ICAHETS - 2011

Permanent URI for this collectionhttp://192.248.9.226/handle/123/19001

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item: Conference-Abstract
Proceedings of Advances in Highway Engineering & Transportation Systems 2011 [Pre Text}
(Department of Civil Engineering, 2011-07) Pasindu, HR
item: Conference-Abstract
A large scale test system to investigate mse soil reinforcement- backfill interaction
(Department of Civil Engineering, 2011-07) Jayawickrama, PW; Lawson, WD; Wood, TA; Pasindu, HR
Mechanically Stabilized Earth (MSE) retaining wall systems represent by far the most widely used type of retaining wall used by the transportation industry in the United States. These retaining walls have three primary components: (a) wall facing, (b) soil reinforcement and (c) select granular backfill. Precast concrete panels with typical dimensions of SftxSft are most commonly used as wall facing while galvanized steel strips and grids are most common among soil reinforcement. The integrity of these wall systems relies heavily on proper interaction between soil reinforcement and the granular backfill. More specifically pullout resistance of the reinforcement that is embedded in the backfill is an important design parameter that controls the internal stability of the wall system. In routine design practice, the pullout resistance is estimated based on semi-empirical equations that have been developed based on available test data. However, there are several drawbacks in the use of such semi-empirical equations. First, these semi-empirical relationships represent a broader range of backfill including some low quality material. Therefore, they generally provide pullout resistance estimates that are too conservative. Secondly, most of the pullout test data have been obtained from small scale test systems and therefore may not correctly simulate actual reinforcement-soil interaction that may occur under field conditions. Finally, none of the testing conducted to date has investigated alternative reinforcement configurations used in the field to circumvent obstructions behind the wall facing. This paper will describe a large-scale pullout test program conducted at Texas Tech University to fill the gaps in existing knowledge base. This pullout test system used has dimensions of 12ft xl2ft in plan and 4ft in height. It can accommodate 3 layers of soil reinforcement in a single filling. The pullout test system has the capability to simulate 40-ft of soil overburden. This is accomplished by placing 9 pressure plates, each 4ft x4ft in size over the soil and by pressurizing a series of hydraulic jacks between the plates and reaction beams. The test program included two different types of soil reinforcement; (a) 2-in wide, 160- mil thick ribbed steel strips, and (b) steel grids with varying sizes of longitudinal and transverse bar sizes and spacings. The paper will provide a detailed description of the test system, test procedure and provide an overview of significant findings from over 250 pullouts tests that have been completed to date.
item: Conference-Abstract
Design of rigid pavement joint spacing for rural roads.
(Department of Civil Engineering, 2011-07) Karunarathne, AMAN; Mampearachchi, WK; Nanayakkara, SMA; Pasindu, HR
When it is compared with the flexible pavements, tensile stresses along the pavement layers are more significant in rigid pavements. Shrinkage stresses and thermal stresses are the dominant contributors to develop the tensile stresses in rigid pavements. Providing lateral joints in appropriate spacing is one of the better solutions to overcome the said stresses. Rigid pavements are usually exposed to solar radiation severely and this incorporates with the development of varying thermal stresses as well. Rate of receiving heat flux from solar radiation, thermal properties of concrete and heat loss from concrete due to convection parameters of surrounding are the main influences of the temperature variation of an exposed concrete slab. This research produces a methodology to incorporate the temperature variation of concrete slab by the use of a 3D finite element model (FEM) approach, to estimate the relevant deformation of concrete due to its exposure to the solar radiation. ANSYS (Version 12.0.1) was used for this FEM analysis, to obtain thermal variations of an exposed pavement slab. Laboratory scale slab was used to verify the results obtained from the FEM. Verified FEM is capable of producing the lateral stresses and its corresponding deformations of concrete pavement for daily thermal variation. Lateral deformations due to shrinkage effect were calculated according to the BS 8110 part 2:1985 shrinkage model. Opening of the joint crack is restricted by the load transfer requirement in consecutive pavement slabs. Aggregate interlocking is an efficient load transfer mechanism for the thin concrete pavements which are commonly used in rural roads. Effectiveness of aggregate interlocking mechanism depends on strength of the concrete, strength of aggregate, maximum aggregate size, friction of cracked surfaces, slab thickness and joint opening. Lateral joint opening vary with the pavement life and it is directly affected to the Load Transfer Efficiency (LTE). Another key aspect of this study is to carry out an experimental investigation to obtain a relationship between crack width and LTE in a rigid pavement joints. 150 mm thick test concrete pavement slab was cast with grade 25 concrete, 20 mm coarse aggregate was used to obtain the LTE at cracked joint. Standard single axel, single wheel load of 40 kN was used to simulate the tire load. From the obtained results, it was observed that LTE decreases nonlinearly with the increase of crack width. This paper describes a procedure to obtain the joint spacing for thin rigid pavements by the use of the FEM results and LTE experiment outcome. According to the study, joint spacing for rigid pavements in rural areas can be provided even beyond the specified values of ACPA.
item: Conference-Abstract
Role of 3d-finite element modelling in the analysis of soil-structure interaction problems
(Department of Civil Engineering, 2011-07) Senanayake, A; Jayawickrama, PW; Lawson, WD; Pasindu, HR
Engineering design and analysis often rely on simplified models. These models are convenient and practical for use in routine applications. However, they have many inherent limitations. Most significant among these limitations are their inability to model the following: (a) the true non-linear, material behavior, (b) actual construction sequence, (c) dynamic effects of moving traffic loads, (d) the actual 3- dimensional configuration of the structure and (e) 3 dimensional the loading pattern. As a rule, these simplified analysis methods rely on assumptions that are conservative. But sometimes the degree of conservatism can be unacceptably high. This paper describes a research study that used a 3D FEM to find an explanation for apparent disagreement between simplified model predictions for the load rating of highway culverts and results from field inspections of these culverts. When highway reconstruction projects involve widening or change in elevation of roadways, highway agencies are required to reevaluate existing culverts using AASHTO culvert load rating procedures to verify their structural adequacy. Such reanalysis often indicate that the existing culverts are structurally deficient and therefore must be replaced or retrofitted. However, inspections conducted during replacement of the old culverts show that these structures are in sound structural condition and have no significant distresses. This implied that the existing load rating methods were too conservative and new guidelines were put in place in 2009 based on research conducted by the Texas Tech University. One key aspect of this research was to understand how soil-structure interaction affects culvert performance and how these effects may be included in the load rating procedure. The revised guide suggested the use finite element (FE) models of different levels of sophistication to help analysts in load rating. Furthermore, the guide states although 2D FE models with simplifying assumptions are acceptable for load rating purposes, they are not capable of predicting the culvert performance completely and recommends the use of 3D models for further research. Hence, this study employed a 3D FE model which simulated the behaviour of the culvert, the surrounding soil and the pavement as one whole unit under the exact 3D wheel load configurations applied in the field testing in an attempt to predict culvert behaviour more accurately. The FE model was built using ANSYS Workbench and allowed for project-specific input values, soil-structure interaction and was equipped with parametric analysis capability. The 3D FE model was then fed with site specific input parameters determined from detailed site characterization tests. As expected the 3D FE model was able to predict the deformations in the culverts far more accurately than the 2D models. The model was then used to carry out a sensitivity analysis to determine how parameters such as soil and pavement stiffness influenced the structural performance of the culvert.
item: Conference-Abstract
Stiffness based construction quality evaluation for pavement subgrade and base applications
(Department of Civil Engineering, 2011-07) Bandara, S; Pasindu, HR
The success of any pavement construction project depends on using durable materials as well as following proper construction practices. Durability of the pavement depends on selecting proper materials to meet design material properties and constructing pavement layers to achieve design strength properties. Pavement layer strength generally measured using deformation characteristics in terms of elastic modulus or resilient modulus values. Both AASHTO 1993 empirical pavement design guide and the new mechanistic pavement design guide use subgrade soil resilient modulus as a primary design parameter. However, during pavement construction subgrade and base construction quality measurements are routinely measured in terms of field density and moisture content. This is the accepted method for most of the highway agencies in the world. The main reason for this practice is the long history and experience of using density/moisture measurements for compaction control and also lack of proper field measuring equipments for modulus measurements. Due to recent interest in mechanistic based pavement designs, an interest is gaining towards using design parameters such as resilient or elastic modulus for construction quality control and acceptance. Several highway agencies such as in United Kingdom and Germany extensively evaluated several portable field devices for subgrade and base construction QA/QC. These devices include Light Weight Deflectometer (LWD) GeoGauge and Dynamic Cone Penetrometer (DCP). In the USA, several states have started evaluating these devices for pavement construction QA/QC. This study is aimed at evaluating DCP and LWD as a pavement construction QA/QC tool. The objectives of this study are (i) complete literature search for using stiffness measurements for pavement construction quality evaluation (ii) determining the in-situ stiffness values based on DCP and LWD on number of construction projects (iii) compare and contrast the stiffness measurements with density and moisture content measurements. This paper will include the literature search portion of the project and some preliminary results of stiffness measurements and density/moisture content measurements on few construction projects.
item: Conference-Abstract
Regular bus service or regular plus express bus service? analysis of mode succession in a public transit corridor
(Department of Civil Engineering, 2011-07) Thilakaratne, RS; Wirasinghe, SC; Hubbell, J; Pasindu, HR
Many transit corridors experience significant delays and are often operating at or near capacity; A single mode may not be able to provide either the required capacity or improved Level of Service (LOS) in major, heavily traveled corridors. As a result the transit modes may not be well accepted by the travelling public. Transportation improvements are needed in order to meet growing travel demands, sustain mobility and reduce congestion in developing corridors. The concept explored in this paper is a mode evaluation for transition from low performance to high performance transit technologies. The basic alternative transportation modes, Regular Bus, and Regular plus Express Bus, are realized through an elementary analytical model for evaluation of transit modes which can be further applied for other higher order transit modes. The characteristics of transit modes such as speed, capacity, dynamic properties, operating costs, loading/unloading times and feeder systems are mathematically assessed. This model optimizes the mode selection and evaluates the best possible transition point in terms of transit system requirements for both the users (in terms of waiting and riding time), and operator for a given corridor over time. It encourages transit users and operators to select a better mode of service with significant impacts on level of service, capital and operating costs, and transit market development.
item: Conference-Abstract
A revisited model estimation for international passenger demand at Bandaranaike international airport, Sri Lanka
(Department of Civil Engineering, 2011-07) Piyathilake, LWD; Priyadarshani, GAC; Bandara, JMSJ; Pasindu, HR
Regression models are quite commonly used in air travel demand estimation. This paper presents a passenger forecast model for the Bandaranaike International Airport, which is the single international gateway for passengers travelling in and out of Sri Lanka at the time of conducting the study. The study hypothesize that the parameter estimates for the demand determinants of air travel in Sri Lanka has changed overtime and the model estimation revisit the analysis carried out by Bandara and Wirasinghe (2001) to estimate passenger demand for medium sized airports. Post fact analysis of the model proposed by Bandara and Wirasinghe (2001), revealed statistically significant differences between prediction and actual values with outliers to the 95% confidence interval bands established for the regression model. The deviations were results of the effects of 9/11 incident and heightened civil unrest experienced time to time in Sri Lanka during the past ten years. An empirical validation to the existing model was identified as necessary, since Sri Lanka is at the juncture of post war development proposals to promote the country as an aviation hub. A further objective of estimation was to justify the best time scale of past data to be used in model calibration for passenger demand forecasting using econometric models. The new estimates are established using a multiple regression model with two variables; Real Gross Domestic Product (RGDP) and a Dummy (TJ variable for severe terrorism/civil unrest conditions. Findings of the previous study is revalidated empirically by concluding that using 12-15 year past data for model calibration meets multiple regression assumptions at its best with time series data, avoiding spurious regression. The results suggest that the model forecasts ideally fits with the actual in the medium term. Hence, updating the model on a roll-out basis increases the validity of the model estimates.
item: Conference-Abstract
Impact of transfer on transit attractiveness
(Department of Civil Engineering, 2011-07) Pasindu, HR
Walking from origins to transit stops, transferring between transit lines and walking from transit stops to destinations—all add to the burden of transit travel. Transfer, in particular, has been shown to produce an additional penalty that is independent of time that it takes to transfer. Riders usually have a negative perception of transfer because of the inconvenience which can be termed as "transfer penalty". This transfer penalty is composed of several components: penalties due to walking while transferring, due to waiting for the connecting vehicle, extra cost and uncertainty. Some of these attributes of the transfer are often lacking in most of the existing literature. Understanding what impacts the transfer penalty and the contribution of each component can have significant implications for a transit authority, helping to identify which types of system improvement can most cost-effectively improve transfers, and thus attract more passengers. Such an understanding should also lead to potential improvements in ridership forecasting models. This paper describes an investigation of the impact of transfer on transit mode choice by decomposing the transfer penalty into transfer walking distance and transfer waiting time. The approach is to consider alternative utility functions with different representations of the transfer component and subcomponents, including piecewise-linearand separated formsforthe sensitivity parameter. The empirical data used were obtained in stated preference experiments of transit mode choice comparing LRT and bus. Alternatives were described by specifying the amounts of time spent on vehicle, access, transfer and egress walk distances, fare, and transfer wait time. Indications of socioeconomic characteristics and level of experience of transit use were also collected. A total of approximately 452 interviews were collected in April of 2010. These were used to estimate the parameter values for a range of different utility functions in logit models representing choice behavior. The Jack-knife estimation procedure was used to correct for the repeated measurements. The results indicate, among other things, that a transfer is equivalent to about 25 minutes of ride time, that walking at transfer is more onerous than waiting at transfer, that 'per minute' sensitivity to transfer wait time goes down as time goes up, that transfer becomes more onerous for aged people, for female and for new users. Some of these findings are novel while others are consistent with work done previously, and these findings have some implicationsfor both theory and practice.
item: Conference-Abstract
Pedestrian facilities in urban environments using "walkability" measures
(Department of Civil Engineering, 2011-07) Dias, I; Bandara, JMSJ; Pasindu, HR
Pedestrian facilities in urban environment are sometimes less appealing in residential/ recreational areas or insufficient to serve the peak hour pedestrian flows in commercial areas .There is no proper mechanism to evaluate the deficiencies in pedestrian facilities. Furthermore, increasing trend in motor vehicle use and pedestrian related accidents are the evidence of inadequate facilities for pedestrians. This research proposes a scoring model to evaluate pedestrian facilities in urban environment using "Walkability" measures. Walkability is an idea of quantifying the safety and desirability of walking routes. The model can be used to evaluate pedestrian facilities in road links to compare different road links or to identify deficiencies in a given road. At present walkability is evaluated using qualitative measures that are very subjective. Existing methods of evaluating walkability was carefully studied and the limitations and weaknesses were identified. Methods to evaluate as many features were proposed and validated. Among these factors, several features of sidewalks such as width, elevation difference, paving type and continuity are assessed. Modal conflict, the conflict between pedestrians and bicycles/ motorized vehicles is measured using passing and meeting number of events. Availability of crosswalks and delay at un-signalized and signalized crosswalks are some of the parameters used to evaluate crossing facility. A good mix of land use where the number of destinations (Groceries, restaurants, schools, health facilities, Cinemas, etc.) is higher is considered to be a good walkable neighborhood. Availability of pedestrian facilities including, benches, shades, bus halts with seats, pedestrian information boards, proper street lighting add scores to a road link. Addressing differently able people; the blind, the disabled, push carts, children is also taken in to consideration while universal accessibility is believed to be at vital importance. Apart from the above quantitative measures, parameters such as, aesthetics is also assessed qualitatively. A score as a percentage is finally obtained from the evaluation where 100% means a perfect road to walk and 0% means a disasterfor walking.
item: Conference-Abstract
Hydroplaning risk evaluation in high speed low traffic volume highways in developing countries
(Department of Civil Engineering, 2011-07) Jayasuriya, W; Gunaratne, M; Pasindu, HR
Hydroplaning occurs when water pressure builds up in front of and under a moving vehicle tire resulting in an uplift force sufficient to separate the tire from the pavement. The loss of steering and the drag force produced during hydroplaning may then cause the vehicle to lose control, especially when one of the steering tires is subjected to hydroplaning. During high intensity rainfall events, a significantly thick water film builds up on highway surfaces and the risk of vehicle hydroplaning increases with the water film thickness. It is known that travel speeds which usually exceed 50 mph can drop by ten percent (10%) during rain due to the decreased visibility and the drivers' perception of reduced traction. However, according to the current study, the effects of hydroplaning can be significant even at speeds as low as 45 mph. Vehicle speeds can be excessive in high speed facilities in developing countries due to low traffic volumes and lack of speed limit enforcement. Furthermore, since only a little attention is paid to pavement performance with respect to skid-resistance, there is a higher probability of the occurrence of this safety hazard when more and more high speed facilities are constructed in the developing world. Therefore, it is of utmost importance to incorporate the factors that contribute to hydroplaning in pavement management systems in developing countries. It is known that the vehicle speed at incipient hydroplaning depends on the water film thickness (WFT), tire pressure, tire tread depth, pavement texture, and several other secondary factors. The effects of the water film thickness in crown and transition sections are the primary factors investigated in this study. The water film conditions are quite different in super-elevation transition sections compared to normal crown sections. The combined effects of lateral and longitudinal slopes in super-elevation transition sections cause a significant increment in WFT. And the magnitude of the maximum WFT increases at super-elevation transitions compared to normal crown conditions while the location of the maximum depth varies with the longitudinal slope. Furthermore, with regard to vehicle safety at superelevation transitions, it is not clear whether the magnitudes of WFT or changes in WFT in the longitudinal and lateral directions are the more critical variables. All in all, it is realized that hydroplaning can present a severe safety issue at transition sections than at the normal crown sections. In the research described in this paper, a number of field trials were conducted at first to verify the existing correlations developed by previous researchers. Finally due to the relative contributions of a number of different causative factors involved in hydroplaning and the great deal of uncertainty in the initiation of this phenomenon, the hydroplaning risk is evaluated in terms of a probability.
item: Conference-Abstract
Low cost speed management in high speed rural roadways: optical speed bars
(Department of Civil Engineering, 2011-07) Dissanayake, S; Balde, A; Pasindu, HR
Despite considerable safety measures implemented by traffic and transportation engineers, speeding continues to be a significant safety problem on the highway network, both in the United States and other countries. Even though higher traffic volumes and more travel occur in urban areas, majority of fatal crashes occur in rural areas indicating the significance of the issue. When high-speed roadways pass right through the small towns in rural areas there are considerable drops in speed limits, making proper speed management critically important. However managing speed has always been a challenge particularly in rural communities due to the low budgets available leading to lower levels of enforcement. It is therefore necessary to identify effective, low-cost approaches to control speeds in such areas. Optical Speed Bar (OSB) treatment is one such approach, where transverse pavement makings are put in place with gradually deceasing spacing giving the drivers the perception of going faster than they actually are traveling. This research attempted to evaluate the effectiveness of OSBs in reducing approach speeds on two-lane, rural divided highways approaching small communities. Each approach had one lane and speed drop was either from 65 mph to 45 mph (4 sites) or from 55 mph to 30 mph (1 site). Speeds data were collected and analyzed both before and after installation of the optical speed bars at the five ssites. Effectiveness of the bars was evaluated using changes in mean and 85* percentile speeds under different categories by considering all vehicles, vehicle classification (two axles vs. more than two axles), days of the week (weekdays vs. weekends), and time of day (daytime vs. nighttime). The t-testforthe sample mean and the F-test of variance were used to determine significant differences in speeds among datasets. Significant reductions in mean speeds and speed variance were observed at the end of the OSBs at four of the five sites, and one site showed no statistically significant change in speeds. Speed reductions were higher during daytime and weekdays. Higher speed reductions for twoaxle vehicles were observed, with the exception of one test site. Daytime speeds and speeds of two axle vehicles decreased the most at almost all test sites. However speeds analyzed farther downstream of the treatments gave indication that speed reductions were not maintained for a long distance. However, when considering the low cost associated with the treatment, optical speed bars might be a good solution to control approach speeds in small communities.
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
Decision making framework for transportation infrastructure selection
(Department of Civil Engineering, 2011-07) Attanayake, U; Mohammed, AW; Hu, Y; Abudayyeh, O; Aktan, HM; Pasindu, HR
The world transportation system matures day-by-day wherein the congestion growth rate is alarming while its infrastructure growth has slowed down, which affects the quality of life. Developing highway infrastructure by utilizing modern technology and knowledge is vital for successful completion of the projects with least impact to traffic and local economy. Accelerated construction technology is developed to minimize construction duration; hence, to mitigate congestion, reduce on-site environmental impacts, and to improve the safety of stakeholders. Selection of construction methods and technology is based on available funding, proposals from contractors or design-bid-build contracts that lack many of the factors which should tangibly control the decision of type of facility to be constructed. The decision group comprising of representatives of owner agency and contractor with differing preferences, experiences and background requires a framework to negotiate among them to arrive at an optimal decision for a particular project. The available decision making frameworks include several simple "Yes"/ "No" answer questions that do not consider relative importance among the factors providing a transparent methodology or a tool to arrive at the decision. In addition, potential constraints are not addressed to identify structural systems/configurations with respect to their performance and construction techniques/technologies for implementation at specific sites. A multicriteria decision making framework is presented in this paper using highway bridge construction as an example. The framework is developed using Analytical Hierarchy Process (AHP) and accommodates many quantitative and qualitative factors identified through interviews and review of literature including post-construction and lessons learned reports.
item: Conference-Abstract
The influence of destination factor and transportation system factor to choice the shopping location
(Department of Civil Engineering, 2011-07) Tonny, J; Pasindu, HR
Work trip is not flexible trip as like shopping trip where are the travel destination has choice characteristic. In the urban area, the shopping trip is one of the biggest trip generation, and a push factor of urban sprawl, thus if we control this trip type will gives us positive effect to decrease the environmental impact of the transportation. The variation of the facilities, type of goods, quality of the products, and the action attraction which offered by a shopping centre will become as attraction factors, it difference with the work trip. The knowledge of this shopper attitude to percept the attributes of a shopping centre or retail centre will become importance to understand why they choose that shopping centre, so it will attract the shopper to trip from their origin to that shopping centre not to the other. Through household trip role research in Bandung by home interview and Multi-Criteria Analysis (AHP) methods can reach to understand the sensitivity of the transport system attributes and shopping centre location attributes to the individual shopper attributes, thus it can make easier to understand the relationship between land use and transportation in order to control the shopping trip to reach efficiency and effectively the shopping centre services. As result of this study, it appears for daily and non daily shopping, the travel cost (xn) and travel time (xj attributes of transport system factor, and the satisfaction level (x2S) than level of services attributes (x22) of the shopping centre location factor, become to the most dominant attributes in shopping centre choice for all age and wage group. This research implication is the shopping centre plan in Bandung and the others cities as well, not only base on the accessibility and services scale, but also must be planned base on the socio-economic characteristic of the citizen as the consumers.
item: Conference-Abstract
It based evacuation methodology for a coastal railway system under a tsunami warning
(Department of Civil Engineering, 2011-07) Sirisoma, RMNT; Wirasinghe, SC; Pasindu, HR
Natural disasters have been known to humans ever since the formation of early civilizations. However, as increased human interventions contribute to the destabilization of the natural balance of environmental processes, even more frequent occurrence of natural calamities are occurring today. Prediction, prevention and planning/installing, detection/warning systems are very important components before a disaster. The evacuation procedure should start only once the tsunami arrival information is confirmed. Since Sri Lankan coastal railway lines typically do not have branch lines running inland, trains cannot be detoured during the evacuation procedure. Thus, the in-line evacuation process should be well planned and guidelines made known to the operator and the users. In this study, the South-West coastal railway line in Sri Lanka is analysed to identify the operation & evacuation of trains under a tsunami warning. The "safe" railway stations are identified depending on the station elevation with respect to the mean sea level, the capacity to store trains, and the number of tracks. It is assumed that, at a minimum, the railway control centre can be equipped to detect, and communicate with, all the trains and stations along the coastal line at any instance. The nearest "safe" and "unsafe" railway stations for each train, and the travel time to them, are determined with respect to the location and direction of each train atthe warning time. Travel times to each station are analysed depending on the distance and possible speed of a train. If there is sufficient time, trains are directed to a safe station; otherwise, to an unsafe station. If a train is sent to an unsafe station, passengers must be evacuated immediately. Short notice of a tsunami may also require evacuation of passengers at the nearest possible safe evacuation location, due to lack of time to reach any railway station. A methodology is proposed to identify the operational control of trains under different tsunami warning times, wave heights and locations of trains relative to stations. The confusion and concern that will prevail among passengers is considered. The poor communication and signal systems in place are considered. Planning guidelines are proposed to improve communication, select safe stations under various tsunami scenarios, as well as select evacuation stations. A procedure for assigning trains to safe or evacuation stations is also advanced.
item: Conference-Abstract
Stepwise genetic fuzzy logic signal control under mixed traffic condition
(Department of Civil Engineering, 2011-07) Chiou, YC; Huang, YF; Pasindu, HR
Adaptive traffic signal control typically feeds the real-time traffic data, collected by the sensors, into a build-in controller to produce the timing plans. Thus, it can provide signal-timing plans in response to real-time traffic conditions. Numerous adaptive signal control models have been proposed, especially, fuzzy logic control (FLC) based signal control models are popular. Most of FLC-based signal control models subjectively preset logic rules and membership functions without an optimal learning algorithm. Adjusting the combination of logic rules and membership functions very often requires tremendous efforts, but there is no guarantee to obtain good control performance. Genetic algorithms (GAs) have been proven suitable for solving both combinatory optimization problem (e.g., selecting the logic rules) and parameter optimization problem (e.g., tuning the membership functions). Employing GAs to construct an FLC system with learning process from examples, hereafter termed as genetic fuzzy logic controller (GFLC), can not only avoid the bias caused by subjective settings of logic rules or membershipfunctions but also greatly enhance the control performance. Most previous GFLC studies, however, have employed GAs either to calibrate the membership functions with preset logic rules, to select the logic rules with given membership functions, or to learn both logic rules and membership functions iteratively. Thus, the applicability of that GFLC is very likely reduced. However, to simultaneously or sequentially learn of logic rules and membershipfunctions may require a rather lengthy chromosome and large search space, resulting into poor performance, a long convergence time and unreasonable learning results (i.e. conflicting or redundant logic rules, irrational shapes of membership functions). To avoid these shortcomings, this paper proposes a stepwise evolution algorithm to learn both logic rules and membership functions. At each learning process, the proposed algorithm selects one logic rule which can best contribute to the overall performance controlled by previously selected logic rules. Such a selection procedure will be repeated until no other rule can ever improve the control performance. Therefore, the incumbent combination of logic rules is the optimal learning results. To facilitate the learning process of the stepwise GFLC-based signal control model, the cell transmission model (CTM), a mesoscopic model proposed by Daganzo (1994, 1995), is used to evaluate the performance of learned logic rules and membership functions. In addition, the conventional CTM was designed for pure traffic, which is not applicable for many Asian urban streets where mixed traffic of cars and motorcycles is prevailing. Thus, this study also proposes mixed traffic cell transmission models (MCTM) to replicate the behaviors of mixed traffic. To validate the proposed SGFLC model, case studies on the signal control of isolated intersection and sequential coordinated intersections are conducted, respectively. For the case of isolated intersections, the results show that in terms of total vehicle delay, the SGFLC model performs best in comparing to pretimed signal control and queue length-based adaptive control models. In the case of sequential intersections, the results consistently show that the SGFLC model performs best, no matter which coordinated signal system (i.e. progressive, alterative, and simultaneous) is operated.
item: Conference-Abstract
Geometric design standards for narrow curves in hilly terrain of Sri Lanka
(Department of Civil Engineering, 2011-07) Salawavidana, SAST; Pasindu, HR
Geometric designs of national roads in the remote areas of Sri Lanka are involved with the economic constraints. Therefore, following the accepted design standards is not practical in many of the occasions. The reasons for this are narrow curves, steep grades and the combination of the both. Funds are not readily available for improvement of these narrow curves in remote areas to suit the accepted design standards. In such circumstances the design engineer is compelled to go for substandard designs. This is not an acceptable practice because such substandard designs lack the reliability and integrity of the design process that is a prime objective of any design standards. The minimum design speed is 30kmph and the minimum curve radius is 25m in the conventional highway design practice as used in Sri Lanka, which is a combination of AASHTO and AUSTROADS. But it is common to find curve radii lesser than these values. There is no such design standard for narrow curve design relevant to Sri Lankan conditions at present. But in other countries, low speeds are used to design the curves. Those design standards cannot be used in Sri Lanka as it is because they use different parameters and assumptions compared to Sri Lankan Standards. In this research, such a design standard was derived using the concept of Factor of Safety in minimum curve radius. With this design standard, it is possible to extend the lower margin of the radii range up to 13m and the lower margin of the design speeds up to 20kmph.Further, a suitable vertical design standard has been derived to cater the above horizontal design standards.
item: Conference-Abstract
Developing a comprehensive mode choice model to capture the preferences for mass rapid transit in Dhaka
(Department of Civil Engineering, 2011-07) Enam, A; Choudhury, CF; Pasindu, HR
Dhaka, the capital city of Bangladesh and the home of 15 million people, is subjected to acute traffic congestion on a regular basis resulting in lost productivity, fuel wastage, commuter frustration and environmental degradation. The city is perhaps the only megacity with no well organized public transport system and one of the very few ones without Mass Rapid Transit (MRT). In Strategic Transport Plan for Dhaka (STP, 2005) recommendations have been made to launch new MRT systems like Bus Rapid Transit (BRT) and Metro in order to strengthen the public transport system of the city. Planning of these new systems warrants comprehensive mode choice models that can help in quantifying the relative importance of attributes, determining the Value of Time (VOT) for cost-benefit analysis, predicting ridership, etc. The existing models however do not account for the deficiencies of existing data like missing choice sets, measurement errors in the level of service (LOS) data, lack of information regarding the new modes etc. and can lead to incorrect travel demand predictions. This has prompted the current research where Stated Preference (SP) data has been collected to capture the preference for proposed new alternatives (MRT), methodologies have been developed to address the other limitations of the existing data and a comprehensive mode choice model has been developed combining Revealed Preference (RP) and SP data. In the SP survey conducted in the research, respondents have been presented with choice scenarios that included BRT and Metro alongside their current modes. Different levels of three attributes (travel time, travel cost and waiting time or frequency) were used to describe the new alternatives. The attributes and associated levels were selected as the most important attributes as perceived by the respondents on the basis of the findings of an initial survey. To address the unobserved choice sets of the respondents in the available RP data a choice set generation model has been developed using SP data. The estimated parameters of the developed model have been used to predict the choice sets of the respondents in the RP data probabilistically. Regression analysis has been done to address the measurement errors of the travel time derived from network analysis Discrete choice models have been developed using the corrected RP data and the collected SP data and the coefficients of the utility parameters have been estimated using a maximum likelihood approach. The observed taste heterogeneity of the respondents have been taken into account by the introduction of socio-economic variables like income, age, gender, occupation, employment, etc into the model and market segmentation tests have also been performed. The VOT values from the combined model are plausible compared to the values obtained from previous choice models as well as the disjoint RP and SP models. Further, the methodologies proposed in the current research can be useful tool for transport related analysis in other developing countries facing similar data issues.
item: Conference-Abstract
Identification of factors related to state level safety belt usage rates in the United States
(Department of Civil Engineering, 2011-07) Dissanayake, S; Pasindu, HR
Safety and efficiency of the transportation system is extremely important for the economic development of any region. Safety record of the United States highway system is stagnating over the last several years with annual fatalities of around 41,000 and millions of injuries. Total economic cost due to these motor vehicles crashes has been estimated to be more than $ 230 billion based on National Highway Traffic Safety Administration's estimations. Transportation community is looking at various strategies for improving highway safety of road users with the intention of reducing these huge economic losses. Seat belt usage has frequently been identified as one of the most effective ways of improving highway safety in highly motorized countries. Seat belts are considered to be particularly useful in reducing fatalities. In the United States, even though mandatory seat belt laws have been widely regarded as one of the best ways of increasing seatbelt usage by motorists, some states still struggle with passing primary seat belt laws that could save many lives. While usage rates considerably vary among states with primary and secondary seat belt laws, there could be many other factors that affect usage rates in any given state. Examples of some of these other potential characteristics include level of urbanization, composition of roadway infrastructure, education level of the road users, number and/or percentage of minorities, gender and age distributions, penalty for seat belt violation, average income, and crime rates. While a change in seat belt policy seems like a more feasible way to achieve increased seat belt usage rates in a given state, it is not possible to accurately evaluate the impact due the seat belt policy without considering these other factors into consideration. Accordingly, this study developed statistical models to identify the factors that are determinants of state seat belt usage rates, which also quantified the effect of changing the law on usage rate. Data on seat belt usage for this study were obtained through the observational surveys conducted throughout each of the states in the United States. Findings indicate not only the benefits of primary seat belt law, but also identifies the critical user groups for whom more focused education programs could be developed. Additionally, more critical facility types were also identified where increased enforcement on which might bring the most effective results in terms of seat belt usage.
item: Conference-Abstract
Identification of safety issues of older drivers using survey data
(Department of Civil Engineering, 2011-07) Perera, L; Dissanayake, S; Pasindu, HR
In the past, many research studies have analyzed crash data to identify various factors contributing to older-driver over-involvement in crashes. However, it is also necessary to identify other types of safety related information which cannot be extracted from crash data, such as exposure to different weather and road conditions, difficulties associated with vehicle maneuvering, modifications made to driving patterns, etc., which might be playing a significant role in older-driver safety. Therefore, a questionnaire was prepared and a survey was conducted to identify those issues and difficulties highlighted in crash data. Based on the responses, a detailed examination was done to understand different behavioral changes in older drivers with respect to various conditions. Based on the survey results it was found that most of the older drivers have more than fifty years of driving experience and their seat belt usage was also found to be high. Left turns appear to be the most challenging maneuvering task. Analysis based on age revealed that level of difficulty associated with older drivers increase with age and similarly, preference to avoid demanding conditions, such as snowy weather, nighttime driving, and use of freeways has also increased with aging. Older drivers older than 70 years were highly involved in crashes and those with elevated income levels and education had higher involvement in crashes. Older male drivers indicated higher levels of difficulties in stopping, stopped waiting to turn, or slowing down situations. On the other hand, females showed higher levels of difficulty associated with identifying speeds and distance of oncoming traffic compared to males. Findings of this study could be used to develop more focused programs towards improving older driver safety.

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