Browsing by Author "Rajapaksha, RPGKS"

Now showing 1 - 7 of 7

item: Conference-Abstract
Accommodating road accident records in a comprehensive highway management system
(Department of Civil Engineering, 2011-07) Bandara, JMSJ; Silva, SA; Rajapaksha, RPGKS; Pasindu, HR
It has become important to improve planning, design, construction, operation and maintenance standards and manage road system efficiently. There are number of management systems such as pavement management system, road inventory systems, accident data recording system, traffic and passenger demand models, traffic assignment models have been established to handle different stages of road transport. As different organizations are responsible for the above different processes it is imperative to have these systems coordinated to have an integrated highway management system that will share information, expectations and experience. Today road accidents have become a significant negative impact to all road users. To reduce the number of accidents, it is important that manage the accident data in systematic manner because it will provides lot of information. This data is very important to traffic and highway engineers because it helps them to identify the unsafe location of the roads and the reasons for that. This is essential in road improvement projects to carry out safety audits and find the solution to minimize the number of accidents. This paper presents how a road inventory and accident data system could be integrated to share information from one another. In addition the paper highlight how road inventory data and accident data can be used to analyze accidents at road link, road type or administrative area vise and identify accident prone locations or reasons for different types of accidents. The programme was written using VBA (Visual Basic for Applications) which is more relevant to customize ArcGIS Desktop Applications to store the data in a Microsoft access database and filter the database using the developed VBA interface. For example, users can find out the number of accidents on a location according to various crash factors contributing to the accident from human side, vehicle side and road environment side. According to filtering combinations, model is developed to show the number of persons died, injured and detail list of accidents. The model has capability to connect road inventory data and accident data with attribute tables in ArcGIS. Therefore, engineers can directly use the GIS tools to represent and analyze the above data in an efficient manner.
item: Conference-Abstract
An approach to evaluate horizontal alignment of highways using curvature index and operating vehicle speed
(Department of Civil Engineering, University of Moratuwa., 2011-07) Rajapaksha, RPGKS; Bandara, JMSJ; Pasindu, HR
In recent years, Sri Lanka has experienced an urban traffic congestion that caused a waste of time and energy. It is known that road geometries partly contribute towards decrease in operating vehicle speed. According to conventional Highway Geometric design procedure there is no accurate method to predict operating vehicle speed with different combinations of horizontal alignment (variation of bends with respect to different curvatures). This study explores a methodology to evaluate the actual horizontal alignment of roads to increase the efficiency of highway management with respect to reducing travel time. In this paper after classification of all the design elements, the new concept of “curvature Index” (the degree of angle variation per unit length) is introduced to represent actual horizontal alignment of a road segment including number of bends and nature of bends. The curvature index measures analyzed were : bend density (number of bends per km); cumulative angle (degrees per km); mean angle (degrees); and standard deviation of angles. The research confirmed that driver's speed choices are more strongly related to curvature Index than curve design speed, and to the approach speed environment. The curvature index and operating vehicle speed is estimated using the database of GPS (Global Positioning System) receivers. GPS data is collected at selected road segments in Sri Lanka closely representing free flow condition. A methodology is developed to increase the reliability of GPS data obtained in order to investigate the relationship between curvature indexes and operating vehicle speed. Simple linear regression analysis is used to develop operating vehicle speed models, which related driver speed to the curvature Index of the highway. ArcGIS (Geographical Information System) provides a good platform to model relationship between curvature index and operating vehicle speed because the analysis tools in GIS can be directly used to analyze the GPS data.
item: Conference-Abstract
Effect of traffic composition on capacity of two-way two-lane, roads under mix traffic condition
(Department of Civil Engineering, 2017) Rajapaksha, RPGKS; Bandara, JMSJ; Pasindu, HR
Traffic performance of a road section is expressed in terms of Level of Service (LOS). The Highway Capacity Manual (HCM) developed by the Transportation Research Board of the National Academies of Science in the United States provides procedures to determine LOS based on analysis of capacity of a road. It divides the quality of flow into six levels ranging from level A to F. These definitions of quality are based on measures of effectiveness of the road which include speed, travel-time, density and delay. Road development authorities in Sri Lanka are adopting the methodologies given in the HCM due to the lack of guidelines specific for the country. However, the HCM methodologies may not depict the correct traffic performance of roads owing to the nature of the mix of vehicle types in the traffic stream, the lack of lane discipline and irregular road side activities. This may lead to incorrect decisions in planning, designing, maintenance, rehabilitation, and operation of roads. Therefore, it is necessary to study traffic performance in Sri Lanka, and to evaluate the transferability of methods used in other similar countries in order to develop appropriate and applicable approach to mix traffic Condition. Subsequently, in order to evaluate traffic performance, it is important to study about operational characteristics of traffic stream. In a pilot study under this work, capacity of a road was found to be affected by the traffic composition and control condition. Therefore, characteristics of vehicle composition in different capacities have been considered and study was focused to two waytwo lane roads. Different size, power, and maneuverability performance of vehicles cause significant level of friction to the movement of other vehicles in a mix traffic stream. For an example, in a high traffic volume stream, a large proportion of motorized two wheelers and three wheelers are able to move with speeds closer to their free speeds due to the ability of utilizing smaller gaps in the traffic stream, while the large-size vehicles are subjected to significant speed reduction. Characteristics of fundamental traffic flow parameters (Speed, Density and Flow) in traffic streams with different compositions of vehicles were studied. One-Sample Kolmogorov Smirnov test was performed to check normality of speed of collected data samples under prevailing conditions and it has shown that speed distribution is significantly deviate from normality (P-value < 0.05) under different compositions and traffic volumes. It is observed that speed distribution shows bi-modal distribution in roads which wheelers and three wheelers. One-way analysis of variance (One-way ANOVA) tests was carried for speed characteristics of group of two wheelers, three wheelers and four wheelers. Null hypothesis (Ho) that there will be no significant difference between different groups of vehicle speed sample means was rejected with 95% confidence level (P-value < 0.05). Therefore, vehicle composition has described as separate groups of two wheelers, three wheels and four wheelers. Modified continuity equation for heterogeneous driver population was used to calculate densities of traffic streams. Different traffic flow models which used to model two-lane traffic flow behavior had been tested under prevailing conditions. Greenshield traffic flow model has showed strong correction between flow and speed and it was chosen to develop speed-flow models. Finally, empirical speed - density and speed - flow curves were developed for different compositions of vehicles in order to evaluate the capacity variations under mix traffic condition.
item: Conference-Abstract
Evaluation of accuracy of the infra-red traffic logger under mix traffic condition
Rajapaksha, RPGKS; Bandara, JMSJ
Traffic data collection under heterogeneous traffic conditions is one of the major challenges faced by highway agencies, policy makers as well as researchers. The Infrared Traffic Logger is a highly advanced, non-intrusive traffic surveillance system which can detect different classes of vehicles based on wheel base size and axle spacing. The fundamental macroscopic traffic parameters: flow, speed and composition under different traffic conditions and weather condition were checked against to base line condition. It was found that overall accuracy of vehicle counts from infrared traffic logger is more than 90% except for two-wheelers under heavy traffic condition and for heavy vehicles under medium and heavy traffic condition. Speed detection accuracy of infrared traffic logger also more than 90% and accuracy of vehicle classification also more than 95% except multi axle vehicles. Multi axle vehicles are misclassify as number of twoaxle vehicles under medium or high traffic conditions. Correction factors are suggested to adjust the accuracy level for over counting and under counting situations.
item: Conference-Extended-Abstract
Finite element modelling of short span soil-steel bridge structures used in Southern highway in Sri Lanka
(2010) Induprabha, SAD; Rajapaksha, RPGKS; Siriwardana, KDYE; Jayasinghe, MTR; Lewangamage, CS
The corrugated soil Steel Structures, consisting of a combination of shells of corrugated steel plates and surrounded with well compacted backfill soil have been used in Sri Lanka for the first time in Southern Transportation Development Project as underpasses and drainage structures. This has been selected for the lower cost and the lesser construction time. In this study the effect of height of soil cover over the structure, on the stress in the steel shell of Metal Arch Underpass (MAUP) structures is analyzed to determine an optimum range for soil cover and to evaluate the structural safety of the prevailing structures. The commercially available Finite Element Software ANSYS, SAP 200 and PLAXIS 1.5 are used in modelling the structures.
item: Thesis-Abstract
Modelling the relationship between vehicle operating speed and the geometry of the roads using geographic information systems (GIS)
(2015-09-17) Rajapaksha, RPGKS; Bandara, JMSJ
It is known that road geometric features significantly contributes to the variation in vehicle speed. According to conventional Highway Geometric design procedure there is no accurate method to predict actual vehicle speed with different combinations of geometric elements such as horizontal alignment and vertical alignment etc. This study explores a methodology to evaluate actual vehicle speed variation mainly considering geometry. In this paper after classification of all the design elements, a new predictor called “curvature Index” (the degree of angle variation per unit length) is introduced to represent actual horizontal alignment variation of a road segment including number of bends and nature of bends. The curvature index measures analyzed were: bend density (number of bends per km); cumulative angle (degrees per km); mean angle (degrees); and standard deviation of angles. The research confirmed that driver’s speed choices are more strongly related to curvature Index than curve design speed, and to the approach speed environment. Similar measures were carried out for vertical alignment variation and new predictor called “Elevation Index” is introduced to represent different combination of vertical alignments. International Roughness Index (IRI) and Road width selected as other predictors to obtain the correlation between Geometry and speed. The curvature index, elevation index and actual vehicle speed are estimated using the database of GPS (Global Positioning System) receivers. Data was collected at selected road segments in Sri Lanka under less traffic condition. A methodology developed to increase the reliability and accuracy of GPS data. Simple linear regression analysis is carried out using SPSS and MINI Tab software to develop actual vehicle speed model together with ArcGIS. ArcGIS (Geographical Information System) provides a good platform to graphical analysis of data and integrate with GPS data. This study conforms positive correlation between actual speed and combination of Geometric elements. This model could be combined with other social environmental factors (e.g.: land use) and effectively use as speed prediction model or as a design tool.
item: Conference-Abstract
Strategy to identify optimum travel routes for improvements in an urban area
(Department of Civil Engineering, University of Moratuwa., 2012-07) Rajapaksha, RPGKS; Perera, L; Bandara, JMSJ; Pasindu, HR
Transportation is a basic requirement in any city in the world for its economic, social and other developments. Different cities in the world use various means of transportation to achieve their goals and objectives. In general, minimum travel time, comfort and safety can be considered as primary objectives of any cities transport plan. In urban cities, it’s a well-known fact that transport planning is imperative to achieve its day to day and long term goals. Congestion is very commonly seen condition in most of the urban areas in the world and there is no exception for Sri Lanka as well. In an urban context, users may have various origins and destinations in their travel needs varying over the time. These needs may have primarily arisen due to the land use mix or social desires. However, it is transport planners duty to full fill these transportation needs of users effectively under given circumstances. In that aspect identification of high demanding origins and destinations are very important and recognizing minimum distance or minimum travel time routes are critical. Proper information or planning system would direct users effectively and could able to cut off unnecessary congestion significantly. Thus, this study will explain a strategy to identify travel routes in urban area with respect to time and distance variables, where improvements can be done to reduce congestion effectively. Identification of prominent OD pairs, traffic flow conditions and capacities at different corridors, travel distances between OD’s, travel time between OD’s and most preferred routes by users can be considered as main inputs in this nature of study. Colombo city was selected as a case study and Origin-Destination (OD) surveys were carried out at number of selected locations along with traffic flow counts, taken at main and sub corridors connecting to Colombo city. Based on the OD survey analysis, prominent origins and destinations were recognized and travel time between each and every combination of origin and destination were measured multiple times, in peak and off peak conditions. Based on the collected data minimum travel time between OD’s and minimum travel time route were identified. Using the Arc GIS software, a road network plan was developed and minimum distance routes were identified between OD’s. Further, there are instances where users use completely or slightly different routes to reach their destinations other than mentioned above and thus those routes were also recognized as commonly used routes to see what deviates from the minimum distance or minimum time path. Comparison of three different routes obtained from the study revealed many problems and counter measures were given to improve the efficiency of existing conditions cost effectively.