life span.
However, Rojer, (2003) argue that a road subjected to high traffic loads will deteriorate inform
of cracking mostly on the surface of the pavement and not necessarily deep down the structure, a

6. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
6
well-constructed road will be durable if any signs of deterioration inform of cracking is well
maintained before it affects the structural capacity of the pavement. He further categorize
pavement deterioration into four phases. Phase one, when the new/strengthened pavement
reaching stability, at which point its load spreading ability is still improving. Phase two, when
load spreading ability is quite even and the rate of structural deterioration can be calculated with
some confidence. Phase three, at this stage, deterioration becomes less predictable and strength
may decrease gradually or even rapidly. This is the investigatory phase. A pavement entering this
phase should be monitored in order to ascertain if any remedial action is required to be carried
out on it. Residual life is defined as the period of time before a pavement reaches this phase.
Phase four, here the pavement has deteriorated to failure. Strengthening can only be achieved by
total reconstruction. This phase can last quite a number of years, with maintenance becoming
necessary with increasing frequency until the point is reached where the cost associated with this
treatment make reconstruction the cheaper option (Rojer, 2003).
Cracks in rigid pavement can be increased by stress induced at the edge or corner of the slabs. A
tin crack which normally occur when concrete is drying is often negligible, but any crack which
is (>0.15cm) will reduce bond and the interlocking strength of the aggregate by allowing
moisture penetration into the structure. Any crack more than 0.5mm will reduce aggregate
bonding. Common cracks in flexible pavement are shown below in figure 3 and 4.

7. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
7
Figure 3. Longitudinal crack on flexible pavement. (Source www.googleimage.com;
2008)

8. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
8
Figure 4. Alligator crack on flexible pavement.( Source www.google.com; 2008)
Occurrence of one of the following condition in an unreinforced concrete means the concrete has
failed.
 An average or big crack crossing the bay of the slab transversely or longitudinally.
 An average longitudinal and average transverse crack intersecting, both exceeding
200mm in length and originating from the edge of the pavement.
 A big crack at the corner, more than 200mm in radius, centered at the corner.
According to Ette (2010) an- inter- urban roads study was commissioned in 1998/99, the study
comprised roads with traffic of more than 30 vehicles/day covering total distance of 53,000km
except urban roads. The result is on the table 1.

9. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
9
Table 1; Condition of National Road Network in Nigeria 1999
CATEGORY INTERNATIONAL PERCENTAGE OF
ROUGHNESS INDEX NETWORK
Good <3.5m/km 27%
Fair 3.5-4.5m/km 38%
Poor >4.5m/km 35%
Source; Ette (2010) Book of proceedings 19th Engineering Assembly, page 18.
CLASSIFICATION OF NIGERIAN ROADS
Roads in Nigeria are spread over the thirty six states and the nation capital, it consists of more
than 32,000 km of federal roads, more than 30,000 km of state roads and more than 130,000 km
of local government roads.
TABLE 2; ROAD OWNERSHIP IN NIGERIA SHOWN BY DISTANCE COVERED.
FEDERAL
ROADS (KM)
STATE ROADS
(KM)
LOCAL
GOVERNMENT
ROADS (KM)
TOTAL PERCENTAGE
Paved main
roads
26, 500 10, 400 36,900 19%
Unpaved main
roads
5,600 20,100 25,700 13%
Urban roads 21,900 21,900 11%
Main rural roads 72,800 72,800 38%
Village access
roads
35,900 35,900 19%
TOATL 32,IOO 30,500 130,600 193,200 100%
Percentage 17% 16% 67% 100%
Source; okigbo (2012)
The federal ministry of work’s publication in June 2011 indicate that, federal roads can be
divided into federal trunk ‘A’ and federal trunk ‘F’ Federal trunk ‘A’ are roads including bridges
that are under the care and maintenance of federal ministry of works, while federal trunk ‘B’ are

10. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
10
those states roads taken over by the federal government for upgrading to highway standards.
State roads are referred as trunk ‘B’, these are road under the care and maintenance of state
government, while trunk ‘C’ roads belong to local governments. The length of federal roads in
each state of federation and the nation capital is indicated in the table three below.
TABLE; 3. LENGTH OF FEDERAL ROADS IN THE VARIUOS STATES OF NIGERIA IN KILOMETERS.
North West/ km North East/ Km North Cent km South west Km South East Km South South km
Jigawa 757 Adamawa 1379 Benue 1632 Ekiti 376 Abia 638 Akwaibom 608
Kaduna 1730 Bauchi 1335 Kogi 1173 Lagos 625 Anambra 746 Bayelsa 168
Kano 2098 Borno 2027 Kwara 1044 Ogun 1185 Ebonyi 609 Cross River1245
Katsins 842 Gombe 434 Nasarawa 900 Ondo 900 Enugu 959 Delta 1068
Kebbi 862 Taraba 1634 Niger 2165 Osun 672 Imo 680 Edo 898
Sokoto 584 Yola 877 Plateau 936 Oyo 1157 Rivers 708
Zamfara 1040 FCT 200
Source; Okigbo,(2012).
The causes of road failure are not limited to those identified in this paper, further study can be
carry out on other causes of road failure such as effects of temperature on the bonding of asphalt
and viscosity of bitumen in road construction.

11. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
11
Conclusion
Road pavement can last more than hundred years. Moisture penetration, rise in ground water
level, seepage due to capillary action, insufficient drainage system are responsible for premature
pavement failure. Pavement serviceability life can be enhanced and cost of maintenance and
reconstruction reduced, if external conditions such as; whether (rain), geological formation of the
site (type of soil) and environmental condition (surface water) could be critically considered
during design, so that provision of adequate drainage will be made for surface and sub-surface
water.

12. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
12
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13. ALIYU HAMZA
SCHOOL OFENGINEERING ANDENVIRONMENTALSTUDIES
ABDU GUSAU POLYTECHNICTALATA MAFARA ZAMFARA STATE.
13
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