IMPACT OF TRAFFIC CONGESTION ON WORKERS HEALTH

A CASE STUDY OF LAGOS STATE, NIGERIA

CHAPTER TWO

LITERATURE REVIEW AND CONCEPTUAL FRAMEWORK

2.1 Literature Review

Traffic Congestion

Traffic Congestion, one of the acclaimed indicators of a city socio-economic vibrancy, has continually challenged the efforts of city and transport planners alike on our highways, in terms of longer travel time and delays over time and space. It has equally created and artificial barrier to a cost effective flow of goods and persons along our highways.

European Conference of Ministers of Transport ECMT, (2007) definition of traffic congestion “Congestion is the impedance vehicles impose on each other, due to the speed-flow relationship, in conditions where the use of a transport system approaches capacity. Congestion is essentially a relative phenomenon that is linked to the difference between the roadway system performance that users expect and how the system actually performs. Congestion is a situation in which demand for road space exceeds supply. (Popoola, 2013)Congestion takes on many faces, occurs in many different contexts and is caused by many different processes. Because of this, there is no single best approach to managing congestion – and the report is therefore not prescriptive about specific congestion management measures. However, there are many things congestion management policies should take into account if they are to achieve the goals they set themselves. Based on Abiola, (2013) research on causes of traffic congestion on highway in Nigeria, he highlighted the problems of intra-urban traffic in Lagos. The study found that 57% of commuters and motorists spend between 30 to 60 minutes on the road due to traffic congestion. He also found that the worst traffic congestion occurred on Mondays.

He further stated the causes of traffic congestion in Lagos to include the following:

Presence of pot holes/bad road, trading activities, illegal parking, loading and discharging of passengers, illegal bus stops, flooding/poor drainage, vehicle breakdown, narrow road sections, religious activities, high volume of traffic, lack of parking space and lack of traffic light at some road intersections, lack of proper traffic impact study of development.

According to Knoflacher (2006), cities in the third world countries face traffic congestion which is mainly caused by the following factors:

The urban set-up is not compatible with the traffic demands, the rate of car usage is high rather than using a car at some point, and then one has to walk or use public transport, little budget is put on car maintenance by owners resulting in slow moving vehicles due to inefficiency, inadequate traffic management measures, flouting of traffic rules by motorists, inadequate public transport, negative Effect of Traffic Congestion.

According to Wikipedia,

Wasting time of motorists and passengers (“opportunity cost”). As a non-productive activity for most people, congestion reduces regional economic health, delays, which may result in late arrival for employment, meetings, and education, resulting in lost business, disciplinary action or other personal losses, inability to forecast travel time accurately, leading to drivers allocating more time to travel “just in case”, and less time on productive activities, wasted fuel increasing air pollution and carbon dioxide emission owing to increased idling, acceleration and braking, wear and tear on vehicles as a result of idling in traffic and frequent acceleration and braking, leading to more frequent repairs and replacement, stressed and frustrated motorists, encouraging road rage and reduced health of motorists, spillover effect from congested main arteries to secondary roads and side streets as alternative routes are attempted (‘rat running’), which may affect neighborhood amenity and real estate prices, higher chance of collision due to tight spacing and constant stopping-and-going.

(Wikipedia)

The main Challenges are traffic congestion, pollution and road accident. Newman and Jeffrey (1999), highlights the negative effects of urban traffic as it contributes to accidents, noise and air pollution as well as traffic congestion on the roads. Traffic also contributes to global warming through the gases which are emitted. Expertise argues that poor planning of transportation system in Nigeria has led to over dependence in motor vehicles resulting in too many vehicles with its accompanied problems including traffic congestion.

Olaogbebikan (2013)examined the traffic management problem resulting from traffic congestion in the on Alaba International Market Road, Ojo, Lagos State Nigeria. It also evaluates the opinion of the stakeholders in the transport sector such as the commuters, transport operators and private car owners on the traffic situations and management problems in the study area.

Popoola, Abiola, Adeniji (2013) says traffic congestion has continually challenging the effort of city and transport planners alike on our highways, in terms of longer travel time and delays over time and space. It has equally created an artificial barrier to a cost effective flow of goods and persons along our high ways linking major towns together. They examined the road user perception to causes effects and remedies to traffic congestion on highway in Nigeria, with mowe/ibafo along Lagos-ibadan expressway our case study area.

The highway traffic conditions across highways in Nigeria are in a grim situation caused by daily congestion and daily accidents. They believed that highway systems are used for daily commuting, transportation of goods and interstate travels. They provide solutions to problems or at least ways to alleviate the magnitude of their occurences.

According to (Mudzengeree, 2013), some of the recommendations for sustainable urban traffic management include; Improve the design of road networks and make the streets smooth and wide, improved pedestrian and cycling network designs which are cost effective, parking management solutions, enforce public transport policies, road accident detention and prevention, designing clear, safe and frequent crossing points, proper and clear road signals and working traffic lights, use of rounder about to reduce traffic jams and collision at intersections.

Aworemi (2009) suggested the following congestion reduction strategy: Enhanced Transport Coordination: the various modes of public transport including intermediate public transport have to work in tandem. They should complement rather than involve themselves in cutthroat competition. Therefore, there is an urgent need for a transportation system that is seamlessly integrated across all modes in Lagos state. Since the ultimate objective is to provide an adequate and efficient transport system, there is a need to have a coordinating authority with the assigned role of coordinating the operations of various modes. This coordinating authority may be appointed by the state or federal government and may have representatives from various stakeholders such as private taxi operators, bus operators, railways and the government. The key objective should be to attain the integration of different modes of transport to improve the efficiency of service delivery and comfort for commuters, which in turn can dissuade the private car owners from using their vehicles and thereby reducing the number of cars on the roads that eventually lead to congestion reduction.

Road Capacity Expansion: road widening is often advocated as ways to reduce traffic congestion. However, it tends to be expensive and may provide only modest congestion reduction benefits at the long run, since a significant portion of added capacity is often filled with induced peak period vehicle traffic. A large amount of additional capacity would be needed to reduce urban traffic congestion. Roadway capacity expansion provides only slight reductions in urban traffic congestion.

Transport System Management: Transportation system management (TSM) is a term used to describe a wide range of measures and techniques that attempt to both maximize the capacity of the street system and reduce the demand on it.

Some traffic management techniques that can be used to combat traffic congestion are listed below:

Junction improvement, grade separation using bridges (or tunnels) freeing movements from having to stop for other crossing movement, reversible lanes, where certain sections of highway operate in the opposite direction on different times of the day or days of the week, to match asymmetric demand. This may be controlled by variable message signs or by movable physical separation, preferential treatment for High Occupancy Vehicle (HOV), i.e. Bus lanes e.g. Bus Rapid Transit (BRT), separate lanes for specific user groups ( usually with the goal of higher people throughout with fewer vehicles), traffic calming measures such as traffic bumps etc, improved traffic signs/lane marking, etc, supply and demand: congestion can be reduced by either increasing road capacity (supply) or by reducing traffic (demand). Capacity can be increased in a number of ways, but needs to take account of latent demand otherwise it may be used more strongly than anticipated. Increased supply can include, adding more capacity over the whole of a route or a bottlenecks, creating new routes, and traffic management improvement. Reduction of demand can include, parking restriction, park and ride, reduction of road capacity, congestion pricing, road space rationing, and incentives to use public transport, telecommuting, and online shopping.

Business Cost of Traffic Congestion

There is evidence that business views traffic congestion as causing a serious problem. The belief is that it causes a significant cost imposition. A survey from the United Kingdom found that traffic congestion was perceived as the most important factor likely to affect costs and service in the next three years (Fernie, and Marchant, 2000).A large number of transport economics studies focus on the time component of commuting costs (Smalland Verhoef, 2007). Estimates of the time component of commuting costs vary by a large margin, but studies tend to find that the value of travel time is 20% to 100% of the hourly (gross) wage (Small, 1992). De Borgerand Fosgerau (2008) find strong reference- point effects in stated preference data and suggest a way to correct for this effect. Revealed preference studies tend to find substantially higher values than stated preference studies. Although the time component is an important part of the commuting costs, the other components are not negligible, and may therefore not be ignored (Cogan, 1981).For commuters, the monetary costs are thought to be about 30% to 40% of the time costs (e.g., Fujita, 1989; Small, 1992). Furthermore, workers may vary the speed of their commute through their choice of travel mode, so the share of the time costs as part of the total commuting costs is endogenously determined. As a consequence, information on the costs of the time component is not necessarily informative about the total commuting costs.

For all travel modes except car use, the marginal monetary costs are easy to determine. For non-motorized transport (bicycling, walking), the marginal monetary costs are (close to) zero; for public transport (train, bus, metro), the marginal monetary costs can be derived from the price paid for the ticket. For car users, however, who are the majority of commuters, the marginal monetary costs associated with commuting are not so straightforward to determine. These costs of car use comprise not only the variable costs of car use (fuel, depreciation of the car due to its use), but also costs that are related to the ownership of the car (interest, insurance, etc). The latter cost component is frequently treated as fixed, and it is therefore assumed not to affect workers' marginal

costs of travel. This may be argued to be a relevant assumption in the United States, where car availability is high and almost all workers commute by car. Outside the United States, the proportion of workers who commute by car is much smaller. For example in the Netherlands, approximately 50% of workers commute by car. Car ownership decisions will frequently depend on the length of the commuting distance, which constitutes about one third of a car's mileage (DeJong, 1990). Consequently, even though treating car ownership costs as fixed may make sense with respect to some travel decisions, these costs are clearly not fixed with respect to commuting. Workers’ marginal commuting costs can be derived in various ways. One method, familiar to labour economists, is to use the tradeoff between wages and the length of the commute, using hedonic wage models, as developed by Rosen (1986). But such a method has a number of disadvantages, as it relies on the (implicit) assumption that workers have full information about availability of jobs and do not have to search for jobs (Hwang et al., 1998; Gronberg and Reed, 1994). A number of studies have shown that estimates of valuation of job attributes, such as commuting time, are likely seriously downward biased if hedonic wage models are used (Van Ommeren et al., 2000; Villanueva, 2007).

Traffic Management

The term “traffic management” comprises a variety of techniques for dealing with highway and traffic – related issues. As a concept, it is a process for planning and operating a system of urban highway and street network. It arises from the need to maximize the capacity of existing high way networks with a minimum of new construction. More recently, the emphasis of the process has spanned beyond simple capacity improvements to accident reduction, demand restraint, public transport priority, environmental improvement and restoring the ability to move around safely and freely on foot and by pedal cycle. Thus traffic management may be considered as a means of optimizing the available highway network in accord with specified objectives as dictated by the prevailing local issues (Adebisi, 2004).Traffic management according to Adebisi (2004) involves a package of actions designed to optimize the available highway network in a well focused manner. The package of actions comprises a variety of techniques for dealing with traffic and highway related issues. In general terms, the main features of traffic management measures may be summarized as: Be relatively inexpensive and be amenable to early implementation, Improved the usefulness of existing facilities while duly accommodating the different requirements of the different categories of road users, Improve safety or, and a minimum, maintain the existing level of safety, Protect the environment, improving it where possible.

Among the relatively inexpensive techniques available for developing comprehensive traffic management proposals are: Road capacity enhancement schemes, Traffic sign (i.e. pavement, markings, road sign, etc.), Guardrails, cross markings etc, Traffic calming, Vehicle parking regulations and controls, Pedestrianisation measure, Accident reduction programs, Bus priority measures, Application of intelligent traffic systems (ITS).

Any traffic management scheme involves a compromise as different categories of road users have different and sometimes, conflicting requirements. Consequently, surveys should be undertaken prior to introduction of any scheme. Avenues for feedback and appropriate revisions of strategies should also be institutionalized through constant monitoring. More detailed information on traffic management is available in current literature on the subject such as Salter (1996), Slinn et al (1998) and Asheley(1994).

Traffic Generation and Attraction

It has been acknowledged that the typical Nigerian urban problems concerning land use and transportation revolve around many social, political, cultural, economic, technical and environmental issues, within the context of which future land use and traffic projections can be made. Abler, Adams and Gould (1972) acknowledged this fact when they stated that land use analysis is a convenient way to study the activities that provide the basis for trip generation because travel pattern (routes and flows) are directed by network structure and land use arrangement.

Blunden (1972) also related transportation pattern to the route network characteristics. He stated that traffic is a medium of activity. It is a joint consequence of land use potential and transport capability. If land use and transport do exist, the traffic that thereby evolves is a result of these two factors. Land use pattern on the Lagos metropolis to a great extent influences the traffic situation there. This is true because the routes on the northern, central and eastern portion of Lagos metropolis area which is characterized by agreat concentration of residential and commercial activities as well asinstitutional activities have a heavier flow of traffic than those on the western portion of Lagos State. In 2002, when a survey of Lagos urban traffic was conducted, thetraffic situation at different times of the day by different modes of transportreveals an ever-increasing vehicular traffic.

According to Oni (2004), the huge traffic generated between these various areas on the one hand, and residential districts on the other, is one of the main sources of congestion. Another major cause is the traffic between the city and almost the whole of the Nigeria country side. The city’s traffic hinterland even extends to parts of neighboring countries such as Benin Republic, Niger and Chad for which Lagos acts as an entry port. The traffic is handled mainly by trailers, oil tankers, buses, trucks and other cars: since the Nigerian railway and Lagos public ferry services had dwindled. The whole load has been shifted to cars and vans thereby congesting the roads the more.

2.2 Conceptual Framework

Traffic Congestion Theories

Traffic Flow Theory

According to Wikipedia Traffic flow is the study of interactions between vehicles, drivers, and infrastructure (including highways, signage, and traffic control devices), with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems. In a free-flowing network, traffic flow theory refers to the traffic stream variables of speed, flow, and concentration. These relationship are mainly concerned with uninterrupted traffic flow, primarily found on freeways or expressways. Lieu (1999), Flow conditions are considered “free” when less than 12 vehicles per mile are on a road. “Stable” is sometimes described as 12-30 vehicles per mile lane. As the density reaches the maximum flow rate (or flux) and exceeds the optimum density (above 30 vehicles per mile), traffic flow becomes unstable, and even a minor incident can result in persistent stop-and-go driving conditions. “Breakdown” condition occurs when traffic becomes unstable and exceeds 67 vehicles per mile. Rijn, (2014) “Jam density” refers to extreme traffic density associated with completely stopped traffic flow, usually in the range of 185-250 vehicles per mile per lane.

There are common spatiotemporal empirical features of traffic congestion that are qualitatively the same for different highways in different countries measured during years of traffic observations. Some of these common features of traffic congestion define synchronized flow and wide moving jam traffic phases of congested traffic in Kerner’s three-phase traffic theory of traffic flow.

Alber (1997) explain that traffic flow can be divided into two primary types are:

Uninterrupted flow, interrupted flow, uninterrupted Flow

This is a way of flow regulated by vehicle-vehicle interaction and interaction between vehicle and the roadway. Vehicle traveling on inter-state highway participate in uninterrupted flow. Contrary to this, there exist interrupted in traffic flow on our inter-state highways.

Interrupted flow is regulated by an external means such as traffic signals etc. Under interrupted flow conditions, vehicle – vehicle interaction play a secondary role in defining the traffic flow. Vehicle traveling on intra-urban roads participate in interrupted flow.

Kerner’s Three-Phase Traffic Theory of Traffic Flow

Kerner’s Three-Phase Traffic Theory was developed by Boris Kerner between 1996 and 2002 according to (Lieu 2005 and Goa 2007). It focuses mainly on the explanation of the physics of traffic breakdown and resulting congested traffic on highways. Kerner describes three phases of traffic, while the classical theories based on the fundamental diagram of traffic flow have two phase: free flow and congested traffic. Kerner’s theory divides congested traffic into two distinct phases, synchronized flow and wide moving jam, bringing the total number of phases to three:

Free flow (F), wide moving jam (J), synchronized flow (S), free Flow (F).

In free traffic flow, empirical data show a positive correlation between the flow rate (in vehicles per unit time) and vehicle density (in vehicles per unit distance). This relationship stops at the maximum free flow with a corresponding critical density.

Wide Moving Jam (J)

A moving jam will be called “wide” if its length (in direction of the flow) clearly exceeds the length of the jam fronts. The average vehicles speed within wide moving jams is much lower than the average speed in free flow. At the downstream front the vehicles accelerate to the free flow speed. At the upstream jam front the vehicles come from free flow or synchronized flow and must reduce their speed. In contrast to wide moving jams, both the flow rate and vehicle speed may vary significantly in the synchronized flow phase. The downstream front of synchronized flow is often spatially fixed, normally at a bottleneck at a certain road location. The flow rate in this phase could remain similar to the one in free flow, even if the vehicle speeds are sharply reduced.

Edward Ullman (1956) offered explanation for the factor which affect transport development in any locality and has been generally acclaimed as the best. He sigh the three variables of: Regional complementarity, Intervening opportunity, Spatial transferability

In Regional complementarity he relied on the theory of comparative advantage or real differentiation in the ability of resources between region/localities whereby they are able to produce different goods end, or services. It is usually that a certain may have and exercise greater advantage than the other in the process of producing these specific goods and services thus leading to a declaration of boom or surpass in one a deficit or recession in the other man explained this spatial phenomenon to be the basis for spatial interaction between two areas in other words, a supply and demand indices roust be established. Therefore it is the complementarity of supply and demand that brings about movement and interactions.

In traffic congestion studies, this underlies the reason which prompt people to move from their settlement which generates such traffics area to area traffic attractors. It is evident that at ‘peak’ hours the traffic is highly intensified this leading to a situation where the demand functionaries exerts excess pressure upon the supply components of road networks and facilities thus leading to congestions. The concept of intervening opportunity is the occurrence of alternative supply indications between two regions involve in spatial interaction. If the alternative resource is nearer to the source of demand and offering the same or similar opportunity in supply, then the demand factors would move to the new location and abandon the old. It is the degree of the intervention of the alternative source which will certainly determine the level of spatial interactions between the two areas and therefore the supply and demand of transport for the purpose.

Spatial Transferability concept refers to the constraints imposed on the movement of goods & distance. The indices are measured in time and money costs, Wherever the costs are too high. Interaction will greatly and drastically reduce. It can even extinct some routes of intervening opportunities.

The Queue Theory

For the purpose of queuing theory, a queuing can be defined as the aggregation of items awaiting service. Queue may consist of any discrete items including people, motor vehicles, telephone calls, airplanes. Queuing everyday is a case construction of models to reflect various types of queuing systems. From this model prediction can be made about how the system can cope with the various demands made upon it. Generally a situation of queue arises when the rate of arrival of items requiring service is greater than the rate of service ( i.e when the number of vehicles on the road is more than the infrastructure). Queuing theory can be applicable to many instances e.g vehicles awaiting indications from Traffic lights, shop counters, toll gates operators on a highway, telephone exchanges etc. Thus in any situation where there is a bottle neck the queuing theory is applicable.

Arrivals, Queue, Service, Outlet/Exit

Arrival is concerned with how items arrive at the system or the rate at which they arrive and time gap between them. Queue refers to what happens in the system between the arrival of an item requiring service and the time. The service was carried out. Service means the time taken to service an item in the system.

Outlet is the final exit from the system. Time in the system is taken to mean the queuing time plus the service time.