ENGINEER - Vol. XLVIII, No. 04, pp. [page range], 2015 ENGINEER© The Institution - Vol. XLVIII,of Engineers, No. 04, Sri pp. Lanka [33-47], 2015 © The Institution of Engineers, 13. http://www.ietf.org/rfc/rfc3561.txt, Visited, 25. Lee, Y., Kouvroukoglou, S., McIntire, L. V., & 10th Dec 2014. Zygourakis, K., “A Cellular Automaton Design of a Flyover and Roundabout underneath it to Model for the Proliferation of Migrating 14. Conner, W. S., Kruys, J., Kim, K., & Zuniga, J. Contact-inhibited Cells”, J. Biophysical Journal, ease the Traffic Congestion at the Junction C., “IEEE 802.11s Tutorial: Overview of the Vol. 69, pp. 1284-1298, October, 1995. Amendment for Wireless Local Area Mesh P. L. Mututantri, W. D. P. Abeysinghe, L. S. S. Wijewardena and Networking”, IEEE 802 Plenary, 26. Alarcóna, T., Byrneb, H. M., & Mainia, P. K., November,2006. “A Cellular Automaton Model for Tumour K. S. Weerasekera Growth in Inhomogeneous Environment”, J. 15. Lui, J. C., & Baron, J., “Mechanisms Limiting Theoretical Biology, Vol. 225, No. 02, pp. 257- Abstract: Urban traffic congestion has become a serious concern of transportation professionals Body Growth in Mammals”, J. Endocrine 274, November, 2003. and traffic managers. Rajagiriya town becomes severely congested due to vehicular traffic during Reviews, Vol. 32, No. 03, pp. 422-440, June, daytime. Therefore, efforts were made to quantify this congestion and formulate appropriate 2011. 27. Mireira, O., & Deutsch, A., “Cellular measures to mitigate it. Rajagiriya town consists of several intersections located at close proximity to Automaton Models of Tumor Development: one another, and they have become potential sources of acute traffic congestion. There are three 16. Finkielstain, G. P., Forcinito, P., Lui, J. C., A Critical Review”, J. Advs. Complex Syst, Vol. junctions situated along the main road (i.e. Sri-Jayewardenepura road) namely Police station junction, 05, No. 2/3, pp. 247-268, 2002. Barnes, K. M., Marino, R., Makaroun, & Bo-tree junction and the Kohilawatta road junction. Baron, J., “An Extensive Genetic Program

Occurring during Postnatal Growth in 28. Wolfram, S., “Statistical Mechanics of Cellular Multiple Tissues”, J. Endocrinology, Vol. 150, Automata”, J. Reviews of Modern Physics, Vol. In order to find a solution to this traffic congestion, the capacities of the roads were evaluated by No. 04, pp. 1791-1800, April, 2009. 55, No. 03, pp. 601-644, July, 1983. compiling data related to prevailing vehicular flows and collecting other supportive information both as of today and for the next 20 years (i.e. up to the year 2035). From the capacity calculations made 17. Bryant, P. J., & Simpson, P., “Intrinsic and 29. Kari, J., “Theory of Cellular Automata: A from field data it is evident that all the roads in the area would fail to cater to the future traffic Extrinsic Control of Growth in Developing Survey”, J. Theoretical Computer Science, Vol. demands. Road widths, lanes and walkway shoulders were designed using the U. S. Highway Organs”, J. The Quarterly Review of Biology, 334, pp. 3-33, November, 2005. Capacity Manual so as to meet the anticipated traffic demands and pedestrian requirements of the Vol. 59, No. 04, pp. 387-415, December, 1984. future, [1]. 30. Barredo, J. I., Kasanko, M., McCormick, N., 18. Forcinito, P., Andrade, A. C., Finkielstain, G. &Lavalle, C., “Modelling Dynamic Spatial As a solution to ease the transportation problems mentioned, initiatives were taken to separate out the P., Baron, J., Nilsson, O., & Lui, J. C., Processes: Simulation of Urban Future “Growth-inhibiting Conditions Slow Growth Scenarios through Cellular Automata”, J. traffic flows by constructing a flyover. The design of the flyover was done considering a heavy traffic Plate Senescence”, J. Endocrinol, Vol. 208, No. Landscape and Urban Planning, Vol. 64, pp. 145- movement and the flyover was so located that it did not hinder the three junctions. The location for 01, pp. 59-67, January, 2011. 160, 2003. the flyover was decided based on the prevailing operating conditions. For the flyover, pre-stressed material was proposed as it is found to be economical whereas pre-stressed concrete and in-situ 19. Bullough, W. S., “Mitotic and Functional 31. Liu, Q.X., Jin, Z., & Liu, M.X., “Spatial concrete were proposed for the beams and piers respectively. Homeostasis:A Speculative Review”, J. Cancer Organization and Evolutional Period of the Research, Vol. 25, No. 10, pp. 1683-1727, Epidemic Model using Cellular Automata”, J. Roundabouts were found to be a suitable solution to manage the traffic flow under the flyover. The November, 1965. Physical Review E,Vol. 74, November,2006. roundabout design was done using a turning template and based on the Australian Standards

(AUSTROADS) [2]. The selection and the design of a roundabout, as with any intersection, require the 20. Onda, H., “A New Hypothesis on Mitotic 32. Li , X. B., Jiang, R., & Wu, Q. S., “Cellular Control Mechanism in Eukaryotic cells”, J. Automaton Model Simulating Traffic Flow balancing of competing objectives such as safety, operational performance, and accessibility for all Theoretical Biology, Vol. 77, No. 03, pp. 367- atan Uncontrolled T-Shaped Intersection”, J. users. Factors such as land use, aesthetics, and environmental aspects too were considered. Flexible 377, April, 1979. International Journal of Modern Physics B, Vol. concepts allow room for independent designs and techniques tailored for a particular situation while 18, No. 17-19, pp. 2703-2707, 2004. emphasizing performance based evaluation of those designs. 21. Lee, S. J., “Regulation of Muscle Mass by Finally a suitable layout plan was introduced for the study. Myostatin”, J. Annual Review of Cell and 33. Almeida, R. M., & Macau, E. E. N., “Stochastic Developmental Biology, Vol. 20, pp. 61-86, 2004. Cellular Automata Model for Wildland Fire Keywords: Flyover, Roundabout, Traffic flow, Traffic congestion Spread Dynamics”, Proc. 9th Brazilian 22. Elgjo, K.,& Reichelt, K. L., “Chalones: from Conference DINCON'10,pp. 249-253, June,2010. Aqueous Extracts to Oligopeptides”, J. Cell Cycle, Vol. 03, No. 09, pp. 1208-1211, 34. Martin, O., Odlyzko, A. M., & Wolfram, S., 1. Introduction September, 2004. “Algebraic Properties of Cellular Automata”, P. L. Mututantri, Undergraduate, Department of Civil Engineering, The Open University of Sri Lanka J. Communications in Mathematical Physics, Vol. The town of Rajagiriya, the area under study, 23. Bakthavatsalam, D., Brock, D. A., Nikravan, 93, pp. 219-258, 1984. administered by the Kotte Municipal Council W. D. P. Abeysinghe, Undergraduate, Department of Civil N. N., Houston, K. D., Hatton, R. D., & Engineering, The Open University of Sri Lanka. is situated about 10 km away from the centre Gomer, R. H., “The secreted Dictyostelium 35. Packard, N. H., & Wolfram, S., “Two- of , the commercial capital of Sri Eng. L. S. S. Wijewardena, BSc Eng. (Hons.) (Peradeniya), protein CfaD is a chalone”, J. Cell Science, Vol. Dimensional Cellular Automata”, J. Journal of M.Eng.(AIT), C.Eng., MIE(SL), MIHT(UK), Senior Lecturer 121, pp. 2473-2480, August, 2008. Statistical Physics, Vol. 38, No. 5/6, pp. 901- Lanka. There are supermarkets, schools, Grade I , Department of Civil Engineering, The Open religious places, educational centres, a University of Sri Lanka. 946, 1985. 24. Kansal, A. R., Torquato, S., Harsh, G. R., children‟s park and government and private Eng. (Prof.) K. S. Weerasekera,BSc Eng (), Chiocca, E. A.,& Deisboeck, T. S., “Simulated 36. http://elib.uni-stuttgart.de/opus/volltexte/ sector institutions located in this area. There MEngSc (UNSW), PhD (UNSW), FIE(SL), CEng, IntPE(SL), Brain Tumor Growth Dynamics Using a 2007/3120/pdf/khelil_diss.pdf, Visited, are three junctions in the town namely, “Police MIE (Aust), CPEng, MIHT(UK), MASCE, Chair and Professor Three-Dimensional Cellular Automaton”,J. 10thNov 2014. of Civil Engineering, Department of Civil Engineering, The station junction, “Bo-tree junction”, and Open University of Sri Lanka. Journal of Theoretical Biology, Vol. 203, No. 04, “Kohilawatta junction” (Figure 1)and all these pp. 367-382, April, 2000. 37. http://www.omnetpp.org/doc/omnetpp/ three junctions have been considered in this manual/usman.html, Visited, 10th Dec 2014. 1

8 33

study. Heavy traffic congestion is observed in travel times, increase fuel consumption, air the town of Rajagiriya during morning, pollution and accidents. When one roadway afternoon and evening rush hours. There are gets congested, drivers tend to use other many simultaneous and conflicting alternative routes which necessarily may not movements at these junctions. A motorist have been meant to be used by vehicles. approaching via Rajagiriya along Kotte Getting caught in these traffic congestions can road and - Rajagiriya road has to cause mental stress to the road users leading to undergo much inconvenience especially various health issues. during peak hours. During off-peak hours, the congestion is not that severe. In the morning, The present traffic signal system at the traffic flows mainly towards Colombo and in Rajagiriya junction is not working the evening, its direction reverses. The three satisfactorily. Even if it does work junctions mentioned above are the primary satisfactorily, it is functioning below the points that lead to this traffic congestion. expected standard and therefore is inadequate to ease the traffic congestion. In addition to The road sections under this study encounters introducing a sound solution for this issue, the huge traffic towards , Parliament implementation of a proper traffic signal road and also towards Obeysekarapura, system suitable for this geometry or an Borella and and on these road introduction of a flyover at the junction has to sections a large number of public transport be considered. Furthermore, an adequate buses ply along with hundreds of other number of lanes should be established a teach privately owned vehicles. Buses take a approaching intersection to cater to the considerably long time to pass Rajagiriya in expected traffic flows. moving towards Nawala and Kohilawatta. The three junctions hinder the flow of traffic along the main route thereby increasing traffic 2. Aim and Objectives congestion along the main route (i.e. Sri Jayawardhanapura road). The aim of this study is to observe whether the existing road capacities are adequate to cater to Many government offices and public the current traffic volumes and if found institutions outside the Colombo city centre inadequate to design the road and are located close to the study area resulting in intersections in such a way so as to cater to the an increase in the traffic flow(e.g. Sethsiripaya, anticipated future traffic. This study also hopes Isurupaya, Parliament etc.) to this area. to propose ways and means of improving the Vehicles arriving at these destinations use this roads by introducing appropriate road widths route daily leading to an increase in the daily and a few lanes in the study area to cope up traffic flow. The unavailability of dedicated with the traffic needs to provide a satisfactory parking lanes or slots compels the drivers to level of service. The outcome of this study is park their vehicles along the road, and this too expected to introduce a suitable solution to has contributed to the increased traffic ease the projected traffic congestion at the congestion. Police station junction, Bo-tree junction and Kohilawatta road junction.

Towards fulfilling this aim, the objective of the study would be to justify and design a solution for the safe movement of vehicular traffic at the Rajagiriya junction by paying attention to

Kohilawatta the following: Bo-tree junction junction (main junction) 1. Identification of peak hours based on available traffic data. 2. Conduct of turning movement surveys Police station junction of traffic at the respective junctions during peak hours on week days. 3. Identification of the road widths and Figure 1 - Location of the Study Area the number of lanes currently available to determine future Traffic congestion can cause several problems requirements. such as economic costs resulting from delayed 2 34

study. Heavy traffic congestion is observed in travel times, increase fuel consumption, air 4. Determination of the most suitable  Separating out traffic flows expected to the town of Rajagiriya during morning, pollution and accidents. When one roadway flyover layout with a twenty year life pass over the bridge and under the bridge. afternoon and evening rush hours. There are gets congested, drivers tend to use other span to ease out the traffic congestion  Calculation of the required number of lanes many simultaneous and conflicting alternative routes which necessarily may not at the junction, by taking into for the flyover bridge and the intersection. movements at these junctions. A motorist have been meant to be used by vehicles. consideration typical traffic growth  Checking LOS after a period of twenty approaching Borella via Rajagiriya along Kotte Getting caught in these traffic congestions can rates. years for the traffic passing over the flyover road and Nawala - Rajagiriya road has to cause mental stress to the road users leading to 5. Designing the roundabout to ease out and underneath the flyover to verify the undergo much inconvenience especially various health issues. the traffic underneath the flyover. future scenario. during peak hours. During off-peak hours, the 6. Carrying out the structural design of  Introduction of a roundabout underneath congestion is not that severe. In the morning, The present traffic signal system at the the proposed flyover. the flyover. traffic flows mainly towards Colombo and in Rajagiriya junction is not working 7. Proposing a final solution for the  Evaluation of the number of lanes required the evening, its direction reverses. The three satisfactorily. Even if it does work existing traffic related problems at the in the roundabout and turning movement junctions mentioned above are the primary satisfactorily, it is functioning below the Rajagiriya intersection. details. points that lead to this traffic congestion. expected standard and therefore is inadequate  Conversion of the number of vehicles to to ease the traffic congestion. In addition to Passenger Car Unit(PCU) values. The road sections under this study encounters introducing a sound solution for this issue, the 3. Methodology  Determination of the gap acceptance, huge traffic towards Battaramulla, Parliament implementation of a proper traffic signal capacity analysis and queuing delays in the road and also towards Obeysekarapura, system suitable for this geometry or an 3.1 Data Collection roundabout according to AUSTROADS Borella and Kollupitiya and on these road introduction of a flyover at the junction has to guidelines [2]. sections a large number of public transport be considered. Furthermore, an adequate The methodology adopted to identify the  Determination of the inscribed circle buses ply along with hundreds of other number of lanes should be established a teach flyover at the Rajagiriya junction was through diameter of the proposed roundabout privately owned vehicles. Buses take a approaching intersection to cater to the a highway traffic analysis using the following: considering the existing available land area considerably long time to pass Rajagiriya in expected traffic flows. and finding out the rotary carriage width moving towards Nawala and Kohilawatta. The  Identification of the existing geographical and radius of the central island. three junctions hinder the flow of traffic along and layout arrangements of the project  Selection of suitable dimensions for the the main route thereby increasing traffic 2. Aim and Objectives area. roundabout according to the geometric data congestion along the main route (i.e. Sri  Conducting a survey to identify the main and preparation of the detail drawings. Jayawardhanapura road). The aim of this study is to observe whether the commercial, school and office buildings  Obtaining the horizontal and vertical curve existing road capacities are adequate to cater to and public institutions located in the area. lengths for the flyover at a design speed of Many government offices and public the current traffic volumes and if found  Accurate identification of the locations of 72 km/h. institutions outside the Colombo city centre inadequate to design the road and buildings in the area using Google maps.  Checking head lamp visibility during night are located close to the study area resulting in intersections in such a way so as to cater to the  Identification of the road network in the time at a design speed of 72 km/has set out an increase in the traffic flow(e.g. Sethsiripaya, anticipated future traffic. This study also hopes project area using the existing road survey in the highway design capacity manual Isurupaya, Parliament etc.) to this area. to propose ways and means of improving the drawings of the Road Development 2012 [3]. Vehicles arriving at these destinations use this roads by introducing appropriate road widths Authority (RDA) and Google maps. route daily leading to an increase in the daily and a few lanes in the study area to cope up  Measurement of the existing road and 3.3 Structural Design of the Flyover traffic flow. The unavailability of dedicated with the traffic needs to provide a satisfactory shoulder widths accurately. parking lanes or slots compels the drivers to level of service. The outcome of this study is  Obtaining from the RDA, the traffic count  Piers were introduced to the flyover taking park their vehicles along the road, and this too expected to introduce a suitable solution to data of the past years at the Colombo city in to consideration the maximum span of the has contributed to the increased traffic ease the projected traffic congestion at the entry point to determine AADT and growth available beams (25m) so as to ensure congestion. Police station junction, Bo-tree junction and rates. minimum obstruction to the access roads to Kohilawatta road junction.  Conducting turning movement surveys for the Rajagiriya junction.

identified locations.  Pre-stressed concrete beams were designed

Towards fulfilling this aim, the objective of the  Checking the available pre-stressed beam using BS 5400 [4]. study would be to justify and design a solution sizes and lengths.  Piers were designed according to the for the safe movement of vehicular traffic at guidelines given in BS 5400 [4]. the Rajagiriya junction by paying attention to 3.2 Traffic Study

Kohilawatta the following: Bo-tree junction junction 1. Identification of peak hours based on (main junction)  Identification of the peak period using 4. Data and Analysis available traffic data. turning movement survey results. 2. Conduct of turning movement surveys Police station  Obtaining the Level of Service (LOS) from 4.1 Identification of the Peak Hours junction of traffic at the respective junctions the existing road section. during peak hours on week days.  Introduction of a flyover bridge to cater to The traffic flow along a road does not remain

3. Identification of the road widths and the main traffic flows. constant throughout a day or week but varies Figure 1 - Location of the Study Area the number of lanes currently  Carrying out the traffic volume forecast for with both space and time. The peak hour available to determine future the next twenty years. represents the most critical period for Traffic congestion can cause several problems requirements. such as economic costs resulting from delayed operations and has the highest capacity 2 3 35

requirements for a given location. Three peak widening, building corners and the radius of hours of the day were identified from the existing horizontal curves are indicated. traffic data collected from the RDA at fifteen minute intervals in the morning, mid-day and 4. 3 Analysis of the Traffic Flow Volume evening peaks respectively for the Police & Capacity station junction, Bo-tree junction and The US Highway Capacity Manual was used to Kohilawatta road junction. Traffic surveys calculate the LOS at each section of the existing were carried out from 6:30 am to 9:30 am, 12:00 road. In making this calculation the following pm to 3:00 pm and from 4:30 pm to 7:30 pm. basic relationships were used: Figure 2 shows the observed number of vehicles during the time periods mentioned. From Figure 2 it can be seen that the peakhour would be between 5:30pm and 6:30pm. 𝑉𝑉 ͳͷ 𝑃𝑃𝐻𝐻𝐹𝐹 ൌ  Ͷൈ𝑉𝑉 𝑉𝑉

𝑃𝑃𝐻𝐻𝐹𝐹 𝑆𝑆𝐹𝐹 ൌ  Peak hour Identified peak 𝑆𝑆𝐹𝐹𝑖𝑖  ൌ 𝐶𝐶𝑗𝑗 ൈ ሺ𝑣𝑣Ȁ𝑐𝑐ሻ𝑖𝑖 ൈ 𝑁𝑁 ൈ 𝑓𝑓𝑤𝑤 ൈ 𝑓𝑓𝐸𝐸 ൈ hour 𝐻𝐻𝑉𝑉 = 𝑝𝑝 𝑓𝑓 ൈ 𝑓𝑓 ͳ

𝐻𝐻𝑉𝑉 𝑇𝑇 𝑇𝑇 𝐵𝐵 𝐵𝐵 w𝑓𝑓 here,ሾ ͳ൅𝑃𝑃 ሺ𝐸𝐸 −ͳሻ൅𝑃𝑃 ሺ𝐸𝐸 −ͳሻሿ

- Peak hour factor

𝑃𝑃𝐻𝐻 𝐹𝐹 - Hourly volume

𝑉𝑉 - Highest 15 minute volume

ͳͷ 𝑉𝑉 - Service flow rate; the maximum flow rate in vph that can be 𝑖𝑖 𝑆𝑆𝐹𝐹 accommodated by the multilane highway segment under study, in one direction, under prevailing roadway and traffic conditions, Figure 2 – Traffic flow while meeting the performance criteria of LOSi

4.2 Detailed Survey Drawing of the - Capacity per lane for a multilane Selected Area highway with design speed 𝑗𝑗 𝐶𝐶

- Number of lanes in one direction

𝑁𝑁 - Maximum volume-to-capacity ratio while maintaining the 𝑖𝑖 ሺ𝑣𝑣Ȁ𝑐𝑐ሻ performanceCharacteristics of LOSi

- Adjustment factor for lane width and/or lateral clearance restrictions 𝑓𝑓 𝑤𝑤 - Adjustment factor for the presence of heavy vehicles in the traffic stream 𝑓𝑓 𝐻𝐻𝑉𝑉 -Adjustment factor for the

development environment and type

𝐸𝐸 of multilane highway Figure 3 – Detailed Survey Drawing 𝑓𝑓

-Adjustment factor for driver In Figure 3, dimensions such as center lines, chainages, earmarked boundaries for future population 𝑓𝑓 𝑝𝑝 4 36

requirements for a given location. Three peak widening, building corners and the radius of , - Passenger-car equivalents for trucks = 1 / (1 + 0.04 (1.7 - 1) + 0.006 (1.5 - 1)) hours of the day were identified from the existing horizontal curves are indicated. and buses = 0.97 traffic data collected from the RDA at fifteen 𝐸𝐸 𝑇𝑇 𝐸𝐸𝐵𝐵 minute intervals in the morning, mid-day and 4. 3 Analysis of the Traffic Flow Volume - Proportion of trucks and buses in the For a Design speed of 50 mph evening peaks respectively for the Police & Capacity traffic stream No of lanes = 3 𝑇𝑇 𝐵𝐵 CJ = 2000 (Table 3.1 - Highway station junction, Bo-tree junction and The US Highway Capacity Manual was used to 𝑃𝑃 ǡ 𝑃𝑃 capacity manual) Kohilawatta road junction. Traffic surveys calculate the LOS at each section of the existing 4.4 Level of Service Criteria (LOS) were carried out from 6:30 am to 9:30 am, 12:00 v/c = SF / (Cj × N × Fw× FHV × FE × FP) road. In making this calculation the following The level of service criteria for multilane and pm to 3:00 pm and from 4:30 pm to 7:30 pm. = 3275/(1900x3x0.84x0.97x0.90x1) basic relationships were used: two lane highways are defined in terms of Figure 2 shows the observed number of = 0.788 vehicle density [1]. The complete LOS criteria vehicles during the time periods mentioned. It is seen that the current LOS for this stretch is are given in the US Highway Capacity Manual From Figure 2 it can be seen that the peakhour E which is unsatisfactory. The existing road 𝑉𝑉 at the design speeds of 70mph, 60mph and would be between 5:30pm and 6:30pm. stretches where LOS is lower than D need to be ͳͷ 𝑃𝑃𝐻𝐻𝐹𝐹 ൌ  Ͷൈ𝑉𝑉 50mph. This gives the average travel speeds, 𝑉𝑉 improved. and the Maximum Service Flow (MSF)rate at 𝑃𝑃𝐻𝐻𝐹𝐹 𝑆𝑆𝐹𝐹 ൌ  each level of service. Peak hour 4.6 Traffic Volume Forecast Identified peak 𝑆𝑆𝐹𝐹𝑖𝑖  ൌ 𝐶𝐶𝑗𝑗 ൈ ሺ𝑣𝑣Ȁ𝑐𝑐ሻ𝑖𝑖 ൈ 𝑁𝑁 ൈ 𝑓𝑓𝑤𝑤 ൈ 𝑓𝑓𝐸𝐸 ൈ hour 𝐻𝐻𝑉𝑉 = 𝑝𝑝 4.5 Determination of the current LOS Using the existing traffic volumes and relevant 𝑓𝑓 ൈ 𝑓𝑓 ͳ growth factors obtained from the RDA, the The LOS was calculated for the Kollupitiya to 𝐻𝐻𝑉𝑉 ሾͳ൅𝑃𝑃𝑇𝑇 ሺ𝐸𝐸𝑇𝑇 −ͳሻ൅𝑃𝑃𝐵𝐵 ሺ𝐸𝐸𝐵𝐵 −ͳሻሿ future traffic in the study area was computed. w𝑓𝑓 here, Battaramulla direction Section 1-1 shown in This helped to foresee the traffic demand in Figure 3. The volume was calculated using the another 20 years from now. This in turn helped - Peak hour factor summation of the turning movement survey to decide the highway capacity for a suitable volumes from Kollupitiya to Battaramulla and level of service for the time period concerned. 𝑃𝑃𝐻𝐻 𝐹𝐹 - Hourly volume Kollupitiya to Nawala at the Police station

junction. 𝑉𝑉 - Highest 15 minute volume The morning peak hour flows were taken The peak hour volume during the period from towards Colombo direction and evening peak ͳͷ 𝑉𝑉 - Service flow rate; the maximum flow 5:30 pm to 6:30 pm was considered. hour flows were taken for the opposite rate in vph that can be direction. 𝑖𝑖 𝑆𝑆𝐹𝐹 accommodated by the multilane No of lanes = 3 highway segment under study, in Full hour volume = 3177vph The growth rates can be calculated as follows: one direction, under prevailing Maximum 15 min volume = 821vph Predicted traffic volume roadway and traffic conditions, Peak hour factor = = (Existing traffic volume) × (1 + g) n Figure 2 – Traffic flow while meeting the performance 3177/(4x821) = 0.97 criteria of LOSi Table 1 – Growth Rates for Passenger Cars Service flow rate = 3177 / 0.97 2010 – 2012 – 2017 – 2022 - 2027 - 4.2 Detailed Survey Drawing of the - Capacity per lane for a multilane = 3275vph 2012 2017 2022 2027 2032 Selected Area highway with design speed Distance of travelled pavement = 6ft 𝑗𝑗 5.2 4.3 4.1 3.6 2.8 𝐶𝐶 Lane width = 9.5ft

fw = 0.84 (Table - Number of lanes in one direction From Kollupitiya to Battaramulla at Police 7.2 – Highway Capacity Manual 1985) station Junction - Maximum volume-to-capacity ratio fp = 1.00 (Table 7.11 – 𝑁𝑁 while maintaining the Highway Capacity Manual 1985) 𝑖𝑖 Sample Calculation: ሺ𝑣𝑣Ȁ𝑐𝑐ሻ performanceCharacteristics of LOSi Multilane highway is divided and suburban fE = 0.90 (Table 7.10 – Existing traffic volume of passenger cars - Adjustment factor for lane width Highway Capacity Manual 1985) (6:30 am – 6:45 am) = 90 and/or lateral clearance restrictions Adjustment factor for heavy vehicles (FHV), 𝑤𝑤 𝑓𝑓 Percentage of trucks = 118 / 3177 Predicted traffic volume during the period - Adjustment factor for the presence of (PT) = 0.04 from the year 2013 to the year 2017 heavy vehicles in the traffic stream Percentage of buses = 19 / 3177 Number of years =4 𝐻𝐻𝑉𝑉 4 𝑓𝑓 (PB) = 0.006 Traffic volume in 2017 = (90) × (1+0.043) -Adjustment factor for the =106.5 Passenger car equivalent factor for trucks development environment and type Predicted traffic volume from the year 2017 to (ET) = 1.7 𝐸𝐸 of multilane highway Figure 3 – Detailed Survey Drawing 𝑓𝑓 Passenger car equivalent factor for buses 2022, Traffic volume in 2022 = 130.2 (EB) = 1.5 -Adjustment factor for driver In Figure 3, dimensions such as center lines, (Table 7.3 – Highway Capacity Manual 1985) Predicted traffic volume during the year from chainages, earmarked boundaries for future population 2022 to 2027: 𝑓𝑓 𝑝𝑝 FHV = 1 / (1 + PT (ET - 1) + PB (EB - 1)) Traffic volume in 2027 = 155.4 4 5 37

Predicted traffic volume from the year 2027to Table2 – Suitability of roundabout the year 2035, Sub- Traffic volume in 2035 =183.4 Arterial Collector Local Road arterial road road street road 4.7 Separation of the Traffic Flow Arterial B B X X To cause minimum disturbance to the traffic Sub-arterial - B B X along Sri Jayewardenepura road (the main Collector - - A B traffic flow), a flyover was proposed. Local street - - - A

4.8 Passenger Car Unit (PCU)Values Notation: In order to find out the number of lanes, it was necessary to convert the number of vehicles in A - Likely to be an appropriate treatment to PCU. This was done using PCU equivalency B - May be an appropriate treatment. factor. Each category of vehicle has a different X - Inappropriate treatment. PCU value. 5.2 Turning Movement Data 4.9 Capacity Analysis for the Flyover for a period of 20 years FromRajagiriya

The number of lanes was found out for the 888 583 flyover using the Highway Capacity Manual 269 1985. To Kollupitiya To Battaramulla

Full hour volume = 3955 vph

Full hour volume = 3595 pcu 921 Maximum 15 min volume = 1069 vph 388 386 Peak hour factor = 3955/(4x1069) 471 = 0.92 333 Service flow rate = 3595/0.92 From Nawala = 3907pcuph Lane width =12ft fw =0.97 Figure 4 – Turning movement diagram (veh/h) fp = 1.00 fE = 1.00

PT =0.063

PB =0.009 FromRajagiriya (ET) =1.7

(EB) = 1.5 1307 1740

FHV = 1/(1 + PT (ET - 1) + PB (EB - 1))

= 1/(1 + 0.063 (1.7 - 1) + 0.009 (1.5 - 1))

= 0.95 v/c = 1.00 To Kollupitiya 859

N = SF / (Cj × v/c × Fw× FHV × FE × FP) 1780 971 =2.94 => 3 386 1628 To Battaramulla

Therefore, three lanes in each direction would 269 719 be required. 655

From Nawala 5. Roundabout Design

1692 5.1 Suitability of Roundabout Design

The basic criteria adopted by AUSTROAD to Figure 5 – Roundabout entry, exit and decide on the suitability of a roundabout are circulating flows (veh/h) at the Bo tree indicated in Table 2. junction

6 38

Predicted traffic volume from the year 2027to Table2 – Suitability of roundabout 5.3 Gap Acceptance Analysis the year 2035, The geometric design is very important in a Sub- The gap acceptance parameters are affected by Traffic volume in 2035 =183.4 Arterial Collector Local roundabout design since the vehicles have to Road arterial the geometry of the entry. At higher circulating road road street pass the roundabout easily free from accidents. road flows, the circulating speeds would be lower. 4.7 Separation of the Traffic Flow Arterial B B X X To cause minimum disturbance to the traffic Sub-arterial - B B X As per AUSTROADS [2] for a multi-lane along Sri Jayewardenepura road (the main Collector - - A B roundabout, traffic flow), a flyover was proposed. Local street - - - A Critical acceptance gap =T =4 sec

Follow-up headway =TC = 2 sec 4.8 Passenger Car Unit (PCU)Values Notation: Minimum headway =tc = 0 sec In order to find out the number of lanes, it was necessary to convert the number of vehicles in A - Likely to be an appropriate treatment 5.4 Capacity of the Entry Lanes to PCU. This was done using PCU equivalency B - May be an appropriate treatment. Entry and circulating flows based on the turning factor. Each category of vehicle has a different X - Inappropriate treatment. movement data are presented in Figures 5&6. It PCU value. was necessary to find out the entry capacity of

5.2 Turning Movement Data the roundabout. The traffic flow from the 4.9 Capacity Analysis for the Flyover for directions of Rajagiriya and Kollupitiya are high a period of 20 years FromRajagiriya when compared to that which comes from the

Figure 7 – Sight Triangle The number of lanes was found out for the Battaramulla direction. There is no entry flow 888 583

269 flyover using the Highway Capacity Manual from the Nawala direction, although there is an 1985. exit flow in that direction. 5.7 Central Island and Circulating To Kollupitiya To Battaramulla Carriageway Width Full hour volume = 3955 vph From Rajagiriya The design speed as the roundabout is Full hour volume = 3595 pcu 921 approached is 40 km/h. The minimum central Maximum 15 min volume = 1069 vph 388 386 1740 island diameter is 15 m and the circulating Peak hour factor = 3955/(4x1069) 471 carriageway width is 11.1 m. = 0.92 333

Service flow rate = 3595/0.92 859 From Nawala 5.8 Inscribed Diameter = 3907pcuph 1780 To Lane width =12ft Battaramulla The roundabout is to be located at the To 386 1628 fw =0.97 centerline of the intersection of roads and the Figure 4 – Turning movement diagram (veh/h) Kollupitiya 386 fp = 1.00 719 inscribed diameter was found to be 37.2 m. fE = 1.00 655 According to the detailed survey drawing, an

PT =0.063 655 inscribed diameter of 37.2 meters was found to

PB =0.009 00 be adequate. FromRajagiriya (ET) =1.7 From Nawala (EB) = 1.5 1307 1740

FHV = 1/(1 + PT (ET - 1) + PB (EB - 1)) Table 3 – Details of Roundabout Flows Figure 6 – Roundabout entry, exit and = 1/(1 + 0.063 (1.7 - 1) + 0.009 (1.5 - 1)) circulating flow (pcu/h) at the Bo tree junction = 0.95 Forecast To Kollupitiya 859 traffic Maximu Average v/c = 1.00 Circulating Traffic flow volume m entry queuing N = SF / (Cj × v/c × Fw× FHV × FE × FP) flow 1780 971 5.5 Queuing Delay direction of entry capacity delay =2.94 => 3 386 1628 To Battaramulla (vph) The average queuing delay was found using lanes (vph) (sec) the graph obtained by plotting the average (vph) Therefore, three lanes in each direction would 269 719 queuing delay against the circulating flow. The From be required. 655 1780 386 2592 7 maximum delay is 50 seconds and none of the Kollupitiya queuing values exceeds this maximum delay. From From Therefore the given queuing values would be 1740 859 1960 41 Nawala Rajagiriya 5. Roundabout Design acceptable.

1692 From 5.1 Suitability of Roundabout Design 719 1628 940 24 5.6 Sight Triangle & Geometric Design of Battaramulla The basic criteria adopted by AUSTROAD to Figure 5 – Roundabout entry, exit and the Roundabout From 00 655 2100 0 circulating flows (veh/h) at the Bo tree Nawala decide on the suitability of a roundabout are For the drivers to have a clear view of the junction indicated in Table 2. approaching traffic there has to be an area of

sight unobstructed by buildings or other

obstacles at the corners of an intersection. 6 7 39

5.9 Corner Radii (R3) Table 4 – Details of Corner Cut-off Corner radii are functions of the inscribed Direction Corner Cut-off circle radius and the approach and departure (C) carriage way width. When two roads intersect Nawala and Kollupitiya 8.42 m the roads have to have equal width. For the Kollupitiya and Rajagiriya 3.54 m special case where the intersecting roads are of Rajagiriya and Battaramulla 2.16 m equal width W, this expression simplifies to: Battaramulla and Nawala 1.60 m

R3 = R1 – 2 W + where, 5.11 Minimum Possible Lateral Deflection into the Intersecting Street (Z) R3 - Corner radii ʹሺ𝑅𝑅ͳ − 𝑊𝑊ሻ R1 -Inscribed radius = 18.6 m The deflection Z into the cross street is given W - Width between carriageway by, centreline and kerb on the adjacent Z = R1 – W2 + z approach and departure respectively where, = 7.2 m W2 - Approach width R3 = R1 – 2 W + √ 2(R1 - W) z - Width of vehicle path = 2.4 m = 9 m Z = R1– W2 + z Z =13.8 m 5.10 Corner Cut-off The property boundaries at the corners of the 5.12 Maximum Speed of a Vehicle through intersection have to be truncated. The amount the Roundabout of truncation will be a function of the corner The circulation of vehicle accident rate on any kerb radius, the footway width and the particular approach is largely related to the intersection angle. relative potential speeds of the entering and circulating vehicles. A decrease in speed will The formula is C = provide a number of reverse curves to the 𝑅𝑅͵−𝑊𝑊Ͷ entry curve to limit the maximum decrease in where, 𝜃𝜃 speed between the horizontal geometric –ƒ ʹ elements. R3 - the kerb radius W4 - the footway width The maximum speed of a vehicle through a θ - angle between intersecting street roundabout can be calculated by,

Rajagiriya V =

where, V - Vehicle ሼͳʹ͹ speed𝑅𝑅Ͷሺ 𝑒𝑒(km/h) ൅ 𝑓𝑓ሻ

R4 - Maximum path radius (m) e - Super elevation (m/m) [negative if the fall is from the central island] f - Allowable coefficient of friction (sideway friction between vehicle tyres 0 0 80.53 108.36 Battaramulla and road pavement)

Assuming that there is no super elevation ------within the roundabout Kollupitiya 0 0 e =0, f = 0.2 39.2 123.8 V = = 39.68 km/h

Ͷ 5.13 Splitter ሼͳʹ͹ Island𝑅𝑅 ሺ𝑒𝑒  ൅ 𝑓𝑓ሻ

This is mostly used to decrease the speed at the

------start of the entry curve when speeds are high. Nawala Here the entry curve radius is 85 m. The exit

curve is 136 m. The 0.3 m offset provides for Figure 8 – Intersecting angle of street the splitter island. The corner radius of the

splitter island is 0.75 m and it has a 0.2 m thick concrete kerb. 8 40

5.9 Corner Radii (R3) Table 4 – Details of Corner Cut-off Total tangent length = (R + S) tan (∆/2) + (L/2) Corner radii are functions of the inscribed Direction Corner Cut-off circle radius and the approach and departure (C) L - Length of transition curve carriage way width. When two roads intersect Nawala and Kollupitiya 8.42 m R - Radius of curve the roads have to have equal width. For the Kollupitiya and Rajagiriya 3.54 m ∆ - Deflection angle of the straights special case where the intersecting roads are of Rajagiriya and Battaramulla 2.16 m equal width W, this expression simplifies to: Battaramulla and Nawala 1.60 m Total tangent length

Figure 9 – Splitter island = (203 + 1.748) tan (580 41‟ 24”/2) + (92.295 / 2) R3 = R1 – 2 W + = 161.258 m where, 5.11 Minimum Possible Lateral Deflection Angle of the circular curve = ∆ - 2φ into the Intersecting Street (Z) R3 - Corner radii ʹሺ𝑅𝑅ͳ − 𝑊𝑊ሻ 6. Horizontal and Vertical = 320 38‟ 24” R1 -Inscribed radius = 18.6 m The deflection Z into the cross street is given Alignment Length of the circular curve (T1”T2”) W - Width between carriageway by, = [πR (∆ - 2φ)] / 1800 0 0 centreline and kerb on the adjacent Z = R1 – W2 + z 6.1 Horizontal Alignment of the Flyover = (π × 203 × 32 38‟ 24‟‟) / 180 approach and departure respectively where, = 115.644 m The horizontal alignment of the flyover is = 7.2 m W2 - Approach width along the tangent and the curve has been R3 = R1 – 2 W + √ 2(R1 - W) z - Width of vehicle path = 2.4 m Chainage of A = 1268.477 m designed to discourage operating speeds = 9 m Z = R1– W2 + z Chainage of point T1‟ = 1268.477 - 161.258 higher than 72 km/h. Although the existing Z =13.8 m = 1107.219 m curve 01 has been designed for 55 km/h it is 5.10 Corner Cut-off Chainage of T2‟ = Chainage of T1‟ + 2 × found to be not sufficient. It has to be noted 5.12 Maximum Speed of a Vehicle through transition curve length + Curve length The property boundaries at the corners of the that Sri Jayewardenepura road is heavily used the Roundabout = 1107.219 + 115.644 + 2 × 92.295 intersection have to be truncated. The amount by the Members of Parliament (MPs) as well as = 1407.253 m of truncation will be a function of the corner The circulation of vehicle accident rate on any by Very Important Persons (VIPs). kerb radius, the footway width and the particular approach is largely related to the intersection angle. relative potential speeds of the entering and V = 17.78 ms-1, x = 5cms-1, C = 0.3 m/sec2 Table 5 – Horizontal Alignment circulating vehicles. A decrease in speed will “h” is the amount of super elevation in provide a number of reverse curves to the centimetres. The formula is C = Description Curve 01 Curve 02 𝑅𝑅͵−𝑊𝑊Ͷ entry curve to limit the maximum decrease in “x” is the time rate. (= 5 cms-1) 𝜃𝜃 e 6 % 6 % where, speed between the horizontal geometric “V” - Average speed of the vehicles in –ƒ ʹ H 22 cm 20 cm elements. meters/sec x 5 cms-1 5 cms-1 R3 - the kerb radius “C” - Rate of development of radial V 17.78 17.78 W4 - the footway width The maximum speed of a vehicle through a acceleration. θ - angle between intersecting street roundabout can be calculated by, R 203 m 303 m 78.232 m 71.582 Length of transition curve (L), L1= Rajagiriya V = 𝒉𝒉 𝑽𝑽 where, L1 = 92.295 61.583 Ͷ L2= 𝒙𝒙 V - Vehicle ሼͳʹ͹ speed𝑅𝑅 ሺ 𝑒𝑒(km/h) ൅ 𝑓𝑓ሻ ℎ𝑉𝑉 𝟑𝟑 = 78.232 m 𝑽𝑽 R4 - Maximum path radius (m) 𝑥𝑥 Shift (S) 1.748 m 0.705 𝑹𝑹𝑪𝑪 e - Super elevation (m/m) [negative if Considering vertical acceleration Transition angle (φ) 0.227 rad 0.118 rad the fall is from the central island] 130 1‟ 30‟‟ 60 46‟ 5‟‟ Length of transition curve (L) = f - Allowable coefficient of friction ͵ Total Length 161.258 m 131.170 m 𝑉𝑉 0 0 (sideway friction between vehicle tyres L2 = 92.295 m Angle of circular 32 38‟ 24‟‟ 21 20‟ 2‟‟ 0 108.360 80.53 Battaramulla and road pavement) 𝑅𝑅𝐶𝐶 curve= ∆ - 2φ

Assuming that there is no super elevation Therefore the length of transition curve Length of circular ------within the roundabout = 92.295 m curve 115.644 m 112.821 m Kollupitiya 39.20 123.80 e =0, f = 0.2 = [πR(∆-2φ)]/1800 Shift (S) = ʹ V = = 39.68 km/h 𝐿𝐿 Chainage A 1268.477 m 1492.885 = ʹͶ𝑅𝑅 ʹ m Ͷ ͻʹǤʹͻͷ 5.13 Splitter ሼͳʹ͹ Island𝑅𝑅 ሺ𝑒𝑒  ൅ 𝑓𝑓ሻ = 1.748 m Chainage of point 1107.219 m 1361.715 ሺʹͶൈʹͲ͵ሻ This is mostly used to decrease the speed at the T1‟ m

------start of the entry curve when speeds are high. Chainage of T2‟ 1407.253 m 1617.7 m Nawala Angle consumed by each transition (φ) = Here the entry curve radius is 85 m. The exit 𝐿𝐿 curve is 136 m. The 0.3 m offset provides for = The horizontal alignment of the flyover is Figure 8 – Intersecting angle of street ʹ𝑅𝑅 the splitter island. The corner radius of the ͻʹǤʹͻͷ shown in Figure A4 of Appendix A. = 0.227 rad = 130 1‟ 30” ሺʹൈʹͲ͵ሻ splitter island is 0.75 m and it has a 0.2 m thick

concrete kerb. 8 9 41

6.2 Vertical Alignment of the Flyover 6.4 Sag curve of Vertical Alignment The vertical alignment is the combination of parabolic vertical curves and the straight sections joining them. The straight sections are referred to as grades, and the values of their slope are the gradients, usually expressed as a percentage. The design speed applied to the Figure 11 – Sag curve alignment vertical alignment should therefore match that applied to the horizontal alignment. A = g1% - g2% = 5% - (0%) = 5% 6.3 Crest Curve of Vertical Alignment Chainage of A2 = 66.67 m Chainage of T1 = 200 m Reduced level of T1 = 108 m Reduced level of T2 = 100 m Equation of grade line, Y = mx + c, Y = 0x + 100 Y = 100 Consider a design speed of 45 mph and a Figure 10 – Crest curve grade +5% then stopping sight distance is

331.67 ft (101 m) (Design manual capacity 2003, Determination of stopping sight distance: figure 7-1A) Design speed = 45 mph (72 kmph) To find the headlamp visibility, two possible

scenarios are considered. Grades, S ≤ L and S ≥ L. g1 = +5% Make an angle of +20 with the horizontal. g2 = -5% Headlamp position 650 mm above the road A = g1% - g2% surface. = 5% - (-5%) = 10% For S ≤ L, Stopping sight distance is minimum for the L = S2A / 200 (h + S tanα) vertical crest curve. The height of the eye was where, considered as 3.5 ft (1.07 m) on the road S =101 m surface and the height of object as 2 ft (0.61 m). H = 0.65 m Chainage of T1 = 1200 m Α = +20 Reduced level of T1 = 108 m So, Equation of grade line, L = (1012 × 5) / 200 (0.65 + 101 × tan 20) Y = mx + C L ` = 61 m Y = 0.05x + 108 Therefore, this value is not valid. L = AS2 / [200 ( + )2] For S ≥ L, where, L = 2S – 200 (h + S tan α) /A h1= 1.07 m h2 = 0.61m Šͳ ℎʹ L = 2×101– 200 (0.65 + 101× tan 20) /5 A = 10% L = 35 m < 101 m Stop sight distance for (5%) = 393 ft = 120 m This value is valid. L = 10 × 1202/ [200 ( + )2] Therefore sag curve length is 35 m. = 218.5 m < 225 m The equation of a parabolic curve is given by, The equation of a parabolic ͳ curveǤͲ͹ isͲ givenǤ͸ͳ by, Y = ax2 + bx + c Y = ax2 + bx + c It‟s gradient at a point, It‟s gradient at a point, = 2ax + b = 2ax + b Rate of change𝑑𝑑𝑦𝑦 of gradient along the curve, 𝑑𝑑𝑦𝑦 𝑑𝑑𝑥𝑥 Rate of change of gradient along the curve, = 2a (a constant) 𝑑𝑑𝑥𝑥 ʹ = 2a (a constant) 𝑑𝑑 𝑦𝑦 ʹ Mid off setʹ (Y) = AL / 800 𝑑𝑑 𝑥𝑥 𝑑𝑑𝑥𝑥 = (10 × 35) / 800 Midʹ -off set (Y) = AL / 800 𝑑𝑑𝑥𝑥 = (10 × 225) / 800= 2.813 m = 0.438 m Off set (y) = X2A / 200A Off set (y) = X2A / 200 L = 10x2 / 200 × 225= x2/ 4500 = 5X2 / 200 × 35 = X2 / 1400 10 42

6.2 Vertical Alignment of the Flyover 6.4 Sag curve of Vertical Alignment Chainage of A = 1200 - (8 / 0.05) safety when transporting passengers and goods = 1040 m by road. The vertical alignment is the combination of Chainage of T2 = 1040 - (35 / 2) parabolic vertical curves and the straight = 1022.5 m At the edge of the flyover, there has to be a sections joining them. The straight sections are Chainage of T1 = 1040 + (35 / 2) barrier. Barriers ensure safety of vehicles referred to as grades, and the values of their = 1057.5 m travelling below the flyover. Barriers can be slope are the gradients, usually expressed as a made of steel, pre-stressed and in-situ concrete. percentage. The design speed applied to the Figure 11 – Sag curve alignment The vertical alignment details of the flyover are For flyovers and barriers pre-stressed concrete vertical alignment should therefore match that shown in Figure A5 of Appendix A. and steel are widely used. applied to the horizontal alignment. A = g1% - g2%

= 5% - (0%) = 5% 6.5 Details of the Flyover 7.5 Details of the Deck and the Beam of 6.3 Crest Curve of Vertical Alignment Chainage of A2 = 66.67 m the Flyover Chainage of T1 = 200 m Chainage at the beginning of the flyover Reduced level of T1 = 108 m = 1022.5 m Details of the deck Reduced level of T2 = 100 m Chainage at the end of the flyover Width of a lane = 3.66 m Equation of grade line, = 1603.0 Number of lanes = 6 Nos Y = mx + c, Overall length of the flyover Width of the carriageway = 22 m Y = 0x + 100 = 1603.0 – 1022.5 Median width = 0.8 m Y = 100 = 580.5 m Shoulder width = 0.3 × 4 Consider a design speed of 45 mph and a = 1.2 m Figure 10 – Crest curve grade +5% then stopping sight distance is Length of the flyover = 580.5 m Therefore,

331.67 ft (101 m) (Design manual capacity 2003, Total width of flyover = 24 m Determination of stopping sight distance: figure 7-1A) Width of the flyover Details of beam Design speed = 45 mph (72 kmph) To find the headlamp visibility, two possible = Carriageway width + (Width of Overall length of a beam = 32 m scenarios are considered. clearance × 4) + median width Length of a beam = 32 – (2×0.04) Grades, S ≤ L and S ≥ L. = (3.66 × 6) + (0.3 × 4) + 0.8 = 31.92 m g1 = +5% Make an angle of +20 with the horizontal. = 24 m g2 = -5% Headlamp position 650 mm above the road A = g1% - g2% surface. 8. Conclusion = 5% - (-5%) = 10% For S ≤ L, 7. Structural Design of the Flyover Stopping sight distance is minimum for the L = S2A / 200 (h + S tanα) The design of the flyover was done for the vertical crest curve. The height of the eye was where, 7.1 Details of the Beam Section projected traffic of the year 2035 and the considered as 3.5 ft (1.07 m) on the road S =101 m flyover was located in such a way so as to surface and the height of object as 2 ft (0.61 m). Pre-stressed „I‟ section beams were selected for H = 0.65 m avoid becoming a hindrance to the three Chainage of T1 = 1200 m the flyover. The maximum span was at the bay Α = +20 junctions. The location of the flyover was Reduced level of T1 = 108 m above the roundabout. The design was done So, decided based on the prevailing operating Equation of grade line, according to BS 5400:1978 Part 02, BS 5400:1978 L = (1012 × 5) / 200 (0.65 + 101 × tan 20) conditions. Pre-stressed material was proposed Y = mx + C Part 04 and BS8110:1997 codes [4], [5], [6]. L ` = 61 m for the flyover considering economic reasons Y = 0.05x + 108 Therefore, this value is not valid. 7.2 Details of the Cantilever Beam with pre-stressed concrete, and in-situ concrete L = AS2 / [200 ( + )2] For S ≥ L, proposed for beams and piers respectively. where, L = 2S – 200 (h + S tan α) /A Grade 40 concrete was used for the cantilever h1= 1.07 m h2 = 0.61m Šͳ ℎʹ L = 2×101– 200 (0.65 + 101× tan 20) /5 beam. The cantilever beam design was done Roundabouts were found to be suitable in A = 10% L = 35 m < 101 m according to the required dimensions. BS codes managing traffic flow under the flyover. The Stop sight distance for (5%) = 393 ft = 120 m This value is valid. [4] & [5] were used for the cantilever beam design of the roundabout was done based on L = 10 × 1202/ [200 ( + )2] Therefore sag curve length is 35 m. design. Australian Standards and using turning = 218.5 m < 225 m The equation of a parabolic curve is given by, templates. The selection and design of a The equation of a parabolic ͳ curveǤͲ͹ isͲ givenǤ͸ͳ by, Y = ax2 + bx + c 7.3 Details of the Piers roundabout, as with any intersection, requires Y = ax2 + bx + c It‟s gradient at a point, Piers were designed using BS 5400 [5]. the balancing of competing objectives. These range from transportation related factors like It‟s gradient at a point, = 2ax + b Rectangular reinforced concrete columns of safety, operational performance, and = 2ax + b 𝑑𝑑𝑦𝑦 grade 40 concrete were used for the piers. Rate of change of gradient along the curve, accessibility for all users and other factors such 𝑑𝑑𝑦𝑦 𝑑𝑑𝑥𝑥 Cross-sections of 3m × 1m rectangular piers Rate of change of gradient along the curve, as land use, aesthetics, and environment. 𝑑𝑑𝑥𝑥 = 2a (a constant) were used to support the flyover deck. ʹ Flexible concepts should allow room for = 2a (a constant) Mid off set𝑑𝑑 𝑦𝑦 (Y) = AL / 800 ʹ ʹ independent designs and techniques used 𝑑𝑑 𝑥𝑥 𝑑𝑑𝑥𝑥 = (10 × 35) / 800 7.4 Safety on the Flyover Midʹ -off set (Y) = AL / 800 should cater to particular situations while 𝑑𝑑𝑥𝑥 = 0.438 m = (10 × 225) / 800= 2.813 m The flyover has to be designed in such a way ensuring performance based evaluation of 2 Off set (y) = X2A / 200 L Off set (y) = X A / 200A that there is the highest possible degree of those designs. Finally a suitable layout plan 2 2 = 5X2 / 200 × 35 = 10x / 200 × 225= x / 4500 was introduced for the study. The design of = X2 / 1400 10 11 43

the flyover will mostly dependent on land Chapters 1-9, Virginia Transportation acquisition and cost. Training Academy [4]. BS 5400 (1978), Part 2, Structural use of Concrete, British Standards Institution. References [5]. BS 5400 (1978), Part 4, Structural use of Concrete, British Standards Institution [1]. Highway Capacity Manual (2000), Special [6]. BS 8110 (1997), Part 1, Structural Design Report 209, Transportation Research with Reinforced Concrete, British Standards Board, National Research Council, Institution. Washington, D. C. [2]. AUSTROADS (1991), Guide to Traffic Engineering practice, Part 6, ‘Roundabouts’, AUSTROAD Publications, NSW, Australia. [3]. Joe Hummer, Raleigh, N. C. (2012) „2010 Highway Capacity Manual‟ Day 1, Unit 1,

12 44 the flyover will mostly dependent on land Chapters 1-9, Virginia Transportation Appendix A acquisition and cost. Training Academy [4]. BS 5400 (1978), Part 2, Structural use of Concrete, British Standards Institution. References [5]. BS 5400 (1978), Part 4, Structural use of Concrete, British Standards Institution [1]. Highway Capacity Manual (2000), Special [6]. BS 8110 (1997), Part 1, Structural Design Report 209, Transportation Research with Reinforced Concrete, British Standards Board, National Research Council, Institution. Washington, D. C. [2]. AUSTROADS (1991), Guide to Traffic Engineering practice, Part 6, ‘Roundabouts’, AUSTROAD Publications, NSW, Australia. [3]. Joe Hummer, Raleigh, N. C. (2012) „2010 Highway Capacity Manual‟ Day 1, Unit 1,

Appendix A – Figure A1 – Existing drawing at Rajagiriya junction

Appendix A –Figure A2 – Underneath of the Flyover

12 13 45

Appendix A –Figure A3 – Longitudinal Section of the Flyover

Appendix A –Figure A4 – Flyover Vertical Alignment Details

Appendix A –Figure A5 – Flyover Horizontal Alignment Details

14 46

Appendix A –Figure A3 – Longitudinal Section of the Flyover

Appendix A –Figure A6 – Turning Movements Roundabout at the Bo tree junction

Appendix A –Figure A4 – Flyover Vertical Alignment Details

Appendix A –Figure A7 – Land Acquisition Drawing at the Rajagiriya junction

Appendix A –Figure A5 – Flyover Horizontal Alignment Details

14 15 47