Economics Of Overloading And The Effect Of Weight Enforcement

In this study, focus has been places on the relationship between economical effect of overloading and weight enforcement. Strathman (2001) studied the economic rationale of vehicle overloading activities when they face weight enforcement. The study shows that both the intensity of weight enforcement and the level of penalty can deter overloading activities. The patterns of weight enforcement practices by authorities combine different levels of enforcement and penalties. As a result, the response of overloading activities depends on these two factors. Two perspectives of weight enforcement are being analysed which includes:

1. Low penalties with extensive enforcement
2. High penalties with relatively low levels of enforcement

The fourth power rule has an important role in road damage and cost estimation which includes annual budget for maintenance and user cost design. Johnson (2004) investigated the Fourth Power Rule in a computable equilibrium model of Sweden, whose study scope was the effect on road wear and deformation to the Fourth Power Rule. Recent techniques of prediction are observed in the study by applying the chaos theory in the field of road traffic. Frazier and Kockelman (January, 2004) analyzed traffic flow data and found it chaotic. Van Zuylen (1999) discussed the implications of human behaviour, chaos, and unpredictability for urban and transportation planning as well as forecasting. Chaotic behaviour in traffic can be caused by delays in human reaction. Nair et al( 2001) analyzed traffic flow data and characterized it as a chaotic factor and demonstrated how random-utility based models of relatively simple social behaviours produced chaotic behaviour and offer a detailed application of chaos to traffic flow. After evaluating the presence of chaos, analytical process has been done based on two methods of time series prediction and the concept of chaos theory. Simple exponential smoothing is corresponding to the chaos theory with time span 1 day, and moving average method corresponding to the chaos theory considering time spans 3, 5, and 7 days as well as data for vehicles axle loads that are collected prior to the time period of this case study.

Delimitation

This study focuses on the effects of overloading on TNPA roads and excludes data and emphasis on the national road network. Other road deterioration factors have also been excluded from the study such as paved roads - involving both asphalt and concrete - which carry the bulk of road traffic, deteriorate for a number of reasons and therefore require routine maintenance on a regular basis. For example, sunlight causes a continuous, slow hardening action on bituminous surfaces, while the penetration of water into and from under (poor drainage) road pavement layers can lead to a loss of load-bearing capacity and consequent increased rate of road structure deformation. Research has shown, however, that light vehicles such as cars and light commercial vehicles, make a relatively small contribution to the structural damage of a road pavement compared to that of heavy vehicles.

Furthermore, the load carried by each heavy vehicle axle determines its destructive effect. The degree of damage caused to roads by over- or under-inflated tyres can be as much as or even more than the degree of damage caused by overloaded heavy vehicles with correctly inflated tyres. It is thus essential that tyres be inflated according to the manufacturer’s specifications for optimum load/inflation pressure, and that the legal axle load limits for roads and bridges, as governed by the axle load regulations, should be complied with. This will result in improved longevity of the road infrastructure, tyres and the heavy vehicles that use the road. The concept of accurate tyre pressure will be excluded due to time restraints.

Overview and Research Design Methods

In this study, 3 main points have been identified. Overloaded vehicle traffic is an inevitable outcome due to rapid economic growth in South Africa. All developing countries will have to endure this problem until development becomes stabilized. Overloading is a unique problem as it cannot be totally eliminated as evidence provides that even developed countries such as USA and the UK still experience overloading between 2 – 5 percent. (Strathman. 2001. Page 1). An effective means of control is through monitoring, legislation and education. Developing countries such as South Africa lack sufficient funding and technology to promote this however developed countries such as USA invest a great deal in road safety campaigns and policy enforcement. If overloading can be controlled overloading properly, we can easily extend the lifespan further. The key objective of this research is to identify the major impacts of overloading and therefore establish recommendations to minimize the occurrences. The reasons for overloading will be carefully scrutinized as well as the responsible transgressors. Economic costs are a key variable in terms of maintenance of roads will be used to determine the extent of the road damage. This study is classified as a non empirical research based on previous overloading studies, weighbridge data and interviews with key logistics role players at the main areas of TNPA. As the study looks at primary factors of overloading therefore the research will be of an exploratory nature.

Division of Chapters

In chapter one, a brief introduction and background to the overloading phenomenon is introduced. The questions that are put forward are carefully thought of to investigate and meet the objectives of the study. These objectives will identify appropriate ways to minimize the effects of overloading and determine efficient solutions by analyzing theories based on other studies. A literature review will be followed in Chapter two discussing atleast three theories to identify the impacts of overloading on TNPA roads.

Conclusion

Overloading is a major safety issue, an operating cost issue, and a risk management issue. Signs of overloading include a sagging rear-end; premature brake wear, irregular tyre wear; and loose, unresponsive steering and suspension. Vehicle and fleet owners should be proactive in ensuring their vehicles are not overloaded in order to get the best long-term use from their vehicles to reduce their risk and protect the interests of drivers, clients and other road users. Overload control helps us to achieve what we call asset preservation. If overloading is reduced, road infrastructure will be preserved and prolong its lifespan.

Literature Review

Introduction Overloaded trucks cause serious damage to roads. The maximum load that a truck can carry is 56 tons. If a truck is overloaded to 60 tons, for example, a single trip can do more damage to the road than a few thousand cars. The latest research conducted by the CSIR (2007, page 1) shows that overloading cause about 5 billion Rand damage to the national road network The objective of this research is to:

1. To determine the amount of economic loss due to overloaded heavy vehicle traffic. Axle loads will be used to calculate the total equivalent axle load and therefore used to determine the total road lifespan.
2. To find ways to effectively identify the truck overloaded by axle load survey.
3. To collect information based on previous maintenance cost of the particular study area (Transnet National Port Authority roads).
4. To minimize the impact of truck overloading.

It is essential for TNPA to avoid this cost if there is proper law enforcement and proper load controls. Overload control help to achieve asset preservation.

Overview of Main Theories

Theory One: Chaos Theory - Pavement management is an important issue, according to its maintenance and repairing roads surface expenses. Heavy vehicles axle loads are considered as the most important factor of road destruction. Based on observed researches in the literature, the damage on roads surface is related to the vehicles axle loads by a nonlinear acceleration rate mainly in a polynomial equation of forth degree. Truck weighing control is made by certain equipments, incorporating static, dynamic, and portable scales. Different axle loads and limitations in the scope of case study are shown which include three most popular axle group configurations. They include 3 axle-10 wheels, 5 axle-12 wheels, and 5 axle-18 wheels trucks. Maximum axle loads are different from different configurations; however, it does not seem necessary if the total weigh is equal to the sum of axle load limitations. Truck axle loads are checked in weighing stations by random and if they exceed the authorized limit, overloaded trucks would be stopped afterwards, requiring the loads adjusted based on regulations.

Time Series Prediction

Moving Average. Moving average method of prediction is obtained by first taking the average of the first subset. The fixed subset size is then shifted forward, creating a new subset of numbers, which is averaged.

Exponential Smoothing. Exponential smoothing is either applied to time series data, or to produce smoothing data for which the time series are sequence of observationsTheory Two: Fourth Power Rule - An increase in axle weight generally causes a more than proportional increase in road damage. The relationship appears to approximate an exponential function, and various studies have assumed the power of the exponent to be about 4 as a rule. Estimates of the exponent’s power vary substantially. The “fourth-power” rule emerged from road tests conducted in the 1950s by the organization now known as AASHTO, the American Association of State Highway and Transportation Officials. The tests involved subjecting a number of road structures to alternative axle loads and configurations, and then measuring the resulting damage.

For each type of pavement a load equivalence factor that varies by axle configuration and axle weight. The load equivalence factor expresses the pavement damage relative to that from an 18ton single axle. Analysis of the variation in these factors by axle weight led to the fourth-power “rule,” which is actually a rough generalization. Studies of pavement damage from traffic have used a variety of methods. In addition to full-scale road tests like those conducted by AASHTO—which are time consuming and expensive—studies have used accelerated pavement testing devices and computer simulations. By passing a vehicle over a short stretch of pavement in rapid succession, an accelerated device enables 20 years of serviceability loss to be obtained in several weeks or months.

Theory Three: Analysis Cost of Loss of Road distress due to Overloading

This theory is used to calculate the road distress loss cost resulting from overloading and therefore the amount of loss cost that TNPA shall bear can be determined. The presence of overloading is indicated by the width area of rutting which is more than 60% of total road structural distress per kilometer. The loss cost of road distress due to overloading is calculated based on damage factor (DF) and deficient design life (DDL). The loss cost of the overload vehicle user shall bear is 60% of total deficit factor cost (DFC) and deficit design life cost (DDLC), considering that not all road structural distresses are caused by overloading freight transport. Road distress caused by vehicle weight and passage is stated in Equivalent Single Axle Load (ESAL) that is the amount of single axle passage of (8160 kg) which possibly causes the same distress level of the axle load passes through. The formulae of ESAL are categorized by axle types (single, tandem or tridem axle). ESAL is also called as damage factor (DF) value caused by overloading heavy vehicles. One of the impacts resulting from overloading is the increase in equivalent number.