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Safety on Nigeria roads has become a thing of concern in recent times. This is as a result of numerous carnages that have characterized with Nigeria roads. This loss of lives and properties have been attributed to many factors including poor road design and defective construction practice. A road that is poorly designed, is in no doubt a threat to the safety of the road users.

In this paper, therefore the way in which highway design and construction practice impacts on the safety of Nigeria roads, was discussed.


In doing that, efforts were made to look at the International Standard of highway design and construction practice, with the view of comparing them with the happenings in Nigeria. As a matter of fact, the road geometrical elements were discussed in detail. The Cross section elements such as (pavement width, formation width) site distance; horizontal and vertical alignment details; intersection elements; road furniture and factors that affect geometric design, were also discussed.


Project Topics

For this study, some Nigerian roads within the area of study were investigated. The roads investigated were selected based on the Road Traffic Crash (RTC) gotten from the Federal road safety corps (FRSC). These roads selected are those that record high RTC. Also, along these routes, some places were identified as black spots, which are crash prone areas. Some of these routes and black spot were critically examined and findings were made. Pictures of some of the black spots were shown in this paper.

Questionnaires and interviews were also employed in the course of this paper.




Tile Page                                                                                                                                 i

Abstract                                                                                                                                  ii

Dedication                                                                                                                              iii

Acknowledgement                                                                                                                  iv

Table of Content                                                                                                                     v

List of Tables                                                                                                                          viii

List of Figures                                                                                                                         ix

List of Plates                                                                                                                           x

List of symbols                                                                                                                       xii



  • Background 1
  • Statement of the Problem 8
  • Significance of the study 8
  • Scope of the Study 9
  • Objectives of Study 10
  • Research questions 11
  • Delimitation 11



2.1       Background                                                                                                                12

2.2       Geometric Design                                                                                                       13

2.3       Site Distance or Visibility                                                                                           29

2.4       Alignment                                                                                                                   36

2.5       Intersection                                                                                                                 54

2.6       Road Furniture                                                                                                            65

2.7       Design Controls and Criteria                                                                                      70

2.7.1    Topography                                                                                                                 71

2.7.2    Other Factors                                                                                                              71

2.7.3    Classification of Roads                                                                                               75




3.1       Data Collection and sources of Data                                                                          77

3.1.1    Primary Sources                                                                                                          77

3.1.2    Secondary Sources                                                                                                      80

3.2       Method of Data Collection                                                                                         81

3.3       Method of Data Analysis                                                                                           82



4.1       Presentation of Data                                                                                                   83

4.2       Road Traffic Crash (RTC) Data                                                                                 83

4.3       Scoring of the Road Safety Design Variables along the route and black spots         92

4.4       A scoring Model for Decision Analysis                                                                      93

4.5       Model Validation by Road Safety Experts                                                                94

4.6       Study of Udi –Four Conner Road                                                                              100

4.7       Questionnaire Data Presentation                                                                                108




Discussion, Conclusion and Recommendation

5.1       Discussion of Findings                                                                                               114

5.2       Road Design and defect                                                                                             119

5.3       Conclusion                                                                                                                  122

5.4       Recommendation                                                                                                        123







The road is an important infrastructure in the world today.  It originated for economic reasons, related to the need to move food and other goods from one point to another. Early transportation focused on moving food from a hunt or a harvest to the places where people lived. Trails evolved from prehistoric animal paths, along which humans carried or dragged their loads. As humans learned to domesticate animals, they transferred their loads to pack animals, such as horses, mules, camels, llamas, elephants, and dogs.

The need for roads has continued to rise particularly roads that are safer and easy to use. The advent of motor vehicle warranted the need to make the road more motorable. Man in his artistry began to put things on the road for easy passage of the road users. Things like cobblestone, concrete and asphalt were introduced in road construction [31]. Cobblestone was the first to be introduced. The use of cobblestone makes the road more motorable. As this goes on more vehicles were introduced in the road.

As more vehicles were constructed and introduced on the road, road accidents started occurring. In 1896 in Great Britain two deaths were registered [31]. One was registered in the United States in 1899. The one of 1896 actually happened in UK of which the person that was hit died. The unfortunate incidence involved a 44-year-old woman named Bridget Driscoll who was hit by a car as she walked to a dancing display at London’s Crystal Palace in August 1896. The driver of the vehicle was Arthur Edsell, a 20-year-old who had been driving for only three weeks, and it was later discovered that he had been travelling at more than twice the 4mph speed limit when the fatal accident occurred.[31] This became a concern to road users (i.e. man).


From records, more lives are being lost on roads than in any other areas [30]. Since the invention of the motor vehicle over a century ago, it is estimated that about 30 million people have been killed in road crashes worldwide [30]. From the world health organization, approximately 1.3 million people die each year on the world’s roads, and between 20 and 50 million sustain non-fatal injuries. The Global status report on road safety is the first broad assessment of the road safety situation in 178 countries, using data drawn from a standardized survey. The results show that road traffic injuries remain an important public health problem, particularly for low-income and middle-income countries. World Health Organization (WHO) predicts that road traffic injuries will rise to become the fifth leading cause of death by 2030 [3]. Pedestrians, cyclists and motorcyclists make up almost half of those killed on the roads, highlighting the need for these road users to be given more attention in road safety programmes. The results suggest that in many countries road safety laws need to be made more comprehensive while enforcement should be strengthened. The Global status report on road safety results clearly show that significantly more action is needed to make the world’s roads safer. This is one of the reasons the United Nations (UN) in 2010, came up with the Decade for Action on road safety, thereby enjoining all nations of the world to be committed in this campaign of the “Decade of Action on road safety”. The move was as a result of good data collection in line with road good practice on road safety.

The main objective of good road safety practice is to ensure that more lives are saved on our roads. However in making the road safer, – the causes of road accident have to be identified.

Due to the absence of full functioning railway and water transport system in Nigeria today, about 90% of passengers and goods traffic are carried by road [5]. This, as a matter of fact, increased the number of road traffic accidents. In Nigeria, between 2002 and 2008, a total of forty thousand and seven (40,007) persons were killed while 136,068 suffered different degrees of injuries on Nigeria roads. This gives a fatality rate of 28 persons per 100,000 population using the last census figures. In 2008 alone, the number of people killed in motor vehicle crashes totaled 6,661.  That is an average of 18 persons every day.  During that same year of 2008, another 27,980 people sustained injuries of varying degrees in road traffic crashes, just a part of the damage inflicted by the annual total of 11,341 crashes [39]. When considered against the backdrop of the obvious under-reporting and increasing vehicle and human traffic interaction, these figures become sources of great concern, not only to the government, but also to concerned agencies in road safety.

The causes of these road accidents and hence deaths, have been a problem that is being addressed over the years. As a result this problem, there have been several studies on the causes of road crashes. Over the years, many causes have been identified. Road Accident Immunity Delusion Syndrome (RAIDS) is one of the causes of Road Traffic Crash (RTC) [5]. This is a situation where motorist in an enclosure feel protected and often assume absolute immunity from accidents. This term is coined by the Federal Road Safety Corps (FRSC) of Nigeria. RAIDS is also as a result of the reliance on charms for protection against accident. This is another symptoms often associated with nations that are at the religious stage of their development.

Other causes like speeding, drinking and driving, cell phone distraction, faulty vehicles, drugs, weather, driver recklessness etc, has also been identified as causes of road accident. Most faulty decisions that result in motor vehicle crashes are attributed to ignorance of traffic regulations and procedure. In other words ignorance of traffic regulations and procedures is a contributing factor to road accident. Ann ill-informed road user portends a crash waiting to happen, often with fatal consequences.

Sometimes some crashes are intended. It is called ‘staged crash’. It may happen in a situation where someone crashes a vehicle in order to submit lucrative claims to an insurance company. “In the 1990s, criminals recruited Latin immigrants to deliberately crash cars, usually by cutting in front of another car and slamming on the brakes. It was an illegal and risky job, and they were typically paid only $100. Jose Luis Lopez Perez, a staged crash driver, died after one of such maneuver, leading to an investigation that uncovered the increasing frequency of this type of crash.” [29]

Apart from the above, there are other causes of road accident. A new factor that is causing road accident which is now gaining momentum is the road itself. Many roads are now regarded as death traps. Poorly designed and/or badly constructed road, bad materials used for construction, poor intersection, etc, are contributing factors to the defects on the road, that makes the road bad [24].

According to recent Arab news [25], defects in road design is an important cause of traffic accident. For example, there are depressions in roads, where water collects with no system to drain it away. There are roads with no other way for cars to exit, in event of an emergency. Some roads are asphalted while others are not. Some roads are well maintained, but most are not. Roundabouts are also a problem in many streets. There are many small gaps in roadways which cause accidents when cars travel over them. An absence of sidewalk and too many crossroads with no signs indicating which vehicle has priority, cause a number of accidents. All of these factors contribute to high number of traffic accident.

Anytime an accident occurs, it is easily blamed on the driver. But it is not every automobile accident that is caused by driver’s error such as speeding, texting (i.e. sending messages in mobile phones), drinking, inattentions etc. Often times the roads themselves are to blame. Pavement edge drop-offs as shown in fig 1.1a and 1.1b, bad curves, potholes, poor slope construction, and the like, can all cause road accidents resulting into serious injuries and even death. Pavement edge drop-off seems to cause some of the worst accidents. When a car tire drops off one of these edges, a ‘bounce’ can occur, causing the driver to over correct and often times lose control.


Plate.1.1a Pavement edge drop-off located along Enugu 9th mile road Nigeria

Source: Field work


Plate 1.1b: Pavement edge drop-off located along Enugu 9th mile road Nigeria

Source: Field work


Potholes (shown in Fig. 1.2) on its own, have also contributed much in road accidents. In Nigeria, this is common as some of the accidents occur mostly when a driver tries avoiding a pothole, thereby either hitting another vehicle or losing control.

Plate1.2: Pothole on a road located along Enugu- Onitsha old road Nigeria

Source: Field work

Most of the potholes can be linked to unstable subgrade. Normally, if unstable subgrade is encountered (based on the defined CBR threshold value), it should be cut out so as to reach a firm foundation and then replaced with an adequately compacted soil, or aggregate materials (including stone bases), otherwise it should be stabilized by lime, cement, or the use of geotextile to produce a stable platform for both construction equipment and eventual road users on completion [24]. If not done, potholes will manifest on the road surfaces, thereby contributing to the road hazards.

Inadequate or absence of road furniture, has also contributed significantly to road accident. Wet surfaces also contribute to accidents. In such situations, it happens in the blink of an eye; one minute you’re driving down the road on a rainy day, and the next thing that happens is that, you lose control of your vehicle, it slides or spins and then you careen into the guardrail or off the road.  Or, worse yet, you end up crashing into another vehicle. [27]

Hydroplaning, which happens when a car, motorcycle, or truck’s tires become separated from the road surface by a layer of water, can be caused by excessive speed or poor tire treat, but in many cases, it is caused by something completely out of the driver’s control – road defects.

Common road defects that can lead to hydroplaning include:
•    Improperly designed roadways.
•    Lack of appropriate warning signs.
•    Insufficient cross slope (the slope from the middle of the road to the side of the road which helps prevent pooling of water).
•    Poor road maintenance.

A 1985 study by Rumar, [37] using British and American crash reports as data, found that 57% of crashes, were due solely to driver factors, 27% to combined roadway and driver factors, 6% to combined vehicle and driver factors, 3% solely to roadway factors, 3% to combined roadway, driver, and vehicle factors, 2% solely to vehicle factors and 1% to combined roadway and vehicle factors

All these causes of road crashes are grouped into three namely: [5]

  • Human Factor
  • Mechanical Factor
  • Environmental Factor

In this research, therefore the road geometry, the road furniture, and road pavements are the factors that will be looked into, all of which falls under the environmental factor that cause road accident.



This work investigates the extent highway design and construction practice have affected the safety of lives and properties of road users in Nigeria. The problem is that over the years, lives that were lost on our roads are attributed to many factors without looking at the road itself. Some of the factors, often identified include human factors (ie driver related) and unscientific fatalistic reasons (eg claims that an enemy uses charms / black magic to send the accident to the victim). So the problem is how to discover statistically or otherwise the contribution of road traffic crashes.




This research work is significant in the following ways:

(i). It shall make clear the major contributory factor to road accident.

(ii). The research work shall serve as a contributing literature to this topic. There is very limited literature on this topic at the moment.

(iii). The work shall reveal the existing road conditions in our society

(iv). It will help to raise the consciousness of future road contractors of the need to build roads that will not be killer traps

(v). The work shall help traffic managers to beef up patrol around identified bad or black spots of the road network, so as to save more lives

(vi). This work is expected to contribute and help the Federal Government of Nigeria key into the UN decade for action on road safety



Highway design and construction practice has impacted on the safety of Nigeria roads. The scope of the study is limited to the impact of highway design and construction practice. Most roads in Nigeria have some flaws in the design and construction. Thus, this study shall investigate the good and the bad effects of highway design and construction practice on our roads. The work is divided into five chapters. Chapter one is on introduction. In it, the background of the study was discussed. The objectives of the study, the scope of the study and finally the significance of the study, are also discussed. In chapter two, different literatures on this topic are reviewed. Also in literature review, different road sections and geometry are discussed bearing in mind their various contribution and effects on the safety of our roads. Chapter three discusses the methodology applied in carrying out the research. The methods include identification of various sources of data, design of the questionnaire, collection of data using questionnaire, interviews and visits to various accident sites (i.e. observational methods). Chapter four analyses the collected data and results used to develop models. Finally, chapter five discusses the results, gives necessary recommendations and draws conclusions.

This research is limited to the Road Traffic Crash (RTC) data from the four states that make up zone 9 Enugu according to Federal Road Safety Corps (FRSC) formation in Federal Republic of Nigeria. The states are Enugu, Imo, Abia, and Ebonyi. The case study roads visited are mostly those in Enugu State. The respondents were road safety officers and men, engineers, transport operators and road users that could be reached for study.



(i). To investigate the way in which highway design and construction practice have impacted on the safety of Nigerian road users

(ii). To identify and investigate the contribution of road condition to highway safety

(iii). To open public debate / discussion on the contributing effects of highway sections and geometry to the safety of Nigeria roads

(iv). To identify and investigate the rates of crashes at selected black spots in Nigeria and develop a taxonomy (classification of such “accident – prone” black spots. )

(v) To develop a framework for the computation of road safety Index in Nigeria for design and construction management purposes

(vi) Implant a prototype scoring- based decision support system for road safety Analysis in Nigeria


In conducting this study, the following questions were relevant.

  1. What factors are responsible for accidents on the roads?
  2. Is there any relationship between accident occurrence on roads and nature of the road (Specifically design and construction engineering related factors)?
  • Are majority of accidents on the roads as a result of road conditions?
  1. Do design practice and construction methods affect or contribute to the non-standard nature of Nigeria roads?
  2. Do the non – standard nature of Nigerian roads result in the high frequency of accidents and vulnerability of road users?

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