CHAPTER TWO

ASSESSMENT OF ROAD HAZARDS AND CHALLENGES IN NIGERIA (A CASE STUDY OF MINNA-ABUJA ROAD)

INTRODUCTION

Our focus in this chapter is to critically examine relevant literature that would assist in explaining the research problem and furthermore recognize the efforts of scholars who had previously contributed immensely to similar research. The chapter intends to deepen the understanding of the study and close the perceived gaps.

Precisely, the chapter will be considered in three sub-headings:

• Conceptual Framework
• Theoretical Framework and
• Theoretical Review

2.1CONCEPTUAL FRAMEWORK

Hazard, vulnerability, and risk

The study of adverse transportation events can be broadly divided into transportation hazard analysis, vulnerability analysis, and risk analysis. The focus in hazard analysis is identifying threats to a transportation system, its users, and surrounding people and resources. This is also referred to as hazard identification. The term ‘hazard’ is often used to refer to environmental threats like fog, wind, and floods, but transportation hazards exist at all scales from a sidewalk curb that might trip a pedestrian to the potential for sea- level rise to flood a coastal highway. In the most general sense, a hazard is simply a threat to people and things they value. Vulnerability analysis focuses on variation in the susceptibility to loss from hazardous events. Vulnerability can be viewed as the inverse of resilience, as resiliency implies less susceptib ility to shocks. Risk analysis incorporates the likelihood of an event and its consequences, where an event can range from a minor road accident to a dam break that inundates an urban area. For example, identifying the lifelines in a given area that might be compromised by a landslide would be transportation hazard analysis. The loss of a lifeline to a landslide, or a reduction in its service, will have varying consequences depending on the design of the lifeline, its importance in the system, and the spatial economic consequences to the region. Analyzing this variation would constitute vulnerability analysis. In risk analysis, the likelihood of a landslide and its associated consequences would both be incorporated, often with the goal of identifying potential landslides that represent an ‘unacceptable’ risk. The following sections review these three areas in greater depth.

Hazard analysis

There are many questions that drive transportation hazard analysis. In the simplest case, we could assemble a list of the potential hazards that might affect transportation systems in a region. This could be accomplished by creating a hazard matrix (hazard against travel mode) that indicates whether a given hazard threatens a mode. The next level would be to identify where and when these events might occur. This is typically approached from two perspectives. In one case, we might map the potential for each hazard in a region and overlay areas of high hazard with road, rail, pipeline, and transmission networks to identify points where the two coincide. In the second case, we could select a link and inventory its potential hazards. The first approach requires a method for hazard mapping. This can be further divided into deductive and inductive modeling approaches to hazards mapping (Wadge, et al, 1993). In a deductive approach, an analyst builds a physical process model using governing equations. For example, if landslides are the hazard in question, one could use slope instability equations to determine landslide hazard along a road. In an inductive approach to landslide hazard mapping, an empirical study is undertaken to map past events to determine the conditions that lead to their occurrence. Areas with similar characteristics are then identified, often with techniques in map overlay, because they may also be hazardous. The line between inductive and deductive approaches should not be drawn too sharply because most hazard analyses rely on both. For example, past events may be studied to help build a deductive process model.

There are a number of important dimensions in transportation hazard analysis, most notably the spatial and temporal scales. The spatial scale includes both the extent of the study and the resolution or detail. The spatial extent might be global, national, regional, local, or an individual link in a network. Detail and spatial extent are correlated, but as computer storage continues to increases, this is weakening, and we may soon see national (or larger) studies with very fine spatial and temporal detail. The temporal extent and resolution are also important. A central question is the time-horizon of the study, which can range from a single time period (cross sectional) to any duration (longitudinal). Time is also important because of the many cycles that affect the potential for hazards. Road icing is most common at night in the winter, thus it varies seasonally and diurnally. Landslides occur more often during the rainy season, avalanches occur in the winter and fires during the dry season.

Hazards to transportation systems

There are many environmental hazards that may damage or disrupt transportation systems, and we only review the more common ones here. For exa mple, figure 3 depicts familiar road hazards grouped by their principal effect along with some of their causal relationships. In general, road hazards can: 1) compromise the quality of the surface, 2) block or damage infrastructure, 3) compromise user visibility, 4) compromise steering, 5) create a temporary obstacle, or 6) some combination of the prior five. From the figure, it is clear that rain, wind, and earthquakes have causal links with many other hazards. Rain and earthquakes can both induce a flood, landslide, rock fall or debris flow. Earthquakes can also start a fire or result in a toxic release. Extreme wind can kick up dust, start a fire, drive smoke from a fire, blow trees and debris into the roadway, or redeposit snow leading to an avalanche. This is only a sample of the many hazards and relationships that might exist. Hazards can also coincide, as in a nighttime earthquake in severe rain. This section reviews recent research in the analysis of many of these hazards, but it should not be considered comprehensive. The review is multi- modal and driven primarily by these questions:

1. What is the hazard?
2. What has been done to address the hazard in research and practice?
3. What travel modes does the hazard affect?
4. How well can we predict the hazard in space and time?
5. What are the consequences of the hazard and how are they defined and measured?
6. What mitigation actions exist and what might be developed?

Avalanches

An avalanche is a sudden transfer of potential energy inherent in a snow pack into kinetic energy. The principal contributing factors include snow, topographic effects, and wind which can redeposit snow. ‘Snow structure’ refers to the composition of its vertical profile, which can become instable as new layers are added. An avalanche occurs when the strength of the snowpack no longer exceeds the internal and external stresses. Avalanches are typically divided into ‘dry or wet’ and ‘loose or slab’ avalanches. Dry slab avalanches accelerate rapidly and can reach speeds in excess of 120 miles per hour, but wet avalanches move much slower.

The systematic study of avalanches in North America dates back to the 1950’s in Alta, Utah. This depicts the most active and damaging slide paths in Alta. The most useful, general reference is McClung and Schaerer’s (1993) avalanche handbook. Avalanches typically reduce the serviceability of a road, but they can also damage infrastructure and cause injury or death. Other modes affected include rail, pipelines and transmission lines. The science of predicting the timing of avalanches is called forecasting (Schweizer, et al., 1998), and it has improved significantly over the last fifty years. Snow pits, weather instrumentation, field observation, and remote sensing are combined to forecast avalanches. The corridors that receive the greatest attention are those with high traffic volume and a documented avalanche history. Avalanche path identification using terrain and vegetation is also a common task in areas where historical records may not be available.

Three challenges that transportation agencies face in avalanche control include: 1) selecting paths where mitigation would be most beneficial, 2) evaluating mitigation measures, and 3) comparing the risks of different roads. The avalanche- hazard index (Schaerer, 1989) combines forecasting with traffic flow volumes to address these needs. The index includes the likelihood of vehicles being impacted by an avalanche along a road as well as the potential consequences. It also incorporates the observation that loss of life can occur when a neighboring ava lanche overcomes traffic halted by another slide.

A number of avalanche risk case studies for transportation corridors have been performed that include Glacier National Park (Schweizer, et al., 1998), the Colorado Front Range (Rayback, 1998), and the Himalaya (De Scally and Gardner, 1994). Avalanche mitigation options, increasing in cost, include explosives, snow sheds, and deflection dams. Rice, et al. (2000) provide an example of system for automatically detecting avalanches on rural roads.

Earthquakes

The study of earthquakes and seismic risk spans many fields in the sciences and social sciences. They are widely researched by transportation engineers from a variety of perspectives because they can severely damage and disrupt transportation systems. A devastating earthquake epitomizes a low-probability high-consequence event in risk analysis. The recurrence interval for a large earthquake in a region can be centuries, varying inversely with magnitude, yet devastating earthquakes occur almost every year somewhere in the world. For many populated areas without a history of severe earthquake loss, the likelihood of facing an earthquake that damages transportation lifelines is a near certainty because the geologic record reveals past large earthquakes (Clague, 2002). No major transport mode is exempt from the adverse affects of an earthquake. Roadways, railways, pipelines, transmission lines, and air and sea ports can all be damaged with tremendous economic costs (Cho, et al., 2001). Earthquakes can also start fires, trigger landslides (Refice and Capolongo, 2002), release toxic chemicals (Lindell and Perry, 1996), cause dam failures, and create sudden earthen dams via landslides leading to inevitable flooding (Schuster, 1986).

Pre-impact earthquake research in transportation engineering focuses on vulnerable structures like bridges (Malik, 2000), tunnels (Hashash, et al., 2001), and water delivery systems (Chang, et al., 2002). The central problem is estimating the response characteristics of these structures to ground shaking and liquefaction (Price, et al., 2000; Selcuk and Yuceman, 2000; Sevtap and Semih, 2000; Romero, et al., 2000). Werner (1997) notes that earthquake losses to highway systems depend not only on the response characteristics of the highway components, but also on the nature of the overall highway system’s configuration, redundancy, capacity and traffic demand (see also Basoz and Kiremidjian, 1996). For example, two bridges may be equally susceptible to ground shaking, but one may be much more important in serving the daily travel dema nd to an important destination. Retrofitting is typically in high order when a bridge highly susceptible to the effects of an earthquake is also essential in serving a large volume of travel demand.

Post-impact earthquake research focuses on immediate damage assessment (Park, et al., 2001), the performance of the transportation system (Chang, 2000), and the lifeline restoration process (Isumi, et al., 1985; Opricovic and Tzeng, 2002). Chang (2000) examines post-earthquake port performance following the Kobe quake in 1995 and frames the economic loss (and thus vulnerability) in terms of three types of traffic: 1) cargo originating from or destined to the immediate hinterland, 2) cargo from/to the rest of Japan, and 3) foreign transshipment cargo. By examining the pre and post conditions of these cargo types, Chang concludes that (2) and (3) suffered the most resulting in both short-term loss of revenue and long-term loss of competitive position. Economic impacts may last beyond the point where the infrastructure has been repaired. Kobe demonstrates that (3) is especially important, and the central port vulnerability question can be framed as the percent that a port's revenue is tied to transshipment cargo.

Floods and dam breaks

Floods cause the greatest loss in many countries because they occur frequently and their severity is compounded by dense development along many rivers. The National Weather Service (NWS) in the U.S. estimates that greater than half of all flood-related deaths occur in vehicles at low-water crossings. Flood damage to transportation systems represents one of the largest losses in the public sector. Intense rainfall is the chief cause of floods, but hurricanes also hold the potential to cause a significant amount of storm surge inundation. Dam breaks are included here as a special type of technologically- induced flood. This includes earthen dam breaks caused by earthquake- induced landslides (Schuster, 1986). The modeling of dam breaks has increased in recent years because agencies such as the U.S. Bureau of Reclamation (USBR) are required to submit a report and associated inundation animations of potential dam breaks to local emergency managers downstream from all dams for emergency planning purposes.

Flooding is a serious problem in many areas because of its ability to rapidly degage the serviceability of a transportation network at various points. Ferrante, et. al. (2000) combine a numerical model for flood propagation in urban areas with a network path- finding algorithm to identify “least- flood-risk” paths for rescuing people as well as providing relief. They use Dijkstra’s (1959) shortest path algorithm, but the cost of a link is calculated in a very novel manner using the flood flow depth and velocity across the road. In this way, the “cost” of traversing a link is a function of both the length of the road as well as its flood characteristics.

Fog, dust, smoke, sunlight and darkness

Fog, dust, smoke, sunlight and darkness are transportation hazards that compromise the visibility of system users. This hazard category does not apply to pipeline networks, transmission lines, and other networks where visibility is not an issue. From a roadway perspective, Perry and Symons (1991) provide an excellent source on these hazards. Musk (1991) thoroughly covers the fog hazard, and Brazel (1991) describes a dust storm case-study for Arizona. Although smoke from wildfires routinely disrupts roadways and inhibits operations at airports each summer, it appears to be an under-researched topic in transportation hazards. Darkness also has an understandably adverse effect on road safety, especially whe n combined with fog, smoke or dust.

Fog can cause spectacular road accidents involving hundreds of vehicles on a roadway. Musk (1991) describes the Fog Potential Index (FPI) which expresses the susceptibility of a location p on a road to thick radiation fog on a scale from 0 to 100. The values of two locations are comparative in that a value of 30 at location A and a value 20 at location B means that location A should experience 50% more hours of thick radiation fog than location B.

Rain, snow and ice

Rain, snow and ice are common hazards that compromise visibility and the quality of a road, rail or airport surface (Benedetto, 2002; Andrey, 1990). All road users are familiar with road signs like “slippery when wet” or “bridges may be icy” (Carson and Mannering, 2001). Ice is also a hazard for aircraft because of its effect on lift, as well sea travel because it creates obstacles (Tangborn and Post, 1998). In a road network context, skidding is the most common explanation for accidents that occur in the context of these hazards. The skidding rate is the statistic used to quantify this factor, which is the percentage of accidents where one or more vehicles are reported to have skidded (Perry and Symons, 1991). Example skidding rates for cars are given in figure 6 for Great Britain in 1987. This figure shows that rain roughly doubles the percentage of accidents where skidding is a factor over dry conditions, and snow and ice quadruple the rate over dry conditions. The overall skidding rate for cars for all road conditions is about 14%.

The question of how rain, snow, and ice affect the total number of road accidents is not straightforward. Palutikof (1983) found that people drive more carefully in snow or simply postpone or cancel journeys. This leads to reduction in the total number of accidents over that which would be expected. Rain does not seem to have the same effect on travel decision making, and Brodsky and Hakkert (1988) found that the number of accidents increases in wet conditions. Al Hassan and Barker (1999) found a slightly greater drop in traffic activity owed to inclement weather on the weekend (> 4%) than on weekdays (< 3%). In a case study of Chicago, Bertness (1980) found that rain roughly doubled the number of road accidents with the greatest effect in rural areas. It is important to keep in mind that rain, snow, and ice studies tend to underestimate the risk because road accidents are typically underreported.

Hazards that affect the road surface represent the most costly maintenance function for many cities, counties, and state transportation departments. Salt is the most common road de-icer with about 10,000,000 tons applied each year in the U.S. (Perry and Symons, 1991). This is expensive and comes with environmental side effects. Eriksson and Norman (2001) note that road weather information systems have a very high benefit- cost ratio in reducing weather-related risk. The widespread adoption of Doppler radar has greatly improved the reporting of precipitation, and some systems can now report rain- intensity to levels as detailed as an individual street segment. There is much work in developing and installing in situ road sensors to automatically detect poor road conditions. This can greatly improve road maintenance procedures because managers can apply mitigation measures like salt where it is most needed.

Landslides, rock fall, and debris flow

Many miles of roads, rail, and pipeline travel through areas with rock faces and steep slopes in mountainous terrain. Geomorphic hazards that commonly affect transportation corridors include landslides, rock fall, and debris flow. A debris- flow is essentially a fast- moving landslide. These hazards can damage or reduce the serviceability of infrastructure, crush or bury vehicles, and result in death. In some cases they occur without little or no warning, but they are typically preceded by intense rain (Al Homoud, et al., 1999). They can also be earthquake or volcanically induced (Dalziell and Nicholson, 2001) and create sudden earthen dams that lead to flooding (Schuster, et al., 1998). An excellent, general source on landslides and debris flows is the Transportation Research Board (TRB) report on Landslides edited by Turner and Schuster (1996). In terms of case studies, Marchi et al. (2002) examine ten years of debris flows in the Italian Alps, Evans and Savigny (1994) examine landslides in Canada, He, et al. (2002) looked at debris flows along the China-Nepal Highway, Budetta (2002) conducted a risk assessment for a 1 km stretch of road subject to debris flows in Italy, and Petley (1998) examined geomorphic road hazards along a stretch of road in Taiwan. Fish and Lane (2002) discuss a rock-cut management system, and Franklin and Senior (1997) describe a rock fall hazard rating system.

Bunce, et al. (1996) provide an excellent example method for assessing the risk of loss of life from rock fall along a highway. They used rock fall impact-mark mapping supplemented by documented rock fall records to establish a rock fall frequency for the Argillite Cut on Highway 99 in British Columbia. The method relies on separate calculations for the risk of a rock hitting a stationary vehicle versus a moving vehicle, as well as a moving vehicle hitting a rock on the road.

Wind, tornados and hurricanes

Wind is a significant hazard to road, rail, sea, and air transport (Perry and Symons, 1994). Gusts, eddies, lulls, and changes in wind direction are often greatest near the ground in extreme wind episodes. In these episodes, the majority of fatalities are generally transport related. It is difficult to summarize the effects of wind on road and rail transport because little data exists, although it is generally viewed as less of a hazard than ice, snow, and rain. Figure 7 depicts wind that is blowing smoke across an interstate and blocking traffic. Perry and Symons (1994) divide the wind hazard into three categories: direct interference with a vehicle, obstructions, and indirect effects. Direct interference includes its effects on vehicle steering, which may push one vehicle into another or run a vehicle off the road. Extreme winds can overturn high-profile trucks and trains when the wind vector is orthogonal to the direction of travel because the force of the wind is proportional to the vehicle area presented (Baker, 1988). Wind can impede transport by blowing dust or smoke across a road, which can reduce visibility. It can also blow trees and other debris onto a road or railway and create temporary obstacles. Indirect effects include the redeposition of snow leading to an avalanche, as well as its adverse effect on bridges and air and sea-based termini. Overall, wind can impede transport operation or damage vehicles and infrastructure, all of which can result in economic impacts, injuries, and fatalities.

Air transport faces the greatest hazard from wind. A violent downdraft from a thunderstorm (microburst) on takeoff or landing is one example, but any exceptionally large local wind gradient (wind shear) can affect lift adversely at low altitudes (Vorobtsov, 2002; Goh and Wiegmann, 2002). In many air disasters, wind is considered the primary contributing factor. Small aircraft are much more vulnerable to in- flight storms and are often warned to completely avoid storms. Measures to reduce wind hazard include permanent wind breaks, warnings, road closures, and low- level wind shear alert systems. An airport wind-warning system generally consists of a set of anemometers that are analyzed by computer. A warning is issued when levels differ by some threshold. Automated wind-warning systems for individual roads may appear soon because of advances in weather instrumentation. The finest level that wind warnings are commonly issued is at a county scale. Improved weather forecasting is generally viewed as the principal means for reducing the hazard (Perry and Symons, 1994).

Hurricanes and tornados represent special cases of extreme winds. Due to satellite, radar, and other in situ sensor networks, their prediction has greatly increased in recent years. Much of the transportation research in this area focuses on evacuation. Wolshon (2001) reviews the problems and prospects for contraflow freeway operations to reduce the vulnerability of coastal communities by reversing lanes to increase freeway capacities in directions favorable for evacuation. This problem is simple conceptually but represents a significant challenge for both traffic engineers and emergency managers.

Wildlife

Wildlife is a familiar hazard to most drivers because of the many warning signs along roadways. Wildlife accidents typically result in vehicle damage, but they can also result in injury or death. Two common examples of wildlife hazards include the threat that undulates such as moose (Joyce and Mahoney, 2001) present to vehicles and the threat that birds present to aircraft. The number of these collisions is staggering, and it is estimated that in 1991 greater than half a million deer were killed by vehicles in the United States (Romin and Bissonnette, 1996). Lehnert and Bissonette (1997) review research on deer-vehicle collisions and describe a field experiment on the effectiveness of highway crosswalk-structures as a means of mitigation. The crosswalk system evaluated forces deer to cross at specific areas that are well marked for motorists. Although deer fatalities decreased by 42% following the installation of the crosswalks, they were unable to attribute this reduction to the crosswalks because there was an 11% probability that it may have occurred by chance.

Bird hazards to aircraft are also a significant concern, and Lovell and Dolbeer (1999) provide a recent review with a study to validate the results of the U.S. Air Force (USAF) bird avoidance model (BAM). BAM provides information to pilots regarding elevated bird activity based on refuge surveys, migration dates, and routes. Lovell and Dolbeer note that since 1986, birds have caused 33 fatalities and almost $500 million in damage to USAF aircraft alone. On average, USAF aircraft incur 2,500 bird strikes a year with most occurring in the fall and spring migration. Waterfowl and raptors account for 69% of the damaging strikes to low- level flying military aircraft. Lovell and Dolbeer found that BAM predicted significantly higher hazard for routes where bird strikes have occurred in the past and thus can assist in minimizing strikes.

Transportation as hazard

In addition to the many environmental hazards that threaten transportation systems, transportation itself presents hazards to people, property, and the environment. Road traffic accidents are the most common example, and the majority of transportation casualties in most countries can be attributed to road accidents. The contributing factors for road accidents are typically classified into those associated with the driver, vehicle, and the environment. Contributing factors associated with the driver include error, speeding, experience, and blood-alcohol level. Factors associated with the vehicle include its type, condition, and center of gravity. Environmental factors include the quality of the infrastructure, weather, and obstacles. The majority of road accidents are attributed to driver factors (Evans, 1991), and this holds for many other modes such as boats (Bob-Manuel, 2002), bicycles (Cherington, 2000), snow mobiles (Osterom and Eriksson, 2002) and all terrain vehicles (Rogers, 1993). Taken together, this implies that most transportation casualties in the world are road accidents chiefly attributed to the driver. Not surprisingly, research on driver factors represents the largest area of transportation hazards research (see the journal Accident Analysis & Prevention). Transportation accidents have severe effects on those directly involved, as well as side effects to others. Other effects might include severe traffic delays leading to missed meetings, lost sales to businesses, delayed commodity shipments, and increased insurance costs. Research in accident analysis spans all modes and typically focuses on assessing the role of various driver, vehicle, and environmental factors as well as methods for mitigating accidents. (See chapter on incident management).

In addition to common traffic incidents, there are also low-probability high-consequence transportation events that place risks on people and environmental resources in proximity to transportation corridors and ports. Rail, road, pipeline, and marine HazMat transport is the prime example in this area because it places considerable involuntary risks on people (and resources) who do not perceive much benefit to the transport of hazardous materials. HazMat has been studied from a number of perspectives for many materials and modes, so there are numerous frameworks for analysis (Bonvicini, et al., 1998; Cassini, 1998; Erkut and Ingolfsson, 2000; Fabiano, et al., 2002; Helander and Melachrinoudis, 1997; Jacobs and Warmerdam, 1994; Klein, 1991). Aldrich (2002) provides an historic perspective on rail HazMat shipments from 1833 to 1930, and Cutter (1997) reviews recent trends in hazardous material spills. Caputo and Pelagagge (2002) present a system for monitoring pipeline HazMat shipments. Singh, et al. (2002) examine the spontaneous coal combustion in sea transport. Raj and Pritchard (2000) present a risk analysis tool used by the Federal Railway Administration. Hwang, et al. (2001) present a comprehensive risk analysis approach for all modes that includes 90% of the dangerous chemicals. Abkowitz, et al. (1990) describe a method for evaluating the economic consequences of HazMat trucking. Verter and Kara (2001) review HazMat truck routing in Canada. Dobbins and Abkowitz (2002) look at inland marine HazMat shipments. Saccommano and Haastrup (2002) focus on HazMat risks in tunnels. Marianov, et al. (2002) propose that proximal communities receive a tax reduction to offset the risk of proximal HazMat shipments.

Following the events of September 11th 2001, transportation security has become a national research priority led by the Transportation Security Administration (TSA) recently reorganized under the Department of Homeland Security. Transportation terrorism has not been a focus of transportation hazards researchers in the past, so there is little to review at this point. However, reports and proposals are beginning to surface that indicate that this will be one of the largest areas of transportation hazards research for many years.

Transportation in emergency management

Transportation lifelines are vital during an emergency, and play an important role in all four phases of emergency management: mitigatio n, preparedness, response, and recovery. The concern in the mitigation phase is reducing the likelihood of an event, its consequences, or both. The focus of the preparedness phase is improving operational capabilities to respond to an emergency such as training emergency personnel, installing notification systems, and redeploying resources to maximize readiness (Sorensen, 2001). The mitigation and preparedness phases both help reduce the impact of hazardous events. The response phase begins immediately following an event, and this is when plans devised in the preparedness phase as well on-the-fly plans are activated. Common concerns include evacuating and sheltering victims, providing medical care, containing the hazard, and protecting property and the environment. The recovery phase addresses longer-term projects like damage assessment and rebuilding, which feeds back into the mitigation phase because this phase presents an opportunity to rethink hazardous areas.

Mitigation strategies for specific hazards and assets were discussed in the prior section on hazards to transportation systems. The overarching challenge in the mitigation phase is identifying and prioritizing mitigation projects in a region and allocating scarce resources to their completion. Benefit-cost analysis is a valuable method in this regard, but it must be preceded by risk assessments for all potential hazards. The effectiveness of the mitigation strategy is also important, and this can be considered part of the benefit.

Research in the preparedness and response phase has been fueled by new technologies. Enhanced 911 (E-911) is a significant relatively recent innovation, and this is covered in the chapter on incident management. Relevant topics that are actively researched in this phase include optimally locating emergency teams (List and Turnquist, 1998), locating and stocking road maintenance stations, optimal fire station location for urban areas and airports (Revelle, 1991; Tzeng and Chen, 1999), and installing hazard-specific warning systems. Evacuation planning in this phase focuses on delimiting emergency planning zones (Sorensen, et al., 1992), designing and simulating evacuations (Sinuany-Stern and Stern, 1993; Southworth, 1991; Cova and Johnson, 2002), developing and testing evacuation routing schemes (Dunn, 1993; Yamada, 1996; Cova and Johnson, 2003), and identifying potential evacuation bottlenecks (Cova and Church, 1997). Reverse 911 systems that allow police to call evacuees are becoming increasingly important in dealing with notification. State-of-the-art systems allow emergency managers to send custom messages with departure timing and routing instructions to zone s defined on-the- fly with a mouse. Other research in the preparedness and response phase include methods for keeping roadways open following an earthquake or landslide (Santi, et al, 2002).

One problem that complicates emergency planning by transportation agencies is the increasing amount of development in many hazardous areas. This is nearly universal as populations increase in floodplains, coastal areas subject to hurricanes, fire-prone wildlands, areas near toxic facilities (Johnson and Zeigler, 1986), regions at-risk to seismic activity, and so on. This presents a problem because in many of these areas (and at many scales) the transportation system is not being improved to deal with these increasing populations. This means that evacuating threatened populations is becoming increasingly difficulty at all scales, as new development occurs. In other words, vulnerability to environmental hazards is continually increasing owed both to the fact that populations in hazardous areas are increasing at the same time that the ability of emergency managers to invoke protective actions such as evacuation are decreasing.

Uncommon road safety hazards

Soiled road surface

Motorists can encounter areas soiled with various substances, such as mud/ dirt carry-out, fallen goods or sand, fuel or oil spillage and sudden change of the surface type and condition (patch of ice, puddle, etc.). When faced with an uncommon safety hazard the drivers' reaction is in most case natural, i.e. he or she initiates hard braking or an evasive manoeuvre with the purpose to avoid the obstacle. Without anti-skid braking system (ABS) or one of the stability enhancement systems (such as ESP) vehicles often become unstable and break away.

Making right decisions when faced with unexpected and extraordinary safety hazard requires knowledge and skills which in most cases exceed the average driver's capabilities. Reference can be made to the road accident in which a car ran over a layer of spilled grain. It was determined that the driver of the vehicle moving on the surface covered with grain lost control of the car as a result of the undertaken evasive manoeuvres. The vehicle crossed into the opposing traffic lane where it crashed into an oncoming car.

The analysis of the causes of the above-described accident involved, among other things, investigating what sensory and motor functions were at the drivers disposal at that time. He needed to identify the encountered unusual (non-typical) hazard situation to decide whether to brake hard or gently or do nothing i.e. continue driving without any extra manoeuvres.

For this purpose an experiment was performed on runways of a disused military airfield. Two strips of grain, each ca. 0.5m wide spaced by a distance corresponding to the wheel track were placed on the test section. The grain layers were ca 0.02 m thick. The test section was 70 m long. The experiment was carried out jointly by the research teams of the Forensic Investigation Institute in Kraków and of the Poznań University of Technology. The research method and the actual experiment are reported elsewhere. The total number of seventeen braking tests were carried out on a wet asphalt pavement contaminated with grain for different initial speed values in the range of 80- 120 km/h.

The outcomes demonstrate that contamination of the road surface with grain has a significant adverse effect on the braking performance. This could be well expected, yet still the motorists are often not fully aware of the consequences of running into spilled grain. On the test surface a drastic drop of the braking distance was noted – by ca. 60% as compared to a wet reference surface without grain.

In a test using a car equipped with ABS system hard braking on the section contaminated with grain did not result in any sign of a loss of stability or problems with keeping the car straight. Over the course of the experiment a few test runs were also made at speeds of up to 120 km/h without braking. The purpose of these tests was to check if spilled grain can cause any adverse effects leading to loss of stability. Directional control was maintained during all the test runs.

This demonstrates that without braking or evasive manoeuvres undertaken by the driver the accident would not have happened. Hence an obvious conclusion that the driver must have ignored the hazard related to the contaminated road surface and went on driving as if nothing happened. The rear wheel drive of the vehicle (without traction control system) caused skidding and loss of directional stability. This led to a head-on crash with an oncoming vehicle. The results of the investigation turned out to be different and contrary from the previous knowledge on good driving practice in such non-typical conditions A vehicle running at a constant speed over a section covered with spilled grain did not lose directional stability owing to the sufficient grip of the wheels. Were it not for the driver's emergency reaction, the vehicle would have continued without breaking away since the grip on the surface contaminated with grain is similar to the grip on compacted snow. Moreover, the tests confirmed that vehicles equipped with ABS are able to maintain directional stability during hard braking on such surfaces.

Split-mu braking

It happens that a vehicle travels off the side of the road onto the shoulder or runs in a surface with varying friction coefficient and starts hard braking as a result. If a vehicle is fitted with ABS and the driver has sufficient skills to effectively perform emergency braking than in most cases the situation can be brought under control. Without such as system or in the event of its failure the vehicle will behave in a different manner. Without ABS assistance the vehicle suddenly loses its directional stability and changes its path in an uncontrolled manner. Unless specifically trained, most drivers are not aware of such braking behaviour on split-mu surfaces. Without such knowledge and skills required in such situations the drivers react naturally making emergency manoeuvres which, when inappropriate to the situation, can have serious consequences and pose a safety hazard for other road users.

Special field tests were developed to check the behaviour of vehicles with and without ABS during hard braking on split-mu surfaces. In the test two side wheels travelled on the surface contaminated with grain with the other two on a clean surface.

Explosive decompression of tire

Explosive decompression is typical of heavy truck tires. This kind of tire failure can be attributed to errors during operation, resulting in weakening of the structural components of the tire and an increase of the tire temperature. Similar damage can result in tyre blow-out due to decompression. Another potential cause of tire blow-out is sidewall damage which can lead to sudden release of air and loss of stability of the vehicle.

Explosive decompression is always preceded by the primary damage located in the sidewall, in the shoulder or in the tread. The effect of the tire failure on the vehicle stability depends on the place of the initial damage. The most common failure modes are:

1. explosive decompression through the tire tread tearing apart the rubber, the steel carcass cords and the bead. The sudden release of air generates a vertical force acting on the vehicle in the direction from the surface up. The resulting rapid loss of air pressure in the tire reduces the tire radius and results in side pulling of the vehicle. Braking will intensify the side pull.
2. explosive decompression through the tire shoulder makes the vehicle change the direction under the effect of a new side force and the force of inertia.
3. explosive decompression through the tire shoulder (Fig. 4) poses the biggest safety hazard. The whole process is too short for the driver to react to pulling and during rapid deflating the vehicle is pulled aside losing stability and steerability. The forces acting on the tire push it away from the rim and can even strip it completely from the wheel. The side forces generated by the blowout cause the vehicle to swerve and potentially even overturn.

Causes of Road Accidents Provoking injuries and Deaths in Nigeria

The causes of road accidents in Nigeria are basically divided into three:Human factors, Mechanical factors and Environmental factors (Ukoji, 2014). The human factors include; Visual (Eyes) problem, driver fatigue, poor knowledge of road signs and regulations, illiteracy, health challenges, excessive speed, drunkenness, drug abuse, lack of concentration and over-confidence while driving among others. In addition, poor budgetary allocations and contract evaluation could be seen as one of the human factors. Poor funding for road construction, embezzlement as well as misappropriation of Federal Road Safety Commission (FRSC) funds leads to insufficient human and material resources to man and manage the roads. This according to Sumaila (2013), encouraged armed robbers to carry out their ungodly activities around the bad portions of the roads and the bad roads also predispose road crashes. The indiscriminate use of sirens coupled with very high speed rates by political public office holders such as government vehicles’ drivers’ has been reported to cause a lot of road traffic accidents in Nigeria (Agbeboh & Osabuohien-Irabor, 2013). For instance in 2016, a renowned Nigerian Professor Iyayi was a victim of such incident, he died in an accident involving the convoy of Kogi State Governor, Captain Idris Wada of Kogi State.

The mechanical factor ranges from engine problems, brake failure, poor vehicle maintenance, and use of expired tyres that get busted on the road. Nigeria like other African countries imports second hand vehicles from Asia, Europe and the United States. There are import standards and age limits for vehicles coming into the country, but enforcement of the standards is not strict as government agencies saddled with the responsibility of enforcing compliance usually compromise in the face of monetary inducement. Moreover, vehicle safety laws do not effectively enforce safety standards, and enforcement of vehicle inspection regulation is weak.

The environmental factors may be natural such as heavy rainfall leading to slippery roads, harmattan, reflection of sun rays on windshield, heavy wind, bad and poorly maintained roads e.t.c. These factors no doubt contributed to lack of safety on the roads with the attendant impact on National development. In addition, Ogunsanya (1993) observed that rural urban migration also contributed to road accidents as roads leading to and within large cities like Kano, Kaduna, Lagos, Ibadan, and Port Harcourt faces congestion which in turn leads to accidents due to general impatience and ill-tempered nature of road users.

Impact of Road Hazard on National Development

The implications of road accidents in Nigeria are colossal. Pratte (1998) observed that persons injured in road accidents on Nigerian highways no longer participate in the economic mainstream, and this amounts to a loss of labour of millions of person’s years to the nation. The attendant loss of productive human lives, man hour and resources worth billions of naira in a country like Nigeria where fatal road accidents happens on daily basis is better imagined than experienced. The social and psychological traumas associated with road accidents are enormous as a significant number of breadwinners are taken away from their families unexpectedly. The carnage of fire explosion involving petrol tankers, trucks and trailers has lead to the loss of goods and properties worth billion of naira over the years and all these have negatively impacted on the nation development.

Government’s intervention on road hazards and challenges

The attention given to road safety has increased with the adoption of the 2030 Agenda for Sustainable Development. This agenda includes setting a goal of reducing road traffic deaths and injuries by 50% in 2020 among others thereby ensuring the safety of lives and properties on the road. Road crashes and accidents are not properly documented in Nigeria and most times records of accidents say nothing about the cause of such accident. Beside this, simply counting accidents and casualties gives an incomplete indication of the level of road safety (Al Haji, 2003). Therefore, there is a need for road safety performance indicators that are causally related to accidents or casualties, used in addition to a count of accidents or casualties in order to indicate safety performance or understand the process that leads to accidents. The safety performance indicators would reflect the current safety conditions of road traffic system, measure the influence of safety interventions, and compare different road traffic systems (Vis, 2005).

Contrary to the general belief that Nigerians posses very low level of awareness on the causes of road traffic accidents, previous research has shown that Nigerians know quite a lot about what could cause road traffic accidents ( Asalor, 2010). The causes of road traffic accidents depend on a list of factors which can be broadly divided into:

(i) Vehicle operator or driver factors

(ii) Vehicle factors

(iii) Road pavement condition factors

(iv) Environmental factors.

Road traffic accident can be caused by one or a combination of these factors. The Federal Road Safety Commission (FRSC) is the government agency with statutory responsibilities for enforcement of road safety regulations in Nigeria. The agency was established in 1988 by Gen. Ibrahim Babangida through Decree No.45 of 1988 as amended by Decree 35 of 1992 popularly known as FRSC ACT cap 141 laws of the federation of Nigeria. The commission in recent years appeared to be redundant but for issuance of drivers’ license, vehicles plate numbers and a few regulatory activities. The statutory functions of the Federal Road safety commission according to Agbeboh and Osarumwense (2013) include:

(i) Making the high way safer for motorist and other road users.

(ii) Recommending work and devices designed to eliminate or minimize accidents on the high way and advising the government on what to do about road problem in Nigeria.

(iii) Educating motorist and members of the public on the importance of discipline on the road.

(iv) Design and production of drivers’ license and plate numbers to be used by various road users.

(v) Giving prompt attention and care to victim of road accident, conduct researches into the causes of the accident and method of preventing them and putting into use such findings.

(vi) Determining speed limit for all road users.

(vii) Providing roadside and mobile clinics for the treatment of accident victims free of charge.

These statutory functions of the Federal Road safety commission are laudable. One would expect a safer road where accidents and road crashes is reduced to the barest minimum with the statutory functions highlighted above; but data on road crashes and violent death proves otherwise.

2.2 THEORETICAL FRAMEWORK

Cognitive model

The theoretical framework adopted for this study is the cognitive model. It is a psychological approach that analyses road safety on the basis of cognition. On this note, Michon (1985) provides a review of drivers’ behavior models and a critique of behavioral adaptation theories. His focus is on developing a control theory approach based on understanding the underlying cognitive mechanisms of individuals. This is to allow for the development of a computational framework to predict the implications of different safety policies. Michon’s view is that risk homeostasis and compensatory models do not explain which stimuli affect perceptions of risk, and that they have no individual based theory. He cited the work of Klebelsberg (1971, 1977, published in German) as developing a control process based on balancing subjective and objective risk. He made the argument that when objective risk exceeds perceptions of risk, then there may be a safety problem.

Alternately, when perceptions exceed the objective risk level there is then a safety margin that is too large. Klebelsberg is essentially proposing a risk threshold model similar to Näätänen and Summala (1974); that is safety problems do not arise until a given perception of risk exceeds the objective level of risk. Using a driving simulator, studies have been used to empirically investigate these issues, and have found some empirical support (Lewis-Evans, de Waard, & Brookhuis, 2011).Michon (1989) provides additional discussion of the distinction between “aggregate models” of road user behavior and “process models” of individual driver behavior. This provides a useful dichotomy between economically-based models that describe aggregate behavior and psychology-based models of individual driver behavior. It is stated that the former assume rational behavior, while the latter can explain mental processes and actual behavior. This really gets at the crux of the difference between psychological versus economic approaches to studying road traffic safety. One benefit of economic or aggregate approaches is that they are more practical and easier to develop; alternatively, psychological approaches have been tested using simulator studies which will suffer from caveats as to how realistic they are for modeling real behavior.

2.3 EMPIRICAL REVIEW

In a study by Dudziak et al (2016) on “Uncommon road safety hazards”, the study described certain uncommon road safety hazards resulting from road surface contamination, driving on split-mu surfaces or explosive decompression of car tire. One of the analyzed cases involves a road accident due to inadequate emergency reaction of a motorist after running in road surface covered with spilled grain. A methodology of experimental research allowing to analyse and explain road traffic incidents has been developed. The research results indicate an importance of improving the driving skills, as well as the motorists’ capability to make right decisions on the road.

In another study by Cova (2004) on “Transportation hazards”, the study examined the issue of hazards in transportation. The findings showed that transportation hazards in Nigeria generally are many, diverse in nature, and are caused by man’s interaction with nature (environment) for exploits in a number of ways-both in the cities; where industrial activities predominate, and rural areas; where agriculture thrives. The paper posited that man utilizes air for survival, harnesses land and water resources for domestic, commercial, industrial, agricultural and other purposes. Through these activities; man directly and/or indirectly create problems which are detrimental to transportation. The paper recommended awareness creation and change in attitudes for effective transportation and resources management strategies as a way forward.