Institutional-Repository, University of Moratuwa
Welcome to the University of Moratuwa Digital Repository, which houses postgraduate theses and dissertations, research articles presented at conferences by faculties and departments, university-published journal articles and research publications authored by academic staff. This online repository stores, preserves and distributes the University's scholarly work. This service allows University members to share their research with a larger audience.
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Recent Submissions
item: Thesis-Abstract
Use of CIRCLY (Austroads mechanistic design software) for overlay designs in Sri Lanka
(2025) Manjula, NWAD; Mampearachchi, WK
Road pavement design has been carried out complying with empirical methods which are not based on stress strain relationships. But the mechanistic methods which are based on stress strain relationships is the method that is complying with engineering fundamentals. CIRCLY is a pavement design software based on mechanistic approach and calculate damage factors after the design period for a given traffic load distribution. The Austroads flexible pavement design method uses CIRCLY to calculate load-induced strains and deflections in model pavements. CIRCLY is an integral component of the AUSTROADS Australian Pavement Design Guide. Considering about the data required to carry out the design of road pavement it was recognized that Flexural Modulus, Poisson’s Ratio, Volume of Binder in Asphalt Mix (VB %), Shift factor between laboratory and in-service fatigue lives (SF) ,Performance Exponent(b), as material properties while traffic load Distribution (TLD) data and Reliability (R) required to calculate loading conditions. Shift factor (SF), performance exponent (b) and reliability(R) are the factors that have been recognized as factors varied upon the environmental factors in many researches. However, Reliability is considered as a kind of safety factor in AUSTROADS and lower the reliability, thinner the Pavement layers and lower the capacity pavement structure. This may lead to lower the durability. In AUSTROADS Performance exponent has been taken by performing series of tests for different materials and Conditions. Under this conditions, main consideration paid for finding Suitable Shift factor for Sri Lankan conditions. Conditions of Empirically designed roads are taken in to consideration in finding the variation of pavement capacity while varying the Shift factor, reliability and Damage Exponent. Suitable shift factor value has been derived in the research while observing the behavior of Reliability and damage Exponent.
item: Conference-Full-text
Multi criteria analysis to prioritize the user expectation at traffic signals
(IEEE, 2024) Saranjan, P; Bandara, JMSJ
Traffic signals regulate complex traffic situations and aim to ensure that all road users safely pass the scenario and provide an orderly traffic flow. Discrepancies between road users at traffic signals can have an impact on the smooth flow of traffic and the effectiveness of travel. It is important to understand the user expectations at traffic signals and identify the most prioritized expectations. This study aimed to identify and prioritize the user expectations at traffic signals considering different user groups. Expectations of different user categories on safety, delay and ease of use were identified through a literature review. A survey was conducted to understand the priorities for the above-identified categories and parameters. This study obtained responses from 357 participants via a questionnaire survey. Collected data were analysed using the multi-criteria analysis. From the analysis, it was found that all road users prioritize safety more than delay and convenience of use. Drivers and passengers give more importance to user violations during red-light signals, jaywalking (crossing the road illegally) and high speed at the end of the amber period for when considering the safety parameters. Further, expectation differences in each subset of groups were analysed by considering age, gender and mode of travel.
item: Conference-Full-text
Understanding omitted facts in transformer-based abstractive summarization
(IEEE, 2024) Panawenna, PH; Wickramanayake, S
Text summarization is a natural language processing task that generates concise document summaries. It can be extractive or abstractive. The former extracts pieces of the document, while the latter generates new concise sentences after identifying the critical information from the input text. Abstractive Summarization (AS) more closely represents how a human would summarize and is used in multiple missioncritical downstream tasks in domains such as law and finance. However, the existing state-of-the-art AS models are based on black-box deep learning models such as Transformers. Hence, the users of such systems cannot understand why some facts from the document have been included in the summary while some have been omitted. This paper proposes an algorithm to explain which facts have been omitted and why in Transformerbased AS. We leverage the Cross-Attention (CA) in transformers to identify words in the input passage with minimum influence in generating the summary. These identified words are then given to a Large Language Model along with the input passage and the generated summary to explain the omitted facts and the reasons for omissions. The experimental results using the state-of-the-art AS model show that CA can help provide valuable explanations for the model’s fact selection process.
item: Thesis-Full-text
Study of driver behavior at entrance ramps of expressways in Sri Lanka
(2023) Ratiyala, DS; Mampearachchi, WK
Driver behavior characteristics have a significant influence on the design of an expressway interchange ramp terminal in relation to traffic safety. In general, ramp terminals are more prone to accidents because of their function, which includes traffic merging, diverging, and changing lanes more frequently. These factors increase driving anxiety and lead to more accidents. In addition, due to the adoption of various design standards in various projects, the ramp terminal lengths of Sri Lankan expressways differ from one another. The primary goal of this research is to examine how drivers behave at the entrance ramp terminal in relation to crucial influencing elements such as vehicle entry speed, ramp terminal entry zone, and expressway through traffic speed at the proximity of the entrance ramp terminal. The research also aims to explore ways to enhance drivers' behavior in this context. Six interchanges - Kerawalapitiya, Kothalawala, Kottawa, Galanigama, Pinnaduwa, and Godagama - were selected for further study based on the variation in acceleration lane lengths among them. The study utilized video data from a Closed-Circuit Television camera installed at the Kottawa Interchange on 27 February 2020. CCTV cameras were not available at the other five Interchanges; a drone survey was carried out at those locations on 14 October 2020. The analysis was based on two important parameters identified through a literature survey: 1. Vehicle entry speed to the expressway and 2. Vehicle entry zone to the expressway through the entrance ramp terminal. The speed of the vehicles as they enter the expressway is significantly lower than the speed of expressway vehicles, except at Godagama Interchange, according to the analysis. The entry speed into the expressway is 60 kmph on average for all six interchanges. This necessitates a larger space between oncoming expressway traffic and entering traffic using the acceleration lane. Another significant aspect was that the vehicles entering the expressway did not use the expressway acceleration lane as anticipated. At the Kottawa Interchange, a higher percentage of vehicles entering the expressway (20%) was observed beyond the ramp's tapering. In violation of the safety regulations, 27% of vehicles at the Godagama Interchange entered the expressway in the chevron area. When all interchanges are considered, only 50% of the vehicles entered the expressway through the designated zone, while the remaining 50% using the ramp taper, the chevron region, or beyond the ramp taper. The research results support the conclusion that drivers lack the necessary knowledge to use the expressway ramp terminal, as revealed through a careful investigation of driver behavior, including how they enter the expressway and at what speed. In order to educate the drivers before they enter to the expressway The phrase "Prepare for the Expressway Speed" has been selected as the appropriate wording for the signboard as a result of a survey that was conducted among design engineers involved in the field of geometric design of roads in Sri Lanka. Additional variable speed signboards displaying from ramp speed to expressway speed along the ramp have been identified as a secondary measure to promote uniform speed at the expressway entrance. Based on the research results, it is recommended to inform drivers about the expected way to enter the expressway through the entrance ramp terminal using signboards, television programs, or printed media.
item: Thesis-Full-text
Analysis of roadside air pollution in western province of Sri Lanka
(2025) Karunarathna, SWBS; Perera, L
Air pollution is now one of the largest issues in the world that is leading to climate change, global warming, more frequent whether extremities, and respiratory related fatalities. Vehicle exhaust is one of the primary causes of air pollution and it emits CO2, NO2, SO2, and Particulate Matter (PM) among other air pollutants. Even though some of these targets and standards are being established by the World Health Organization (WHO) to limit the concentration levels of such toxic pollutants globally, no such clear system is yet visible to achieve such targets in Sri Lanka.
As a starting point, the objective of this research is to analyze the level of roadside air pollutants in the Western Province of Sri Lanka and to identify the annual variation of roadside air quality parameters. Followed by the development of a model to understand the correlation between road traffic and roadside emissions with the intention of proposing mitigation measures to control air pollution.
Air quality data from 40 fixed locations from 2013 to 2018 were collected and spatial analysis was carried out. NO2 and SO2 concentrations are analyzed using Arc GIS software and heat maps were generated visualizing the spatial distribution of pollutant concentration in the Western Province of Sri Lanka to identify critical locations with low air quality. Based on the spatial analysis results, it was observed that most of the urban areas have very high concentration levels of NO2 and SO2 which exceed more than twice the standard concentration level (WHO Air Quality Guideline-2005) during the period of measurements. It was also observed that from the year 2013 to 2017 there was a gradual decrease in NO2, and SO2 levels in the Western province although, in the year 2018, there was a sudden increase in NO2 and SO2 concentration levels.
In addition, roadside air quality data was collected in conjunction with traffic data from 2022 to 2024 at eight selected locations to identify the distribution of pollutants away from the road and up to about 75m distance from the road edge. Based on the results of additional locations it is clear that NO2, PM2.5, and PM10 show a positive correlation with traffic data while CO2 shows some deviation during daytime at some locations