Browsing by Author "De Silva, PCP"

Now showing 1 - 12 of 12

item: Conference-Abstract
Automatic road extraction form high resolution satellite images
(Department of Civil Engineering, University of Moratuwa., 2013-07) Bandara, RMPNS; De Silva, PCP; Bandara, JMSJ; Pasindu, HR
The presence of high resolution satellite images and their potentials to be used in many fields such as urban planning, transportation engineering etc ,especially in the meaning of preparing and updating maps, have made the automatic extraction of objects, a new challenge in remote sensing. Automatic road extraction, one of major uses of preparing and updating maps, provides means for creating, maintaining, and updating transportation network, which subsequently offers databases for all means of traffic management. Moreover, automatic road extraction is a critical feature for an efficient use of remote sensing imagery in most contexts, which has been an active research area in computer vision and digital photogrammetric for over past decades. Further, the pixel-oriented analysis of satellite data has a main limit: the acknowledgement of semantic low level information, as the amount of energy emitted from the pixel, where the context does not assume any role. Conversely, the application of object-oriented image analysis on very high resolution data allows obtaining, by an automatic or semi-automatic analysis – with a minimal manual participation – a good classification also in presence of high and very high resolution data of small cities, where higher is an error possibility. Object-oriented image classification involves identification of image objects, or segments, that are spatially contiguous pixels of similar texture, color, and tone. A simplified methodology using the object oriented image analysis for automatic road extraction for the Colombo City Area is presented in this paper. The proposed object-oriented image classification method comprises few fundamental and important steps towards content analysis and image understanding for instant image segmentation and classification. Few algorithms and techniques for the segmentation and classification in order to identify road features from satellite images were also supported to the proposed method.
item: Thesis-Full-text
Development of a GIS based transport demand estimation model that integrates land use and transportation infrastructure development scenarios
De Silva, PCP; Bandara, JMSJ
Transportation issues are becoming severe day by day in Sri Lanka. Ignoring the importance of integrating transport and land use properly in the travel demand estimation process, due to its vast complexity and not having a proper mechanism to understand it easily, is the main reason for those issues. Identifying that, this research developed a GIS based transport and land use model that helps relevant authorities to easily understand and incorporate the complex interaction to the travel demand estimation process, as the first attempt in Sri Lanka until now. The model has two sub models called macro and micro models that separately look after the regional level and local level travel demand estimations respectively, although final results at any level combine both models’ outputs. The macro model has been developed for whole Sri Lanka taking the Divisional Secretariat (DS) divisions as Traffic Analyzing Zones (TAZs). Algorithms calibrated by the linear regression analyzing technique incorporating the Origin-Destination (OD) matrix data and socio-economic data are the main modeling technique for the macro model. Optimum counting locations derived through a new approach named as the “top-down approach” for OD surveys enhanced the accuracy of the OD matrix and thereby increasing the accuracy at all stages. As a prototype, a micro model was built for the Colombo DS division. The study area of the micro model can be any geographic area according to data and time availability. The activity based approach in the microsimulation modeling technique was used to develop the micro model, which uses household and railway passenger OD surveys, for calibration. Finally, a GIS based computer program was developed to improve the effectiveness and user-friendliness of these models.
item: Conference-Full-text
Estimate the pass-by and diverted trip impact generated by a supermarket in Colombo, Sri Lanka
(Faculty of Architecture Research Unit, 2022-12-02) Pathiraja, ALAC; De Silva, PCP; Jayasinghe, AB
A new supermarket development will produce more trips, adding to the existing traffic and eventually leading to congestion and increasing clashes on nearby roads. One of the primary lands uses in the Colombo area is the supermarket. As a result, it will affect travel demand as well as other local transportation-related concerns. To accurately assess the level of congestion and the effects of the development on the network, it is essential to estimate the actual number of trips that a new supermarket will generate. All land use trips do not just trip to that destination and return (primary trips). Some of the generated trips (pass-by trips) are already in the existing traffic, but some of the generated trips are entirely new (diverted trips). These trips should be analyzed while planning development to determine the impact on the surrounding transport network. Therefore, this research objects to calculate the proportion of primary, pass-by, and diverted trips generated by a Supermarket in Colombo, Sri Lanka. Current vehicle trips attraction/generation of the supermarket, consumer trip chain pattern and vehicle volume of the access road are the primary research input. Five supermarkets in the Colombo area were selected as case studies, and descriptive analysis using SPSS software and Microsoft Excel was used for analysis. Results indicate that on average 43.7% of Pass-by and diverted trips will be generated by a new supermarket in the Colombo area. This paper leads to calculating the real traffic impact by a Supermarket on surrounding road network based on the pass-by and diverted trips in Colombo, Sri Lanka.
item: Conference-Abstract
Estimating the catchment area of a supermarket in Sri Lanka
(Sri Lanka Society of Transport and Logistics, 2020-11) Pathiraja, ALAC; De Silva, PCP; Jayasinghe, AB; Gunaruwan, TL
Unplanned developments are a serious issue contributing to traffic congestion in most countries. Therefore, a "Traffic Impact Assessment (TIA)" for with a proposed development should be undertaken before granting approval to proceed. Locally, the Urban Development Authority (UDA) in Sri Lanka considers a 500m radius from the site boundaries as the traffic impact study area in which TIAs are conducted. Many scholars argue that the geographical extent of a traffic impact area is not fixed: it may differ and should therefore be flexible. The vehicles attracted by new retail developments negatively impact on transport, contributing to traffic congestion relative to other developments. Retail stores along the road network generate additional traffic and change the spatial travel pattern of the street network. Therefore, it is better to understand spatial configurations and classify the retail spatial patterns of retail stores. This paper derives the spatial patterns of retail activity in Colombo, Sri Lanka by calculating the level of street integration and street connectivity using the space syntax technique in depth map software. This paper categorizes spatial patterns of retail activity to delineate the true catchment area of a supermarket through the GIS overlay tool and Network-Based Kernel Density Estimation (NKDE). The findings of this research illustrate that the true catchment area is not fixed and will differ based on the diverse operational requirements of each new retail development. This helps to create a better understanding of spatial patterns of the urban retail stores in Colombo area. It supports strategies for sustainable planning and development.
item: Conference-Full-text
Evaluate the onsite three-wheeler parking requirement of supermarket developments to mitigate the parking-related traffic impact in Colombo, Sri Lanka
(Faculty of Architecture Research Unit, 2023-12) Pathiraja, ALAC; De Silva, PCP
Parking plays a fundamental role in any transportation system, serving as a crucial element in mitigating traffic congestion and enhancing the overall mobility experience. In Sri Lanka, particularly in commercial and shopping areas within the City of Colombo, the issue of roadside parking has emerged as a significant challenge. This predicament has been exacerbated by the spread of private vehicles, especially three-wheelers, which often operate without dedicated parking spaces despite existing regulations in Sri Lanka. This research endeavours to bridge the divide between the legal requirements, as stipulated by regulations, and the actual operational demand for three-wheeler parking in supermarket areas within Colombo, Sri Lanka. By conducting a meticulous comparative analysis and employing statistical tools like SPSS, the study seeks to provide valuable insights into the onsite three-wheeler parking needs of supermarket developments. The ultimate objective of this research is to establish a standardized framework for allocating three-wheeler parking slots within supermarket areas. This framework aims not only to cater to the existing parking demand but also to alleviate the parking-related traffic issues that currently plague Colombo's commercial and shopping areas. In doing so, this research aspires to contribute to the optimization of urban transportation, making it more efficient and accessible for all road users while also fostering sustainable urban development in the vibrant city of Colombo, Sri Lanka.
item: Conference-Abstract
A GIS based tool to estimate transport demand associated with land use changes expected at an expressway interchange township development
(Department of Civil Engineering, University of Moratuwa., 2013-07) De Silva, PCP; Aseem, M; Bandara, JMSJ; Pasindu, HR
The first ever expressway in Sri Lanka has already been declared open at the end of 2012 and authorities are planning for township developments at three of the expressway interchanges closer to the City of Colombo. A number of different land use and transport infrastructure proposals have been put forward but there is no tool to evaluate the effectiveness of transportation infrastructure proposals or to identify the traffic impacts due to land use developments. Models available for intercity travel demand cannot be used for this macro and micro level planning and not having sufficient traffic and travel related information is another serious issue faced by the planners. The objective of this paper is to present a tool developed based on GIS to facilitate the travel demand estimation within the township development area. This tool make use of the outputs of an intercity demand model (TransPlan) and distribute the trip ends within the study area using land use and local area transport network using GIS tools. This tool is based on Arc GIS software and Visual Basic has been used for different tool developments. Demographic information available on smallest level administrative divisions (Grama Niladhari Divisions) and traffic counts carried out at strategic locations are used for the traffic flow distributions. GIS tools developed to find out link and node independent paths, trip generations and trip attractions based on land use information are used to evaluate different alternatives. This tool is transferable to any geographic area and can be customize depending on the level of data availability. A case study representing one of the townships (Kottawa, at the end of Sothern Expressway) is presented to demonstrate the application of this tool.
item: Conference-Abstract
Methodology to identify the optimum number of locations that minimized double counting errors for origin – destination surveys
(Department of Civil Engineering, University of Moratuwa., 2013-07) De Silva, PCP; Bandara, JMSJ; Pasindu, HR
An origin – destination matrix is a spatially disaggregated measure of the traffic demand within a defined study area. Further, results of origin – destination (OD) surveys, which primarily comprise information about the spatial and temporal distribution of activities between different traffic zones, are of vital importance for transportation systems operation, design, analysis, and planning. However, in the OD estimation process, the quality of the estimated OD data is highly dependent on accuracy of the input data, which is a subsequent factor of the selection of perfect number and locations of observation. Further, although scholars argue the importance of selecting the correct sample sizes at each location in order to produce accurate data while minimizing the cost and disturbance to the traffic and etc, still it seems this factor has not been incorporated for the studies. This paper presents a new approach for establishing permanent locations for OD surveys, which enclose entire study area travel movements, by having taken divisional secretariat divisions as the traffic analyzing zones. The main argument considered here is the selection of minimum number and keeping no room for the double counting. Further, the paper evaluates sample sizes required for each counting location for OD surveys.
item: Conference-Abstract
Modeling transport and land use in micro-level (a case study of Colombo DS Division, Sri Lanka)
(Department of Civil Engineering, University of Moratuwa., 2015-08) De Silva, PCP; Madushani, KHA; Bandara, JMSJ; Pasindu, HR
In transport planning, two major approaches can be seen: namely, micro-level (local, intracity) and macro-level (regional, inter-city) planning. The different nature of the micro-level and macro-level travel behavior is well acknowledged in the literature. Therefore, to make informed transportation planning decisions on micro level, planners and engineers have to be able to predict travel characteristics and usage of transport services under different socioeconomic scenarios, transport services and land use configurations comparing macro-level travel demand estimations (Litman, 2008). Therefore, separate transport and land models also need to be prepared to micro-levels as well. In micro-modeling aspect, absorbing the minor level data is a difficult task. The task becomes harder in areas where a complex interaction of transport and land use is visible. Further, micro models needs to incorporate the macro-models’ outputs to a certain extent. Therefore, the modeling process, which comprises the collection of data, preparation of maps and databases, development of algorithms becomes more multifaceted. This paper explains the modeling process involved in an attempt made for the development of micro-level transport and land use model for the Colombo DS Division. The Colombo DS Division has the most complex interaction between transport and land use in the western region as well as in the whole country and further, this model has been developed using the activity based modeling process in the micro-simulation approach. Here, household interview travel surveys, railway passenger origin-destination surveys and GIS analysis were primary used for supporting the modeling process. Moreover, matters and questions encountered while developing the model were also included in the paper.
item: Article-Full-text
Requirement Area Review: Flexible Study srea For Traffic Impact Assessments
(Faculty of Architecture University of Moratuwa, 2020-11) Pathiraja, ALAC; De Silva, PCP; Jayasinghe, AB
New developments will contribute to increased traffic to the external environment. Therefore, the majority of nations, in planning and building regulations and guidelines have adopted steps to control them beforehand. Similarly, in Sri Lanka, new developments in the approval process should be undertaken, based on their legal specifications and through a Traffic Impact Assessment (TIA). Although the management of traffic from new developments is exceedingly positive, one of the problematic sectors noted in the TIA study is a fixed study area. Consequently, a 500 m buffer area from the proposed site edges is currently being taken as the study area in Sri Lanka. The geographical extent of the traffic impact area is not a fixed bound-ary. Particularly based on a set of parameters, the true catchment area could be changed. A fixed boundary may, therefore, misdirect developers, consultants and planning authorities in decision making in situations of transport planning. Owing to this very debatable selection, almost all studies have been incorrect. Consequently, this research focuses on investigating the requirement of flexible study areas for traffic impact assessments of distinctly unique developments
item: Conference-Full-text
Review of suitable parameters and methodologies to delineate the traffic impact area from a proposed development in Sri Lankan context
(2019) Pathiraja, ALAC; De Silva, PCP; Jayasinghe, AB; Samarawickrama, S
An upcoming development usually generates both vehicles in and out to the accessible and adjacent roads and junctions. Therefore, most countries have adopted different planning and building regulations and guidelines to manage them in advance. Although, there is a vast positive movement in guidelines in Sri Lanka as well, still doubtful areas could be observed in delineating the traffic impact area properly. A 500m buffer area from the proposed site is currently taken as the minimum study area at developing the traffic impact assessments which is mentioned under the Term of Reference (TOR) in Sri Lanka. The geographical extent of the traffic impact area is not a fixed boundary, which could be changed especially based on varieties of parameters. Therefore, a fixed boundary may misdirect the developers, consultants and planning authorities at the decision making in transport planning circumstances. Thus, many studies have gone wrong due this very subjective selection. Therefore, many scholars in the transportation field and its allied disciplines argue the importance of developing suitable parameters and methods to delineate the traffic impact area for each development uniquely. Only a few number of models, techniques, and algorithms would be observed on this subject from present assessments. Hence, the objective of this research is to review relevant methods and parameters from past studies and to select the most suitable parameters and methods for delineating the traffic impact areas for proposed developments in the Sri Lankan context. Most suitable parameters and methodologies were identified through the Snowballing technique and multi-criteria analysis for delineating the extent of the traffic impact area from a new development
item: Conference-Abstract
The usage of remote sensing and other geospatial methodologies to assess and manage road infrastructure
(Department of Civil Engineering, University of Moratuwa., 2016-08) De Silva, CS; De Silva, PCP; Bandara, JMSJ; Pasindu, HR
One of the most valuable and extensive infrastructure resources in the country is its road network and therefore, its assessment and monitoring is crucial to ensure that a safe and effective road system is in place. However, the process of evaluating the condition of transportation infrastructure, especially roads is an expensive, time consuming, and a highly labour intensive one. Most of the road evaluation methods widely used today use measurements that are taken in situ along with visual examinations and interpretations. However, the measurement and assessment of damage and deterioration of roads is in most instances qualitative and is limited to point observations. This is where remote sensing technologies come in to play. Remote sensing offers non-destructive methods to assess and monitor road conditions with very large spatial coverage without even having to leave the desk. Hence, the objective of this study is to bridge traditional road evaluation procedures with new technologies to overcome the cost and time constraints currently associated with it. This study introduces an automated set of tools that will allow the user to remotely capture important features related to the road infrastructure on the basis of satellite images pertaining to the area that will enable an effective assessment and monitoring process of the roads. The set of tools will be hosted by ArcGIS Model Builder and the significance here is that since the entire tool is automated, regardless of the user‟s knowledge in ArcGIS, they will still be able to make use of it. Because remote sensing is capable of collecting information from a wide spatial spectrum in a very short period of time, this set of tools will be invaluable in assessing and managing road infrastructure in the country, although it is important to acknowledge that these methodologies can never fully replace traditional geotechnical methods.
item: Conference-Abstract
Waterway transportation – an alternative mode for reducing the urban traffic congestion (a case study of Colombo City area)
(Department of Civil Engineering, University of Moratuwa., 2016-08) Senavirathne, SWMP; De Silva, PCP; Bandara, JMSJ; Pasindu, HR
The waterway transportation specifically as an inland transportation system has been providing many solutions for improving the functioning of urban logistics. (Taniguchi, Nemoto 2008) The following study was carried out to identify the feasibility of establishing a waterway passenger transportation system based on the Beira Lake and the canal system in the Colombo Municipal Council area (CMC). The CMC and the Western Province undergoes a huge development project which is Western Region Megapolis Master Plan which expects an increment up to 4.4 million passenger trips by 2035 which is 1.9 million in the present situation. (WRMMP, 2016) These rates would certainly increase the traffic congestion in the CMC area and would cause for more economical loss which is 32 billion rupees annually in the present due to the increased traffic congestion. The study focuses on establishing an alternative transportation system to avoid the traffic congestion in the CMC area. Initially, using the GIS Thiessen polygon tool the study area was sub divided into zones based on the nodes of the road network. A Trip Generation – Attraction model was used to calculate the number of trips transferred through the zones based on the respective population and employments. Using the Gravity Model the number of trips were distributed among the zones considering the centroid as the trip origin and destine point. Secondly, it was identified that the trips included in the roads where the carrying capacity has been exceeded can be transferred through the waterway transportation system. The study findings can be concluded that the Beira Lake and surrounding of 1 km buffer zone generates approximately 4 million trips of the length of 3.5 km which can be considered as prospective trips for the waterway transportation system. The study showed that the waterway transportation system is a well adoptable alternative mode to ease the traffic congestion in the CMC area.