Department of Civil Engineering
Permanent URI for this community
Browse
Browsing Department of Civil Engineering by browse.metadata.advisor "Bester, C. J."
Now showing 1 - 18 of 18
Results Per Page
Sort Options
- ItemThe analysis of road traffic accident data in the implementation of road safety remedial programmes(Stellenbosch : Stellenbosch University, 2001-03) Mollet, C. J.; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: A road safety remedial programme has as an objective the improvement of road transportation safety by applying road safety engineering remedial measures to hazardous road network elements in a manner that will be economically efficient. Since accident data is the primary manifestation of poor safety levels it must be analysed in manner that will support the overall objective of economic efficiency. Three steps in the process of implementing a road safety remedial programme, that rely on the systematic analysis of accident data, are the identification of hazardous locations, the ranking of hazardous locations and the evaluation of remedial measure effectiveness. The efficiency of a road safety remedial programme can be enhanced by using appropriate methodologies to measure safety, identify and rank hazardous locations and to determine the effectiveness of road safety remedial measures. There are a number of methodologies available to perform these tasks, although some perform much better than other. Methodologies based on the Empirical Bayesian approach generally provide better results than the Conventional methods. Bayesian methodologies are not often used in South Africa. To do so would require the additional training of students and engineering professionals as well as more research by tertiary and other research institutions. The efficiency of a road safety remedial programme can be compromised by using poor quality accident data. In South Africa the quality of accident data is generally poor and should more attention be given to the proper management and control of accident data. This thesis will report on, investigate and evaluate Bayesian and Conventional accident data analysis methodologies.
- ItemA computerised decision support system for the implementation of strategic logistics management optimisation principles in the planning and operation of integrated urban public transport(Stellenbosch : Stellenbosch University, 2001-12) Duff-Riddell, W. R. (Wayne Russell); Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Public and private transport system planning and operation have tended to be fragmented functions. In particular, public transport is often planned and operated independently of the "private" transport system. South African government policy now requires that comprehensive, strategic transport plans be prepared by metropolitan transport authorities. These plans are expected to conform to national strategic objectives as well as including local current and longterm objectives. This planning is required in the environment of a multi-modal, multi-operator, public-private partnership scenario that is new for most of the role players. The lack of experience is accompanied by a lack of any existing model for dealing with this scenario. This dissertation describes such a model. The model is based on the principles of strategic logistics management commonly employed in commerce and industry, including service-oriented industries. The modelling process is thus based on achieving a combination of customer service and long-term objectives. The model comprises a number of separate components and steps: • A transport network model (Emme/2). ~ A multi-class, generalised-cost assignment of private and public transport demand onto a network, modified to be modeless to the public transport users, is performed. This assignment allows for the imposition of generalised-cost reflecting urban-planning objectives in addition to more conventional costs such as travel cost. In this assignment, the interaction of public and private transport is accounted for and results in an associated modal choice. ~ A series of single-class generalised-cost assignments is then used to "focus" public transport demand to create corridors of demand adequate to justify public transport routes. This process can be enhanced to develop a design promoting switching from private to public transport. It also allows for multi-period route design. ~ The results of this modelling process are output to a text file and then subject to the processes described below. The results of these processes are then input into the network model where a standard transit assignment is performed and used to modify the proposed lines and update the network design data with respect to boardings and alightings at nodes. This information is used to design fixed infrastructure. • A Microsoft Access database and route extraction program. );> The network model data is drawn into the database where it is subject to a route extraction program that converts the assignment results from the network model into a set of mode specific potential public transport route definitions. These route definitions are based on paths of maximum demand. The extraction process is controlled by parameters specified by the planner, such as minimum route lengths and the demand level for various categories of service. );> After route extraction, vehicle allocation, and transit assignment, the database provides details of the boardings and alightings and number and details of transit lines using each node and link in the network. This data is used to design fixed infrastructure. • A Microsoft Excel spreadsheet vehicle operating cost model. );> For each vehicle type, the operating cost given the anticipated vehicle mileage and operating speed is determined. This is used to guide the choice of vehicles for different routes. • A Lingo goal-programming model. );> The potential routes and the available or potential fleet are subjected to a goalprogramme in which the optimum choice of vehicle allocation is determined. The allocation parameters can be controlled by the planner. These parameters may include costs, energy, fuel consumption, and vehicle and route limitations amongst others. Multiperiod design is included in the modelling process so that the optimum design may be for the operating period, daily, or weekly cycle. The modelling process provides two main outputs: • A set of fully described and costed transit lines ill terms of both routing and vehicle allocation. These transit line definitions can be output to the level of driver instructions if necessary. • Details of the type and location of infrastructure to be provided on the network.
- ItemThe economic evaluation of bus and minibus taxi terminals and transfer facilities(Stellenbosch : University of Stellenbosch, 1998-12) Pienaar, Wessel Johannes; Bester, C. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The dissertation describes the functions of bus and minibus taxi terminals and transfer facilities. Planning, design and evaluation guidelines are proposed. These proposals are aimed at the following aspects: the geometric features and functional layout of facilities in order to enhance the effective usage thereof by passengers, as well as the smooth flow of vehicles; the location of facilities and traffic control arrangements, which take cognisance of effective traffic flow as well as acceptable walking distance by commuters; and an evaluation methodology which addresses allocative efficiency from an economic viewpoint, supplemented by analysis guidelines which consider distributive efficiency from a viewpoint of equitable distribution of welfare. It is explained how benefits for travellers, the transit operator and the subsidizing authority, and the opportunity costs of supplying the facility can be determined. A model is proposed whereby the non-monetary component of generalised travel costs can be estimated. The use of economic evaluation techniques for the selection and prioritisation of projects is detailed. This is supplemented by an example of an economic evaluation of a proposed bus/minibus taxi terminal. Subsequently it is examined how the design and effectiveness of a real world passenger transport terminal could be affected by the use of the guidelines proposed in the dissertation. The dissertation, lastly, deals with welfare distribution and the more equitable community accessibility and mobility which can be brought about by the creation and use of passenger transport terminals and transfer facilities. Also discussed is the accommodation of welfare distribution with an economic evaluation as a means of achieving greater equity or fairness and the ways in which this can be done.
- ItemEmpirical study of heavy vehicle operating speeds on mountainous downgrades in the Western Cape, South Africa(Stellenbosch : Stellenbosch University, 2016-03) Oncke, Jandre; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Heavy vehicles play a major role in the economic well-being of a country through its significant role in moving freight. Therefore any adverse effect to the road freight, from being stuck in traffic to being involved in a fatal accident, will have negative impacts on the economy and on the safety of the persons involved. Therefore it is paramount to understand how and to what extent factors such as road geometrics, vehicle characteristics and weather conditions affect the safety of heavy vehicles. There are several countermeasures addressing the issue, with the most common approach being to supply drivers with better information. This is done through the use of a grade severity rating system (GSRS) or weight specific signs (WSS) that direct heavy vehicle drivers to adopt a slower and more suited speed for the relevant downgrade. However, there are no such countermeasure or system deployed in South Africa, and simply adapting the current GSRS and WSS might not suffice, since most of these models are outdated and does not account for newer technology or regulations. Thus, this research paper aimed to gain a better understanding of how the select geometric and vehicle characteristics influence the operating speed of heavy vehicles on downgrades, and ultimately to formulate a mathematical equation that can be used to estimate the operating speed of heavy vehicles on downgrades. The equations can be used to design WSS for South African mountain passes. The variables that have been identified as important in this study include, operating speed, gross vehicle mass, gradient, downgrade length, curve radius, superelevation and stopping distance. The operating speed is taken as the dependent variable and measure of safety, since it is the most common relatable variable among the diverse and complex nature of heavy vehicle operating systems. In order to collect data of the select variables, the critical section for each mountain pass was identified. This was done by following descending heavy vehicles and determining the relevant speed profiles. This was done multiple times for each pass, so that a combination graph could be obtained, which was analysed to identify the critical section. Data for the variables were collected using various devices and means. The operating speed and number of axles were collected by video recordings, and gradient, downgrade length and curved radius were collected with instruments such as a GPS and theodolite. The mass of the heavy vehicles were obtained from the weighbridges situated along routes of the relevant mountain passes. Analysing the data were primarily done through regressing the data, with the calculated operating speed through the critical sections as the dependent variable. Three regressions were done, namely a general regression, regression with a change in horizontal alignment and a regression with a compulsory stop at the base of the downgrade. Equations were found for heavy vehicle speeds on steep downgrades in general and on downgrades that subject operating speed to small curve radii. A logical exercise was also done, in which it was attempted to determine driver familiarity with the select downgrades. It was found that only half of all the observed heavy vehicle drivers exhibited familiarity with the given pass. Based on the finding that more relevant information is needed by the drivers and the lack of a sufficient means of conveying information to heavy vehicle drivers, it is fitting that an improved alternate to the GS 505 signs be found. The two equations found in this study can be used to this end.
- ItemEstablishing and applying speed-flow relationships for traffic on rural two-lane two- way highways in the Western Cape(Stellenbosch : Stellenbosch University, 2013-12) Twagirimana, Janvier; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Speed-flow-density relationships are the most useful tools in the highway design and planning process. They are useful in predicting the roadway capacity, in determining the adequate level-of-service of traffic flow and in determining travel time for a given roadway. Two-lane two-way rural highways constitute the vast majority of the rural road network in South Africa. Nowadays in the Western Cape and other provinces of South Africa, the speed-flow-density relationships normally used for rural transportation studies are derived from the Highway Capacity Manual, which reflects the traffic conditions in the North American situation. Since the North American traffic conditions may be different from the South African conditions, a need to investigate speed-flow-density relationships on these highways in South Africa arises in order to justify any investment made on these roads. In this context, a video technique was used to collect traffic flow data during morning peak hours on two rural two-lane two-way highways in the Western Cape Province in order to investigate these relationships. Through the use of Adobe premiere C.S 6 software, travel time of individual vehicles and distance headways were measured and used in computation of average speed and average density. Several researchers have developed models to describe the relationships between traffic characteristics on uninterrupted flow facilities. In this study, some of these models were tested using collected data in order to investigate which model fits the data satisfactorily. Statistical methods were used to evaluate the ability of each model to predict the flow characteristics over the whole range of data. Average speed and density data were used through regression analysis to perform curve fitting and testing of these developed models. In the next stage, the model which provided a best representation of the data on each section was selected and through the application of the steady-state equation (2.1), flow-density and speed-flow relationships were established on these sections. The available data were also used to investigate the impact the observation time has on the speed-flow curve and the resulting capacity value. Finally, the developed speed-flow curves were used to determine the capacities of the study sections. These capacity values were used to determine if the shoulder usage contributes in increasing the capacity of two-lane two-way highways by comparing them to the capacity provided by HCM.
- ItemEstablishing and applying speed-flow relationships for traffic on South African freeways(Stellenbosch : Stellenbosch University, 2001-12) Roux, Jacques; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Peak mornmg traffic-flow data were obtained from video footage of three representative freeway sections on the Nl and N2 westbound towards Cape Town. Flow, speed, and density measurements were made from the footage with the aid of a stopwatch. Many researchers (2-12) have originated and developed models to describe the relationships between traffic flow characteristics (speed, flow, and density) on freeways. In this report, a number of these models have been investigated with data obtained from South African freeways. The ability of each model to predict flow parameters over the entire range of data was evaluated with the aid of statistical methods. The tests were performed by regressing average speed vs. average density. Flow-density and speed-flow relationships were derived through application of the steady-state equation (2.6). In each case, a final model was chosen through visual inspection that consisted of two separate curves, one for the uncongested flow regime and one for the congested flow regime. Furthermore, speed-flow relationships were examined for individual lanes and compared to relationships established for average lanes. The models were also compared to models obtained from overseas studies (1,16,19) as well as from studies done locally (17). A secondary objective of this study is to investigate the performance of existing freeway facilities through application of the relevant models to the traffic-flow data of a particular facility. The current peak-morning performance of the N2 freeway section is investigated in terms of travel-time and travel cost. The particular study section consists of three lanes, the right hand lane being an HOY lane dedicated to taxis and buses. Different hypothetical cases are investigated. The first hypothetical case is an investigation into the traffic situation on the freeway section without the influence of the HOY lane. The second hypothetical case investigates the traffic situation on the section with perfect operation of the HOY lane. The current performance of the N2 section is compared to the performance of each of the hypothetical cases.
- ItemInvestigating fatal road accident data(Stellenbosch : Stellenbosch University, 2007-03) Van Niekerk, Andri; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: This thesis concerns the investigation of four analyses techniques in terms of their utility and adequacy for analyzing fatal road accident data in South Africa. PROBLEM DEFINITION: Road accident data are summarized annually in various forms, but the relationships between the different categorical variables are not determined. The study aimed to address this problem. Road accident rates are published in order to compare year-to-year change in an accident rate. It was necessary to investigate a method to determine whether these year-to-year changes are statistically significant and whether there should necessarily be a reason for concern when an increase in accident rate is detected. Multiple regression models also including qualitative variables were investigated in this study. ACCIDENT DATA AND ANALYSIS TECHNIQUES: Road accident data were found available in the format of a MS Access database which could be manually investigated. Traffic and speed data were readily available from Mikros Traffic Monitoring (Pty) Ltd in the form of SANRAL's CTO Yearbooks and was found to be reliable and sufficiently detailed. Any road geometric data were omitted from the study due to insufficient detail available. All data were found to show levels of poor data quality. Certain variables were thus omitted from the study e.g. the age group variable. The fatal road accident database was analysed using Correspondence Analysis and Association Rules (for analyses of the categorical variables) and, the application of the Poisson distribution for chance variation analyses and Multiple Regression Analyses (for the continuous variables). METHODOLOGY: Fatal road accident data were gathered by performing queries in the fatal road accident database. Traffic and Speed data were gathered by manually investigating the SANRAL CTO Yearbooks and manipulating the data to be integrated with the fatal road accident database. After all data manipulation was completed, the four analyses techniques mentioned above were applied using the software package Statistica. FINDINGS: Correspondence Analysis and Association Rules were found to be adequate for analysing categorical road accident data variables with some data quality limitations and insufficient data sampling. The time period used for chance variation analysis was too short to deliver significant results. Three multiple regression models were created with one of the models being able to predict the number of fatalities per fatal accident with k equal to approximately 40%. CONCLUSIONS AND RECOMMENDATIONS: The following conclusions are drawn and recommendations are made based on the findings of this study: ~ Detailed and quality road accident data for South Africa is unavailable. Better quality data are urgently needed for the purpose of analysis. ~ Correspondence Analysis is found to be the most appropriate technique for road accident data analysis and should be applied on an annual basis. ~ Association Rules Analysis results are influenced by small sample sizes and too many unknown variable categories. Larger sample sizes and exclusion of the unknown categories might improve the results. ~ The analysis period for chance variation is too short and a longer period will provide more significant results. ~ The multiple regression model predicting the number of fatalities per fatal accident is accepted in terms of utility and adequacy.
- ItemLand-use transport strategies to cope with suburbanisation(Stellenbosch : Stellenbosch University, 2002-12) Van Zyl, N. J. W.; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Suburbanisation is a world-wide phenomenon and is characterised by the decline of central business districts and accelerated growth of commercial activities in the suburbs. The impact of suburbanisation is wide-spread and multi-dimensional, affecting the whole urban system in terms of its structure, activity and transport patterns. In South Africa, suburbanisation, together with the impact of the former group areas policy, has made suburban developments less accessible to the low-income groups living on the edges of the metropolitan area. Planners have proposed various urban densification strategies for the rather unique problems of the spatially inefficient South African cities, including corridor development along main public transport routes and the development of activity nodes. In order to implement these urban densification strategies successfully, it is important to understand the locational choice behaviour of business managers, and the factors that will attract them to locate in a certain area. This will enable metropolitan authorities to evaluate and implement the best policies to promote development of priority corridors and nodes The research for this dissertation was motivated by the extensive problems of suburbanisation, the lack of knowledge on the relative impact of land-use transport factors on the locational choices of businesses, and the apparent limited application of stated preference (SP) survey techniques and discrete choice models to spatial choices of businesses for urban planning purposes. The main objectives of the research were to determine the locational choice behaviour of retail businesses in strategic spatial terms, and how this knowledge can best be used to manage suburbanisation. The dissertation reviews intemational and South African studies on the planning and policies of the main role players in the urban system relating to retail suburbanisation, i.e. the planning authority, retail firms and consumers. The dissertation discusses the results of the market research that was done among Cape Town retailers located in the CSO, and in low- and high-income suburbs. The survey collected quantitative information regarding the locational choice factors of retail managers, importance ratings of choice factors as well as stated preferences for CSO and suburban locations. The calibration results of various discrete locational choice models are discussed, including elasticities of choice factors obtained from model applications to the SP data. The development of a spreadsheet locational choice model based on typical characteristics of CSO and suburban locations is subsequently discussed. Elasticities of choice factors from the application of the spreadsheet model were determined and the model was also used to test a decentralisation trend scenario and a managed suburbanisation scenario. The dissertation makes conclusions and recommendations regarding the most important locational choice factors of retail managers, and the most effective policies and strategies for metropolitan authorities to manage suburbanisation and promote urban densification. The performance of SP models applied to spatial choices are also evaluated and recommendations are made regarding their application and further research needs.
- ItemLongbeach Mall : traffic impact assessment(Stellenbosch : University of Stellenbosch, 2001-12) Bulman, Andrew; Bester, C. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.This Traffic Impact Assessment (TIA) was commissioned in March 1998 as a supporting document to an application for the rezoning of an ert in Noordhoek from general housing to commercial use. The proposal at the time was to develop a medium·sized 15 000 m2 GLA shopping centre with supporting offices and a Health & Racquet Club. All the work (including managing the traffic counting team) was carried out by myself under the guidance of Dr Piet Jordaan at Gibb Africa Consulting Engineers. As financial backing and anchor tenants were secured for the development, the size of the proposed shopping centre was increased from a local facilily to a regional facilily of 31 000 m2 GFA to be developed in two phases. This necessitated a complete revision of the approach and content of the TIA. Owing to the regional nature of the new development, the TIA was expanded to include a wider geographical area of influence and a longer development period. This revised TIA was carried out by myself between September 1998 and March 1999 under the guidance of Dr Herman Joubert. Longbeach Mall opened for business in April 2001 complete with upgraded road network as recommended in the TIA The TIA is submitted as the final-year project for my Master's Degree in Traffic & Transportation Engineering. For the purposes of completion, an after·study of current traffic conditions on the local road infrastructure has also been included. The after·study was carried out in October 2001 (6 months after Longbeach Mall opened) and includes traffic counts at critical intersections during the Saturday morning peak period, observations of parking area utilisation, observations of shopping centre occupancy and discussions of the possible reasons for differences between predicted and actual traffic volumes. Confirmation that the study is original and was carried out by myself and permission from Arcus Gibb (Ply) Ltd to use the study as part of my final-year project, is provided in Appendix A.
- ItemMaintenance engineering standards to fulfil the legal duty of road authorities towards safe roads(Stellenbosch : Stellenbosch University, 2016-03) Roodt, Louis de Villiers; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The road network is a mode of communication that is important for the movement of people and the distribution of goods. Ownership of roads is vested in public entities. The provision of roads follows need, but is influenced by policy and funding from the public purse. The supply of roads infrastructure is therefore discretionary. The maintenance of roads is subject to operational needs, safety requirements and treasury guidelines on asset management. Maintenance of road assets, in particular safety-related maintenance, may be mandatory to meet accepted engineering standards and the expectations of communities. South Africa has a poor road safety record. Deaths per annum resulting from motor vehicle accidents peaked in 2006 at over 15 000 and stabilised at around 13 800 from 2008 to 2012. The road conditions, in particular failures, play a role in many of the accidents. Most road failures result from inadequate maintenance. The legal duty to ensure that roads are reasonably safe to use has been confirmed in legislation, policy and case law. Failure to perform this legal duty may lead to damages, for which the road authority will be liable in delict. For a case to succeed, the elements of delict must be satisfied. An act or omission that caused the damages must exist and it must be proven that the road authority was at fault. If the act was wrongful and the road authority acting through its employees is found to have acted negligently, the plaintiff’s claim will be awarded based on the contributory negligence of all parties involved in the accident, leading to apportionment of damages. Negligence is not only related to failure to maintain the road to generally accepted standards, but also in not having systems to manage, organise, execute and control the maintenance need and actions. This thesis discusses road safety, the development of standards, asset management processes and legalities. Critical characteristics of the road are identified and standards proposed. The maintenance of such standards will provide a strong defence against claims of negligence. The thesis further analyses case studies of decided claims and investigated accidents to determine principles and norms that have evolved in law. The thesis proposes a set of standards, threshold values, inspection cycles, reaction times and decision triggers to inform the maintenance of road infrastructure for safer roads. These standards include threshold values for the dimensions of potholes, edge breaks and drop-off, rutting, skid resistance, the affirmation of sight distances through the control of vegetation and location of trees. It lists trigger values for maintenance actions that must be performed to mitigate hazardous conditions, including drainage, signs and guardrails. The research forms a foundation for industry practice guidelines on maintenance for safer roads in the context of the road authorities’ legal duties towards road safety.
- ItemMorning peak period travel characteristics of a residential suburb in Cape Town during a school and holiday period : what lessons can we learn?(Stellenbosch : Stellenbosch University, 2008-03) Hermant, Laurent Fernand Leon; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: It is argued that an understanding of variability is central to the modelling of travel behaviour and the assessment of policy impacts and is not the peripheral issue that it has often been considered. There is a growing need to assess multi-day data to assess the distribution of user charges for road pricing, or patterns of public transport usage as well as improve the ability to identify mechanisms behind travel behaviour for modelling purposes. Drawing on studies worldwide, in conjunction with a review of the literature, the thesis first examines the relevance for using multi-day data, then discusses the methodology and results of a five week survey undertaken specifically for this study, makes a comparison of the findings with that observed in other studies, and finally discusses issues relating to the application of the data and future research possibilities. Previous studies have shown that behaviour which makes up the daily travel pattern can be highly repetitious in nature but that observing an individual’s behaviour on a single day might not be representative of their routine travel and that this behaviour varies across demographic segments and driver gender. This paper examines day-to-day travel behaviour variability of a residential area, Summer Greens, located in Cape Town (South Africa) using a travel dataset collected recently in November/December 2006. The survey technique employed was the recording of numberplates of all exiting vehicles from 06:00 to 10:00, weekdays from Monday to Friday over a period of five weeks. A total of 5677 vehicles undergoing 44 743 trips was observed and analysed. This research replicates and extends previous work dealing with day-to-day variability in trip-making behaviour that was conducted with data collected by Del Mistro and Behrens (2006) in Buitengracht Street, Cape Town CBD, in July/August 2005. The present research extends the earlier work by including departure time variations as well as conducting the observations during both a school period (3 weeks) and consecutive holiday period (2 weeks). Further, the thesis presents a method to measure day-to-day variability using the available data surveyed. This thesis finds a considerable difference in school and holiday traffic volumes as expected, but that despite this, certain identical travel behaviour patterns (such as vehicle appearance frequencies, following week repeat proportions etc.) is observed during both these periods. It was found that the peak hour for both school and holiday periods occurred during the same time period and greater traffic volume variability was found to occur on Fridays during the holiday period than in the school period. Traffic volumes across all weeks appeared to decrease from Monday to Wednesday and “bounce back” on Thursday and Friday consistent with the findings of another international study. It was found that motorists exhibited more departure time freedom during the holiday period with average holiday departure times much later than during the school period. Departure times were also observed to gradually become later from Monday to Friday during both the school and holiday periods with Thursday and Friday departure times significantly different to the other weekdays. The proportion of unique vehicles observed was found to increase with time of day and the resulting impact of this on the effectiveness of Variable Message Sign (VMS) applications is also discussed. The research concludes by applying the findings to determine the impact of a hypothetical congestion pricing scheme on traffic volumes.
- ItemOorsake van padongelukke met verwysing na die R44 tussen Somerset-Wes en Klapmuts(Stellenbosch : Stellenbosch University, 2004-12) Vogel, Liesel; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: South Africa, and other developing countries, experience great problems concerning road traffic accidents. Despite road safety campaigns like Arrive Alive being launched, accident rates do not decline significantly and the problem is predicted to get worse. This study is done on a road in the Western Cape, the R44, to investigate the causes of road accidents. The causes of the accidents are deduced from the accident reports and relationships are sought with other factors. The results of this study are risk factors (human-, environment- and vehicle factors) for the 14 accident types that occurred on the R44, as well as measures to prevent road accidents. It has been found that the human factor plays the biggest role in road accidents. Out of the 404 accidents analysed, 77.7% were caused by human factors, 8.7% by unknown factors, 7.2% by environmental factors and 6.4% by vehicle factors. The problems experienced with the data quality are reported and recommendations concerning it are made.
- ItemPost-calibration and quality management of weigh-in-motion traffic data(Stellenbosch : University of Stellenbosch, 2010-03) De Wet, Dirk Pieter Gerhardus; Bester, C. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Weigh-in-motion (WIM) scales are installed on various higher order South African roads to provide traffic loading information for pavement design, strategic planning and law enforcement using a scientific approach. The two most respected international guideline documents for WIM systems are the American ASTM E1318 Standard and the COST 323 European Specification, yet neither are fully suited to be applied to local WIM systems. The author developed a post-calibration method for WIM data, called the Truck Tractor (TT) Method, to correct the magnitude of recorded axle loads in retrospect. It incorporates a series of powerful data quality checks. The TT Method is robust, accurate and adequately simple to be used on a routine basis. The TT Method uses the truck tractor loads of articulated 6- and 7-axle trucks with single steering- and double driving axles – these vehicle are called Eligible Trucks. Only Eligible Trucks with average axle loads between 6.5 t and 8.5 t are used in the calibration process – these vehicles are called Selected Trucks. A calibration factor, kTT, is determined using a fully automated iterative procedure, and multiplied with all axle load measurements to produce data for which the average truck tractor load of Selected Trucks, TTT, is equal to 21.8 t. The TT Method can be used for WIMs in various operating environments and is not sensitive to the extent of miss-calibration of a WIM, clipping of sensors owing to poor lane discipline or different extents of loading on different routes. The TT Method includes a series of data quality checks that can be used on a routine basis. They are summarised as follows: - The standard deviation of truck tractor loads for Selected Trucks, STTT, should always be below 2.0 t, but preferably below 1.9 t. - The standard deviation of front axle loads for Selected Trucks, SFTT, should always be below 0.9 t, but preferably below 0.8 t. - The post-calibration factor from the TT Method, kTT, should be between 0.9 and 1.1. The factor for any month should not deviate by more than 3% from the moving average of the previous five months. - The average of front axle loads of Selected Trucks, FTT, should be between 5.6 t and 6.6 t; the exact values are influenced by load transfer between the steering and driving axles. - A procedure was formulated using the Front axle / Truck tractor Ratio, FTR, to identify the percentage of Eligible Trucks that in all probability clipped the sensor. The percentage of these records must be below 10 %, but preferably below 6 %. The TT Method has the potential to significantly improve WIM data collection in South Africa. The calibration module of the TT Method, i.e. the procedure to calculate kTT, has already been accepted by SANRAL. Most of the data quality checking concepts associated with the TT Method were also accepted, although their threshold values are still being refined.
- ItemPreparing bus and taxi operators for tendering in the Western Cape(Stellenbosch : Stellenbosch University, 2001-12) Jakoet, J. (Jamiela); Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: In an attempt to improve the efficiency of the transport system, the national government has instituted a new tender system for public transport contracts. Small bus and taxi operators are unfamiliar with operating in the formal sector. This study focuses on the extent of their disadvantage in the current tender system and recommends measures to counterbalance this. A questionnaire was devised to determine how much assistance these operators would require to prepare them for the tender, using the model bus tender document as a basis for this. The response rate was 20% with 14 taxi and 17 bus questionnaires being retrieved for analysis. The results showed that 10% of operators had no know ledge of the tender and many needed training in basic accounting and business procedures as well as public transport operation skills. Recommendations included institutional changes in public transport funding, management and allocation of resources as well as the type of education and training required. These changes should be implemented soon enough to ensure that small, medium and micro enterprises (SMME) operators are well prepared for the new tender system.
- ItemA stepwise approach towards achieving a multimodal platform within the context of the CoCT’s land transport networks(Stellenbosch : Stellenbosch University, 2013-03) Struwig, Claudia Bernadine; Bester, C. J.; Andersen, Simen Johann; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The importance of transport should not be underestimated. Transport progresses a person’s quality of life: it connects people to one another and provides access to work, services and recreational opportunities. However, post-apartheid South Africa is unfortunately still faced with a legacy of segregation. While the less-privileged, who mostly live at the fringe of Central Business Districts (CBDs), are captive users of public transport, the private vehicle trend, under the privileged, is becoming more evident. This research project thus proposes that a balanced and integrated sustainable transport system be promoted. That is, one that will aid South Africa in growing and improving its general socio-economical status by providing all its citizens with (equal) access to a balanced transport network. It is believed that, if a multimodal system is promoted, the deficiencies of the current heterogeneous non-integrated systems may be overcome. Therefore, if South Africa’s transport network is augmented with a multimodal platform, the nation will be able to move its citizens effectively and efficiently, without jeopardising the economy, social matters and the environment, today and in the future. Moreover, South Africa will also have the necessary stimulus to utilise the already available resources at its disposal by working together as ‘one’. This research project thus stipulates a (generic) sequential approach needed in achieving an integrated (sustainable) public transport system. The goal of this research project is to create awareness of the benefits that may arise from, and the implementation steps required in obtaining, such a multimodal platform. The focus area for researching the proposition made herein is the City of Cape Town’s (CoCT’s) land transport networks. The City has a management facility, with resultant transport data repository, known as the Transport Management Centre (TMC). This TMC is regarded as one of the finest state of the art facilities in the world and the features thereof offer a sufficient base and point of departure for the promotion of a multimodal transport system. By conducting research in this field, the following portraying aspects, needed for the realisation of the proposition made herein, were found. Firstly, in order to obtain an integrated sustainable transport system, the appropriate Intelligent Transport Systems (ITS) need to be integrated. It is believed that, if an intelligent transport scheme, grounded on ITS applications, is advocated, the City will be in the position to more effectively monitor what is going on, to more accurately predict what might happen in the future, and to manage its transport system proactively on an area-wide basis. Secondly, in order to meet the integration requirements imposed by multimodal transport, a centralised database needs to be created. With such a database in place, information sharing across all modes of private- and public land transport, and thus also between the investors or the operators, will be possible. An example of such a database was developed in Microsoft Access and the modes considered therein are: MyCiti, Metrorail and Golden Arrow Bus Service (GABS). The data stored in this database is historic, but the incorporation of real time information was also catered for. Thirdly, it is believed that the success of the City’s transport system, and the development of a multimodal system, is dependent on the provision of an efficient Advanced Traveller Information System (ATIS). The idea is to promote multimodal transport as a convenient transit option by providing travellers with information on journey planning that aims to counteract their reluctance to change. In order to develop such a multimodal Journey Planner (JP), the unimodal networks considered herein were combined into a supernetwork on which Dijkstra’s Shortest Path Algorithm was applied. This algorithm was programmed in Microsoft Excel’s Visual Basic for Applications (VBA) and it incorporates the following user criteria: the origin, the destination, the user’s mode preference, and the user’s optimisation preference of either time or distance. In conclusion, it can be argued that, with information becoming such a vital commodity in everyday life, the catering for informed travellers are the key to successful future transport services. If travellers are informed about the transport networks’ performance, a positive attitude is fostered. Moreover, by providing travellers with information on journey planning, their feelings of uncertainty and fear of the unknown, that are present in (especially) public transport services, may be neutralised. This information will give the public carte blanche to make decisions that give them the perception of having more ‘control over their lives’. Therefore, if a multimodal JP that can be accessed from one portal is created, people’s inclination to acquire more information will be met. And as a result, traversing in an integrated manner may become the norm.
- ItemTowards a non-intrusive traffic surveillance system using digital image processing(Stellenbosch : Stellenbosch University, 2001-12) Lorio, Berino; Herbst, B. M.; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: With the increased focus on the use of innovative and state-of-the-art technology in Intelligent Transport Systems (ITS), the need for more accurate and more detailed road traffic flow data has become apparent. Data obtained from vehicle detector loops, which merely act as vehicle presence sensors, is neither reliable nor accurate enough anymore. This type of sensor poses the problem that it has to be inserted into the road surface; temporarily obstructing traffic flows, and has to be replaced after pavement reconstruction. One of the solutions to this problem is to develop a traffic surveillance system that uses video image processing. In cities where Intelligent Transport Systems are used extensively, roadways are monitored through Closed Circuit Television Cameras (CCTV) that are closely watched by traffic control centre personnel. These cameras are mounted on posts on the roadside. These cameras can serve a dual purpose, being used for both human monitoring and as inputs to Video Image Processing Systems. In this study some of the digital image processing techniques that could be used in a traffic surveillance system were investigated. This report leads the reader through the various steps in the processing of a scene by a traffic surveillance system based on feature tracking, and discusses the pitfalls and problems that are experienced. The tracker was tested using three image sequences and the results are presented in the final chapter of this report.
- ItemTowards the extension of the knowledgebase to further the understanding and modelling of driver behaviour(Stellenbosch : Stellenbosch University, 2003-04) Poolman, Pieter; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The problem of how the mind relates to the brain stands as one of the greatest challenges today. The materialistic worldview and pragmatic approach to social problems are both being transformed by discoveries of how human experience and culture arise in cerebral activity. Even so, this effort, spearheaded by neuroscience, has seen the important and contentious issue of driver behaviour somehow been left behind. From an extensive literature study, it can be concluded that gross disregard of the neural underpinnings of such behaviour tied to a behaviouristic approach is endemic to the field. Numerous qualitative psychological models (each associated with debates about their validity) and Artificial Intelligence models, which effectively only imitate robots 'impaired' to display some humanlike characteristics, were come across. Although neural networks are derived from current knowledge of computation within the brain and deployed in industry, human driver behaviour modelling is not benefiting from this revolution in humanlike information processing. To date, very little has been done to determine what makes road users speed, drive while drunk, overtake, or yield at crossroads. As the central nervous system is the human measuring device in and of the world and thus key affector of human behaviour, it is ofutrnost importance to invest resources in 'inoculating' the field of driver behaviour modelling onto a robust basis provided by neuroscience. Being a human driver incorporates a broad complement of interrelated brain systems to perform driving tasks (psychological functions) at hand, such as lane keeping, speed choice, risk perception, and obstacle avoidance. The proper level of analysis of such a psychological function is the level at which that function is represented in the brain. Providing a theoretical model of human behaviour, based on biological facts of the brain as a whole, is surely a challenge for decades to come, but the field of driver behaviour should be part of such an effort. Collaboration is needed among investigators from the fields of neuroscience, psychology, mathematics, computer science, and engineering to further driver behaviour modelling. It is uncommon that professionals from these fields have a thorough understanding of the other fields involved, but the author, not pretending to be an expert, argues that such a union of fields will be of significant value not only to transportation, but all behavioural sciences. The wealth of to-date knowledge amassed in neuroscience lies ready to be tapped by researchers interested in explaining human driver behaviour. To this end, the use of modem brain-imaging techniques will be invaluable in pinning down the neural correlates of particular driving subtasks, bearing in mind the extent of structural impacts on the brain of each individual, brought about by a lifetime of interaction with the environment. Thus, based on the findings of this literature study, the author proposes that supplementary work be conducted by a multi-disciplinary team to roll-out an experiment to study the nature of environmental stimuli as instigators of aggression and road rage, by drawing on knowledge about brain imaging and (amygdala) activation.
- ItemVideo data collection method for pedestrian movement variables & development of a pedestrian spatial parameters simulation model for railway station environments(Stellenbosch : Stellenbosch University, 2012-03-14) Hermant, Laurent Fernand Leon; Bester, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The design of railway station environments in South Africa and to a certain extent internationally, is based on rules of thumb. These rules, using general macroscopic principles for determining peak passenger loads are inadequate and misleading for detailed design purposes. The principles advocated in local design guideline documents are erroneous and ignore the highly variable flow nature or “micro-peaking” effects that typically occur within railway station environments. Furthermore, there are no procedures proposed in these guideline documents, which leads to ambiguous assessment techniques used by practitioners in the determination of pedestrian spatial areas. It is evident that the knowledge in the area of pedestrian movement contained within the design guidance is far from comprehensive. Without a reliable method for estimating pedestrian levels-of-service and capacities, design of new facilities does not follow a uniform process, resulting in high levels of uncertainty in determining if the time, money and resources invested in upgrading facilities will actually cater to the demand. The situation is further exacerbated by current industry thinking towards pedestrian modelling in South Africa, where it is perceived by both clients and practitioners to be more cost effective to use macroscopic techniques and designing infrastructure according to a “one-level-up” level-of-service method. Working with architects confirmed that the area of circulation design was lacking in data and guidance and that associated quantified assessments of pedestrian movement was rarely, if ever, carried out. Towards addressing these issues, the development of a Spatial Parameter (SP)-model spreadsheet application became the main objective of the study. The model contributes towards addressing the needs of individual station users based on the trade-off between level-of-service and infrastructure costs. The output of the model allows the designer to avoid the under-provision (detrimental to operations) and oversizing of railway station infrastructure (with obvious financial implications). The author recognised the lack of pedestrian movement data in South Africa and addressed this by conducting extensive video-based pedestrian observations aimed at exploring the macroscopic fundamental relationships and the ways in which these relationships might be influenced by the various personal, situational and environmental factors that characterise the context in which pedestrians move. The movement trajectories of 24,410 pedestrians were investigated over three infrastructure environments at Maitland and Bonteheuwel stations in Cape Town, carefully selected to incorporate the cultural diversity common in South Africa. Tracking of pedestrians was achieved via the use of an in-house developed “video annotator” software tool. Boarding and alighting rates of 7,426 passengers were also observed at these stations incorporating contributory attributes such as age, gender, body size, encumbrance, group size, time of day, and location. The research makes a number of significant advances in the understanding of pedestrian flow behaviour within railway station environments and provides recommendations to industry of what issues to consider. The empirical study has provided comprehensive pedestrian movement characteristics incorporating the relationships between density, speed and flow including the effect of culture and other context factors unique to the local South African environment. New methods for determining spatial requirements are proposed, together with new and unique empirical data for use by the local industry. A calibrated spreadsheet SP-model for assessing the design of concourse type railway stations is developed and presented in the study. The advance in local pedestrian flow knowledge, together with the SP-model, is shown to be practical through application to two real railway station case study projects. The results of this study constitute an important contribution to local pedestrian flow knowledge and is considered a valuable resource for those developing pedestrian models in practice. It is expected that the results will be useful in the planning and design of pedestrian environments in South African railway stations and can be applied to other African metro railway stations with similar pedestrian characteristics. Overall, this research has succeeded in advancing the approach to railway station design, empirical data, knowledge and methods held within the local engineering industry. However, the contribution of this study and associated conference papers is an early step in changing the perceptions in this country towards ensuring fully informed and appropriate performance-based spatial designs.