Treatment of Junctions- Volume I: Final Report
Treatment of Junctions
FINAL REPORT Volume I Section B3: Stafford Avenue
Transportation Research and Study Centre
University of Moratuwa
Sri Lanka
15 th January 2010
Treatment of Junctions- Volume I: Final Report
Treatment of Junctions- Volume I: Final Report
Table of Contents
CHAPTER 1 INTRODUCTION ...... 1-1
1.1 Study Area ...... 1-2
1.2. Scope ...... 1-7
1.2 Data Collection ...... 1-8
CHAPTER 2 TRAFFIC ANALYSIS ...... 2-1
2.1 Traffic Movements ...... 2-1
2.2 Pedestrian Movements ...... 2-7
2.3 Speed and delay ...... 2-8
2.4 Accident Studies ...... 2-13
2.5 Road Infrastructure ...... 2-13
2.5.1 Highway Geometry of the Study Area ...... 2-14
2.5.2 Delay due to Existing Traffic Signals and Lane Geometry ...... 2-15
2.6 Summary of Observations ...... 2-16
CHAPTER 3 SOLUTIONS ...... 3-1
3.1 Localized Solutions ...... 3-1
3.1.1 Widening of Bridge and Improvements to Signalized Junction ...... 3-1
3.2 Area Wide Solutions ...... 3-3
3.2.1 Widening of Pamankada Bridge ...... 3-3
3.2.2 Improvement to Pamankada Junction ...... 3-4
3.3 Network Improvement Solutions ...... 3-5
CHAPTER 4 ECONOMIC ANALYSIS ...... 4-1
4.1 Costs ...... 4-1
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4.2 Benefits ...... 4-1
4.2.1 Traffic Analysis...... 4-1
4.2.2 Economic Benefits ...... 4-3
4.3 Cost-Benefit Analysis ...... 4-5
4.3.1 Signalization & Improvement Option ...... 4-5
CHAPTER 5 CONCLUSIONS ...... 5-1
CHAPTER 6 RECOMMENDATION ...... 6-1
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List of Tables
Table 1-1: Details of Surveys Carried Out ______1-8
Table 2-1: ADT at Stafford Avenue/A4 Junction ______2-1
Table 2-2: Flows on Links ______2-1
Table 2-3 : Hourly Pedestrian Flow ______2-7
Table 2-4: Summary of Link Travel Time (seconds) ______2-8
Table 2-5: Summary of Link Speed (km/hr) ______2-9
Table 2-6: Average Travel Speed at High Level Road ______2-11
Table 2-7: Average Travel Speed at Other Road Links ______2-12
Table 2-8 : Accident Statistics in the Study Area ______2-13
Table 2-9: The cross sectional details of the road links in the study area ______2-14
Table 2-10: Present Delay at the Signal at Stafford Avenue/A4 Junction ______2-16
Table 4-1: Cost Estimates of the Improvements ______4-2
Table 4-2: Computation of Improved Speeds and Time Savings ______4-3
Table 4-3: Economic Analysis for Signalization & Improvement Option ______4-4
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Table of Figures
Figure 1-1 : Location Map ______1-4
Figure 2-1: Hourly Traffic Flow by Vehicle Type ______2-2
Figure 2-2 : Hourly Traffic Flow by Movement ______2-2
Figure 2-3 : Hourly Link Flow ______2-3
Figure 2-4: Traffic Flow Diagrams (ADT by major vehicle groups) ______2-6
Figure 2-5: Average Hourly Pedestrian Movements at Junction ______2-8
Figure 2-6: Locations and Road Sections for Travel Time Survey ______2-10
Figure 2-7: Road Link and Lane configuration of Stafford Avenue Junction ______2-14
Figure 2-8: Calculated variation of Signal Timing during the day at Stafford Road Junctions with Existing Layout ______2-15
Figure 3-1: Improvements to junction and widening of the Bridge on A4 ______3-2
Figure 3-2: Calculated variation of Signal Timing during the day at Stafford Road Junction with Improved Layout (Blink 2005) ______3-3
Figure 3-3: Proposed Improvements to Pamankada Road and Pamankada Bridge ______3-4
Figure 3-4: Proposed Improvements to Pamankada Road and Pamankada Bridge ______3-5
Figure 6-1: Map of Study Area showing recommended improvements ______6-2
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
CHAPTER 1 INTRODUCTION
Stafford Avenue Junction is located between the 4th and 5 th km post on the Colombo-Ratnapura (A4) Road around 150 metres from the Kirulapone Town centre. This junction is signalized at the moment and is located almost on the banks of the Kirulapone Canal. The Colombo-Ratnapura (A4) Road is one of the major arteries to the Colombo City bringing both provincial traffic as well as commuter traffic to the city. Traffic from Eastern, Uva, Sabaragamuwa, Central and even Southern Province use this road as one of the primary access routes to Colombo.
A bridge across the Kirulapone canal is seen on the southern approach of the Colombo-Ratnapura (A4) Road to the junction. The Base Line Road and Colombo-Ratnapura (A4) Road junction is only 240 meters due south from the Stafford Junction. Stafford Avenue itself runs parallel to the Kirulapone Canal as shown in Figure 1.1. The less trafficked Pamankada Road also connects to the same junction from the northern direction. Its entry and exit to and from the junction are separated by a tract of land on which there is a Bo Tree and Buddha Statue. The traffic entering the junction from Pamankada Road has to enter the A4 around 65 metres to the north of the Stafford Avenue Junction. There are multi storey commercial buildings along the Colombo-Ratnapura (A4) Road in close proximity to the junction. Widening of the junction to accommodate more lanes is restricted.
The Colombo-Ratnapura (A4) Road which is the major road at this junction, has divided 4 to 5 lanes, while Stafford Avenue has undivided two lane configuration. Presently the Colombo-Ratnapura (A4) Road has two lanes in the northbound direction and three lanes in the southbound direction at the junction. The Colombo-Ratnapura (A4) Road has six lanes on both approaches away from the junction on the bridge. Therefore even without the junction there is a bottleneck on the Colombo- Ratnapura (A4) Road at this point.
The junction is congested many times during the day with long queues seen on all approaches during peak hours. It seems that the present signalization itself cannot solve the capacity problem at this junction
The Stafford Avenue is also part of a part-time one way arrangement during the morning peak from 7 am to 9 am. During this time vehicles travelling from Havelock Road to Pamankada Bridge are diverted through Stafford Avenue since the section of Dutugemunu Street between Pamankada Bridge and Havelock Road is made one way towards Colombo. This too contributes towards the am peak congestion at the Stafford Avenue/A4 junction.
The scope of the study covered in this report examines the possible short term and long term cost effective solutions to the traffic congestion within the specified study area defined as follows.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
1.1 Study Area
The traffic congestion problems at Stafford Avenue Junction seem to be primarily to the lack of capacity on the Colombo-Ratnapura (A4) Road and the impact of traffic turning in and out from Stafford Avenue especially during the peak hours. Even though the study area is localized to the junction itself, there is a need to consider some of the alternative routes that can be considered to ease the traffic congestion at this junction as well as to improve the overall traffic flow of the area.
Therefore the road network including all the intersections within a distance of 500 meters from the Stafford Junction has been considered to be within the study area (Figure 1.2). The condition of roads and traffic in the study area is given in Figure 1.3. This area includes:
1. The Pamankada Road connects the Stafford Avenue junction with Pamankada junction. However Pamankada Road cannot be used as an alternative to Stafford Avenue since the travel distance to Pamankada Bridge via Pamankada Road is much higher. Moreover, Pamankada Junction is extremely congested as the road widening project of Havelock Road has not been completed at this junction.
2. Havelock Road which connects Pamankada Junction to Dutugemunu Street is also an important connection for a possible diversion of right turning traffic from Maya Avenue to Stafford Avenue.
3. Robert Gunawardena Mawatha which is intended to be improved as the extension of Baseline Road (Phase III) can also be used to reduce turning traffic at Stafford Rd/A4 junction as well as at the Baseline Rd/A4 junction. This development will ease traffic coming along Baseline Road which is intended to go to destinations on Horana Road (B84) as well as Galle Road (A2).
The Kirulapone Canal is also a very important feature in this study area as it affects both the possible widening of the Stafford Avenue/A4 junction as well as Stafford Avenue itself.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Figure 1-1 : Location Map
Figure 1-2: Site map of the study area
Stafford Avenue Junction Long queues on Nugegoda approach on A4 at Signal Junction
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Trucks waiting for Right Turn from Stafford Avenue Orientation and location of the Bo Tree at the Junction
Land use, north of the Junction on A4 Stafford Avenue Approach at the Junction
Buildings in front of Stafford Avenue at Junction Pedestrian Sidewalk width at Junction
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Right t urn ban from Pamankada Road to High -level Road Narrow width of Pamankada Road
Parking and Commercial Activities Congesting the A4 approach from Colombo to Baseline Intersection Pamankada Road exit to A4
A4 passing Kirulapone Town Centre Bus halt on A4 towards Nugegoda passing the Stafford Junction
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Pamankada Bridge Parking Control on Stafford Avenue
Figure 1-3: Typical Road Conditions in the Study Area
1.2. Scope
The scope of work reported herein as agreed upon with the Road Development Authority, include the following:
• Analysis of Turning Movement Counts, Pedestrian Counts, Traffic Delay Counts or a full traffic survey of the local area as the case may be, in order to obtain a clear picture of the cause of the traffic congestion and to identify the remedies.
• Comprehensive analysis of traffic patterns including movement of pedestrians, parking bus circulating, in and out of bus stands and bus halting.
• Analysis of traffic accidents in the study area.
• Consider the influence of other problems such as heavy inflows, out flows of traffic from and to adjacent by-roads, misuse of road space etc.
• Identify the problems in the existing set up such as erroneous road markings, signs, signal lights with faulty phases, lack of capacity for turning circles, inadequate lane widths etc.
• Calculation of benefits for technically feasible alternatives.
• Calculation of economic benefits for the above alternatives
• Based on above, recommend suitable solutions for each location which will include, solutions such as new or improvements to signals, roundabouts, flyovers, over passes, by passes, traffic management schemes, etc.
• If over passes/ flyovers required conceptual design of them with appropriate dimensions, required legs etc.
• Report on the impact on Urban architecture
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1.2 Data Collection
The Table 1-1 shows the details of survey locations and type of surveys carried out pertaining to this study. The surveys were carried out using a pool of around 20 university students who were specifically trained and worked in groups under an experienced survey supervisor. The details of how the surveys were carried out will be given in the Appendix..
Table 1-1: Details of Surveys Carried Out
Survey Date Locations
From Saranankara Road /Havelock Road (B084) junction ‰ Stafford Avenue ‰ Stafford Avenue/High Level Road(A4) ‰ Travel Time Survey High Level / Pamankada Rd. junction ‰ Pamankada/B084 Road Junction 6 Aug Turning Movement Counts TM10 : Stafford Avenue/High Level Road Junction 2008 Near pedestrian crossings and along the roads in the vicinity of Pedestrian Counts the junction
Queue Length Survey On the three arms of the Stafford Avenue/A4 junction
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
CHAPTER 2 TRAFFIC ANALYSIS
2.1 Traffic Movements
The results of the turning movement counts which show the movements by vehicle type at the main intersection in the study area are given in the Appendix to this report. The tables and graphs given therein show the following:
• Hourly total of all vehicle types for each approach and the ADT for each approach • Graph showing the variation of flow by each vehicle type for each approach • Graph showing the variation of flows by each approach for all vehicle types
The summary of these flows are given in Table 2-1. It can be seen that this intersection has an Average Daily Traffic (ADT) of nearly 50,000 vehicle movements per day. Of this, private vehicle flows contribute around 75% of the flow.
Table 2-1: ADT at Stafford Avenue/A4 Junction
Junction ADT Private Buses Goods Non Motorized Total Passenger Vehicles Vehicles Vehicles TM10 41,694 3,298 3,010 953 48,955
The traffic flows on the links connecting this junction is shown in Table 2-2. The main links on the Colombo-Ratnapura (A4) Road have two directional flows ranging between 39,600 to 41,500 on either side of the junction. The Stafford Avenue has around 16,600 vehicles per day.
Table 2-2: Flows on Links
Junction (Approach Flows) Road
Private Buses Goods Non Total Passenger Vehicles Motorized Vehicles Vehicles A 34,832 3,181 984 697 39,694 B 34,884 3,102 2,722 828 41,536 C 13,671 313 2,313 381 16,678
TM10: Stafford Junction
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Hourly Traffic Flow by Vehicle Type 2500
2000
1500
1000 Hourly Traffic Flow Traffic Hourly 500
0 6.30 7.30 8.30 9.30 10.30 11.30 12.30 13.30 14.30 15.30 16.30 17.30 Time Car/Van/Jeep 3 Wheeler Motor Cycles Buses Trucks (6 Axle) Trucks (4 Axle)
Figure 2-1: Hourly Traffic Flow by Vehicle Type
Hourly Traffic Flow by Turning Movement
2000
1800
1600
1400
1200
1000
800
Hourly Traffic Flow Traffic Hourly 600
400
200
0 6.30 7.30 8.30 9.30 10.30 11.30 12.30 13.30 14.30 15.30 16.30 17.30 Time
A : Maya Avenue (From Thimbirigasyaya) 1 - Through A : Maya Avenue (From Thimbirigasyaya) 2 - Left B : Maya Avenue (From Kirullaponne) 3 - Through B : Maya Avenue (From Kirullaponne) 4 - Left C: Stafford Avenue 5 - Right C: Stafford Avenue 6 - Left
Figure 2-2 : Hourly Traffic Flow by Movement
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Hourly Traffic Flow Distribution on Each Road Link of the Intersection 4000
3500
3000
2500
2000
1500
1000
500
0 6.30 7.30 8.30 9.30 10.30 11.30 12.30 13.30 14.30 15.30 16.30 17.30
A : Maya Avenue (North Link) B : Stafford Avenue C: Maya Avenue (South Link)
Figure 2-3 : Hourly Link Flow
Figure 2-4 shows the composition of the approach flow by each vehicle type as well as the total ADT by link of the road network in the study area. This shows the heavy concentration of passenger vehicles on all three approach arms. Especially the Stafford Avenue which does not carry a bus route has 82% of its flow made up of car/vans/jeeps and three wheelers while another 14% are goods vehicles.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
A: ADT of Passenger Vehicle Flows in the study area
B: ADT of Non-Motorized Vehicle Flows in the study area
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C: ADT of Bus Flows in the study area
C: ADT of Goods Vehicle Flows in the study area
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
C: ADT of Total Flows in the study area
Figure 2-4: Traffic Flow Diagrams (ADT by major vehicle groups)
While the directional split on the Colombo-Ratnapura (A4) Road is around 50/50, the Stafford Avenue has a different directional split (61/39) carrying more traffic into Stafford Avenue from the junction. This is due to two reasons:
• The Section from Pamankada Bridge to Havelock Road on Dutugemunu Road is made one way towards Colombo from 7 am to 9 am. This results in Stafford Avenue being used by traffic going towards Kohuwela.
• The evening peak also sees a heavy right turn movement from the Colombo-Ratnapura (A4) Road to Stafford Avenue as most vehicles prefer to use Stafford Avenue in order to avoid the congested Pamankada Junction.
The total amount of motorized passenger vehicles passing the junction is around 41,695 vehicles. This is 85% of the total traffic (ADT) of the junction. The Stafford Avenue link carries 13,670 motorized passenger vehicles which is 82% of the total in that link.
Total ADT of non motorized vehicles is only 953 which make it less than 2% of the total vehicular flow at the junction. Of this the Stafford Avenue carries only 140 bicycles in both directions. These figures are very insignificant when compared with the total ADT of the junction.
A total of 3,300 buses were found to be using the Stafford Avenue/A4 junction daily. Less than 10% (271) of these buses used the Stafford Avenue with only 42 buses exiting on to the Colombo-
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Ratnapura (A4) Road at the Stafford Avenue/A4 junction. This is mostly due to the am peak period one way systems and the compulsory diversion of buses moving outwards from Colombo having to travel on Stafford Avenue.
There are also 3,010 goods vehicles handled by the Stafford Avenue/A4 Junction. An important observation is that 77% (2,313) of these goods vehicles use Stafford Avenue. There are 1,996 (86%) of the goods vehicle movements on Stafford Avenue appearing to be destined to and from the Baseline Road. The reason for this comparatively heavy flow seems to be that the road connection from Baseline Road via Robert Gunawardena Mawatha and Balapokuna Road being narrow and windy and unsuitable for heavy trucks. Therefore a large proportion of trucks taking Galle Road as well as Horana Road coming from destinations such as Pettah as well as from destinations north of Colombo use the Stafford Avenue junction. This means that after the Baseline Phase III is implemented; all these trucks would not be required to travel through the Stafford Avenue.
2.2 Pedestrian Movements
The pedestrian movements recorded on all links and across all approaches at the Stafford Avenue/A4 junction is very low as shown in Figure 2.5. This is mostly due to the fact that there are no intense traffic generators in the immediate vicinity of the junction, even though the Kirulapone Town has intense pedestrian activity during the day time with large amount of commercial and administrative activities such as banks, market, police station, etc in the vicinity. Since the bus halts are away from the junction, and also since there are no bus routes on Stafford Avenue pedestrian flows also tend to be low which would other wise have led to heavy passenger transfer movements as pedestrians. The present sidewalks provided on the Colombo-Ratnapura (A4) Road are of an adequate width for the above pedestrian flow but at present there are no facilities on Stafford Avenue for pedestrians.
Table 2-3 : Hourly Pedestrian Flow
Location Alongside Across
Stafford Avenue 183 86
A4 Nugegoda Approach 81 125
A4 Colombo Approach 188 244
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Figure 2-5: Average Hourly Pedestrian Movements at Junction
2.3 Speed and delay
Travel Time observations at this junction were obtained using 26 different travel passes starting from Saranankara Road /Dutugemunu Road (B084) junction ‰ Stafford Avenue ‰ Stafford Avenue/High Level (A4)Road junction ‰ High Level / Pamankada Rd. junction ‰ Pamankada/B084 Road Junction. These locations are shown in Figure 2-6.
The total length of this circuit measured by Distance Measuring Equipment is 1.557 km. The travel time taken for travelling each section for each pass is given in Table 2-4 and the calculated speed for each section is given in Table 2-5. There are several noteworthy observations to be made from these calculations:
Table 2-4: Summary of Link Travel Time (seconds)
Run Direction 1 Direction 2 Cumulative Section Section of Section Length of Travel (kms) Average Minimum Maximum Travel Average Minimum Maximum A - B 0.048 16 6 40 A - B 16 6 25 B - C 0.653 83 65 107 B - E 84 61 136 C - D 0.698 11 7 19 E - D 74 49 113 D - E 1.023 48 23 68 D - C 69 10 225 E - B 1.509 109 68 194 C - B 101 66 184 B - A 1.557 16 7 77 B - A 25 5 132
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Table 2-5: Summary of Link Speed (km/hr)
Direction 1 Direction 2 Cumulative Section Section of Section Length of Travel (kms) Average Minimum Maximum Travel Average Minimum Maximum A - B 0.048 12 4 22 A - B 15 4 29 B - E 0.653 26 20 30 B - E 22 13 29 E - D 0.698 15 9 23 E - D 17 10 24 D - C 1.023 28 17 51 D - C 4 1 16 C - B 1.509 16 9 26 C - B 23 12 33 B - A 1.557 15 2 25 B - A 17 2 35 A Saranankara Road/B084 Junction B Stafford Av/B084 junction C Stafford Av/A004 junction D Pamankada Road/A004 junction E Pamankada Road/B084 junction
Travel time survey was carried out along the selected road links (marked by points as H1, H2, H3 and A, B, C, D, E) as shown in Figure 2-5. The survey was carried out on the Colombo-Ratnapura (A4) Road in both directions and other road links for both clockwise and anti-clockwise travel directions of the loop shown in Figure 2-5. The estimated average speeds according to this survey are given in Table 2-6 and Table 2-7.
The average speed on the Colombo-Ratnapura (A4) Road south bound at Maya Avenue (Section -H1- H2) in both directions is above 23km/h. But this is only around 15km/h south of the A4 towards Kirulapone Junction (Section - H2 – H3). This includes approach delays to signals on both links. It is clear that the lower speed on the southern approach to Stafford Avenue has lower speeds due to the lack of road capacity. The average speed of the northbound approach to Stafford Avenue Junction from Kirulapone Police Station records is even lower at 13km/hr (Table 2-6). The apparent reason is the reduced capacity at the Kirulapone Bridge which only has two narrow lanes leading to long traffic queues at the traffic signals.
It is observed that section A-B on Dutugemunu Street represents a four way junction with two “Y” junctions on either side of the Pamankada Bridge. Therefore the speed (average of 16km/hr) at this section has greatly reduced due to stopping and turning of vehicles. Section B-E on Havelock Road is narrow with poor horizontal and vertical alignment. It has a higher speed in the northbound direction possibly due to the one way system operating during the morning when the flow is higher.
The section D-E also shows an imbalance of speeds in the two directions due to this reason. The average speed of the right turns at Stafford Avenue/A4 junction from Maya Avenue to Stafford Avenue (from H to C – a section of around 40 meters) is 4km/h with the signal delays. The returning flow as the left turns from Stafford Avenue to Maya Avenue is 15km/h. The average speed of Stafford Avenue from C to B which is nearly 500 metres is 24km/h while in the opposite direction this is only 14km/h as it includes the stop time delay due to the traffic signal. These slow speeds are mostly due to
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report vehicles approaching from Pamankada wishing to travel south bound on the Colombo-Ratnapura (A4) Road having to make a right turn and cross the A4 to enter the Stafford Road junction.
There is no capacity problem on the mid section of the Stafford Avenue at present. However, there are capacity limitations at both ends and speeds are found to reduce significantly especially during peak periods in the peak direction.
Figure 2-6: Locations and Road Sections for Travel Time Survey
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Table 2-6: Average Travel Speed at High Level Road
Speed of Sections at HighLevel Road (km/h) Trial No Start Time H1 - H2 H2 - H3 H3 - H2 H2 - H1 Trial 1 7:58:24 16 18 18 4 Trial 2 8:10:28 23 21 6 11 Trial 3 8:17:18 18 30 8 23 Trial 4 8:22:14 30 29 10 30 Trial 5 12:48:14 2 3 6 18 Trial 6 15:58:5 35 26 10 19 Trial 7 16:2:37 28 22 10 32 Trial 8 17:16:51 35 15 6 26 Trial 9 17:44:40 18 10 20 24 Trial 10 17:49:30 32 13 20 25 Trial 11 18:15:45 28 14 24 35 Trial 1218:37:5 22 13 13 24 Length of Section (m) 510 190 190 510 Average Speed (km/h) 24 18 13 23 Coefficient of Variation 39 45 50 38 Legend Point Location of Travel Time Survey Points H1 Maya Avenue /Havelock Road Junction H2 Stafford Road /High Level Road Junction H3 Kirrillapone Police Station Junction
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Table 2-7: Average Travel Speed at Other Road Links
Speed in Clockwise Direction of Sections (km/h) Trial No Start Time A - B B - E E - D D - C C - B B - A Trial 1 7:36:13 19 26 19 1 29 22 Trial 2 7:45:20 11 26 11 2 29 29 Trial 3 7:56:10 22 29 21 2 24 2 Trial 4 8:06:15 17 21 19 2 27 1 Trial 5 11:36:30 29 13 10 2 29 35 Trial 6 12:25:29 19 20 15 3 33 22 Trial 7 13:37:47 25 22 18 3 25 12 Trial 8 13:51:22 17 22 17 3 27 19 Trial 9 14:38:07 17 23 24 2 28 22 Trial 10 16:05:18 12 22 20 10 28 25 Trial 11 16:41:43 17 13 11 16 24 17 Trial 12 17:20:40 5 26 16 4 12 10 Trial 13 17:52:20 4 24 18 3 13 12 Trial 14 18:32:01 9 20 16 5 12 10 Length of Section (m) 48 486 325 45 605 48 Average Speed (km/h) 16 22 17 4 24 17 Coefficient of Variation 46 20 23 101 28 57
Speed in Anti-clockwise Direction of Sections (km/h) Trial No Start Time A -B B - C C - D D - E E - B B - A Trial 1 7:03:20 22 34 20 30 23 25 Trial 2 7:08:10 29 26 16 25 22 25 Trial 3 11:28:30 22 30 16 21 24 2 Trial 4 12:20:21 22 20 16 23 20 19 Trial 5 13:33:15 12 23 16 24 26 25 Trial 6 13:45:15 14 23 9 27 17 19 Trial 7 14:32:04 8 24 9 17 18 19 Trial 8 15:59:46 22 28 16 19 22 12 Trial 9 16:36:28 17 29 23 22 17 19 Trial 10 17:08:30 5 28 15 25 10 12 Trial 11 17:40:20 4 28 14 28 10 12 Trial 12 18:24:19 9 27 14 51 9 12 Length of Section (m) 48 605 45 325 486 48 Average Speed (km/h) 15 27 15 26 18 17 Coefficient of Variation 51 14 27 33 31 40 Legend Point Location of Travel Time Survey Points A Saranankara Road /Dutugemunu Road (B084) Junction B Stafford Road /Havelock Road Junction C Stafford Road /High Level Road Junction D High Level Road / Pamankada Road Junction E Pamankada Road / Havelock Road Junction
Hence the average speed of the Colombo-Ratnapura (A4) Road section from Kirulapone Police Station to Maya Avenue / Havelock Road Junction over a length of 700 meters is 18km/h. This is 21 km/h in the other direction. The average speed of the Stafford Avenue from Havelock Road end to the Colombo-Ratnapura (A4) Road over a length of 605 meters is 27 km/h. This is 24 km/h in the opposite direction over a distance of 650meters.
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2.4 Accident Studies
A limited amount of accident statistics could be collected from the Kirulapone Police Station representing the recorded traffic accidents in the study area. A summary of this is shown in Table 2.8. This shows that for the first half of 2008, there have been 3 grievous injuries on the Colombo- Ratnapura (A4) Road between the Stafford Av and Baseline Road Junction. There have been a total of 15 recorded accidents. These figures do not indicate a major problem of accidents at this junction.
Table 2-8 : Accident Statistics in the Study Area
Location Accident Type Total
Light Property Year Road From To Fatal Grievous Injuries Damages Total Accidents in the Study Area Kirula Mw to High level 3 Stafford Av (towards 0 12 15 9/31/2008 road Nugegoda) Total Accidents in the Police Divisional Area
2006 6 8 27 96 137
2007 7 10 33 67 117 9/31/2008 1 5 35 66 107
2.5 Road Infrastructure
The road infrastructure in the study area is mainly the Colombo-Ratnapura (A4) Road, Stafford Avenue, and Pamankada Road. The Colombo-Ratnapura (A4) Road is a 4 lane road but, it has 5 lanes close to the Stafford Avenue Junction. This road has adequate sidewalks which are in satisfactory condition. The commercial development alongside the road is moderate density and therefore the pedestrian movements are not as heavy as experienced at other busy junctions.
The other important road link at this signalized junction is Stafford Avenue which has two lanes and is undivided. This road has not been provided with adequate sidewalks for pedestrians except for a very short length close to the junction. The commercial development along this road is dense and many roadside activities disturb the present traffic movements during the day time. This is mostly due to the heavy demand for parking throughout the Stafford Avenue. The road surfacing too is not very satisfactory compared to the Colombo-Ratnapura (A4) Road.
Pamankada Road in comparison carries much less traffic. It is also a very narrow road (Figure 3.4) with number of commercial activities and frequent parking along the road which is one reason to discourage vehicular use. The road link between the Pamankada Road and the Pamankada Bridge is also sub standard 2 lane with narrow lane widths. This also has poor horizontal alignment with short curves and vertical gradients which discourage the travel on it and also reduces speeds. This too has an effect to encourage the use of Stafford Avenue as an alternative.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
The Baseline Road connection to the Colombo-Ratnapura (A4) Road at Kirulapone which is only 250 meters away from the Stafford Avenue has a significant impact on the traffic flows at Stafford Avenue Junction. The road to Dutugemunu Street via Robert Gunawardena Mawatha and Balapokuna Road is also a sub standard 2 lane. The geometric details of the roads mentioned above are found in Table 2-9.
Table 2-9: The cross sectional details of the road links in the study area
Width of Road Sectional Elements (m) Map Item # Gap to Total Road Name and Section Reference Walkway/ No Lanes Lane Drain Building (Wall to No Shoulder Edge Wall) 1 High Level Road (North to Staford Road ) A-A 6 3.00 1.40 0.60 23.00 2 High Level Road (On the Kirillapone Bridge) B-B 4 3.50 3.00 22.00 3 High Level Road (Maya Avenue) C-C 4 3.25 2.25 0.60 1.00 21.70 4 Staford Road D-D 4 3.00 2.40 0.75 19.00 5 Pamankada Road E-E 2 3.40 0.60 8.00
Figure 2-7: Road Link and Lane configuration of Stafford Avenue Junction
2.5.1 Highway Geometry of the Study Area
Both approaches on the Colombo-Ratnapura (A4) Road to the junction have curvatures. The radius of curvature of the Colombo approach is around 65meters radius. This is 345meters for the Nugegoda approach. Stafford Avenue approaches the junction at right angles to the A4. The A4 Road is generally designed for 4 lanes. The lane capacity of the Colombo approach of the A4 Road at the
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report junction is 5 lanes while this is 4 lanes for the Nugegoda approach over the bridge. Stafford Avenue approach has sub standard 4-lane configuration at the junction while it is 2 lanes elsewhere. The bridge across the Kirulapone Canal on A4 Road is at the Nugegoda approach of the signalized junction has a span of 24 meters. Even though this bridge has wide sidewalks on either side, the carriageway widths provided are very narrow with a center median as well.
2.5.2 Delay due to Existing Traffic Signals and Lane Geometry
The average hourly stopping rate of vehicles on the Nugegoda approach of the A4 for the traffic signal at the Stafford Avenue/A4 junction is 445 vehicles per hour. This does not vary by much throughout the day. This is always more than the double the number of vehicles affected by the stop light on the other two links. It clearly observed that the reason for this is the inadequate number of lanes (only two lanes for both through and left turns) on the bridge. The analyzed cycle time of the signalization with a three phase system for the current traffic flow is given in Figure 2-8.
For the Maya Avenue approach, a lagging right turning phase has been provided in the existing traffic signal system. According to the stop time data for signals at the junction, the cycle time has been above 120 seconds. Also as the separate right turn from the A4 Road is only from Maya Avenue approach, and operate with the through movement together the green time allotted for the Kirulapone approach is lower when compared to that of the Maya Avenue approach. This has aggravated the problem at the Kirulapone approach where the traffic flow level is higher than the capacity provided by the two lanes which are available for all movements.
Calculated Cycle Time (Stafford Road Junction - Existing Situation) 200 180 160 140 120 100
Cycle Time Cycle 80 60 40 20 0 06.45 07.15 07.45 08.15 08.45 09.15 09.45 10.15 10.45 11.15 11.45 12.15 12.45 13.15 13.45 14.15 14.45 15.15 15.45 16.15 16.45 17.15 17.45 ------06.30 07.00 07.30 08.00 08.30 09.00 09.30 10.00 10.30 11.00 11.30 12.00 12.30 13.00 13.30 14.00 14.30 15.00 15.30 16.00 16.30 17.00 17.30 Time
Figure 2-8: Calculated variation of Signal Timing during the day at Stafford Road Junctions with Existing Layout
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The estimated delay due to the signalization at the given flow levels and phasing and cycle time arrangements and existing lane geometry calculated through Blink 2005 is 1,176,355 vehicle seconds (327 vehicle hrs) for a 12 hour period from 6.30am to 6.30 pm. This translates to an average delay of 24 seconds per vehicle. This delay is quite high and enhances the need of improvements to both signal timing and the lane geometry at this junction.
Table 2-10: Present Delay at the Signal at Stafford Avenue/A4 Junction
Queue Length (Number of Vehicles) by RED STOP at Signal from the Approach of: Time Maya Avenue Kirillapone Stafford Road At a Stop Total in 15min At a Stop Total in 15min At a Stop Total in 15min 6.30-6.45 6+2+7+4+4+4+6 33 6.45-7.00 5+8+4+8+7+7 39 7.00-7.15 10+11+9+11+12 53 7.15-7.30 9+6+13+12 40 7.30-7.45 24+48+46 118 7.45-8.00 44+32+43 119 9.30-9.45 12+11+8+16 47 9.45-10.00 14+13+12+10 49 10.00-10.15 6+7+7+5+6+7 38 10.15-10.30 6+5+7+8+7+5 38 10.30-10.45 27+36+33+26 122 10.45-11.00 32+27+31+25 115
14.00-14.15 10+12+14+6+7+8 57 14.15-14.30 9+14+16+14+12 65 14.30-14.45 10+12+7+9+8 46 14.45-15.00 6+9+10+7+8 40 15.00-15.15 21+27+32+20 100 15.15-15.30 15+22+30+26 93 17.00-17.15 8+7+8+6+9 38 17.15-17.30 9+16+12+14 51 17.30-17.45 18+21+17+14 70 17.45.18.00 16+14+18+22+14 84 18.00-18.15 30+24+26+38 118 18.15-18.30 27+19+32+27 105 Average 51 111 47 Av: # Vehicles Stopped per Hour 205 445 190
2.6 Summary of Observations
The following is a summary of problems identified in this section:
• This T junction is 250 metres north of the intersection of Baseline Road with the Colombo- Ratnapura (A4) Road.
• There are almost50,000 vehicle movements at this junction. The ADT on the A4 is around 40,000. The ADT on the Stafford Avenue is 16,600.
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• There are on average around 250 pedestrian crossings per hour on all the roads at the junction. This is comparatively low given the fact that there are no transfer bus passengers or high traffic generators close to the junction.
• The heavy vehicle percentage on Stafford Avenue is around 14% denoting a heavy truck movement. The majority of these trucks are those travelling between Baseline Road and Galle Road/Horana Road which take the Stafford Avenue since the Baseline Road Phase III is yet to be completed.
• There is a traffic flow imbalance on Stafford Avenue due to a one-way system being operated during the am peak period.
• There are sidewalks of adequate capacity on the Colombo-Ratnapura (A4) Road However Stafford Avenue does not have sidewalks.
• Since parking is not been allowed on the Colombo-Ratnapura (A4) Road adjacent to the junction, there are no parking related impacts on the movement of traffic on the A4.
• The primary issue at these junctions is the heavy right turns of traffic approaching on A4 from Colombo. This is mostly due to the poor condition of Dutugemunu Street between Pamankada Bridge and Pamankada Junction. Due to frequent blockages at Pamankada junction, most drivers prefer going up to Stafford Avenue junction and making a right turn.
• The average speed through the junction varies by approach. The speed on Stafford Avenue entering the junction is 24 km per hour, while the right turns from the Colombo approach on the A4 to Stafford Avenue is 14 km/km.
• The speeds during peak periods do not vary very much except at the Pamankada Bridge in the peak direction which reduces to less than 10 km per hour during the evening peak.
• The primary reason why this junction gets blocked is the large volume of right turns from Stafford Avenue to the Colombo-Ratnapura (A4) Road towards Nugegoda. This traffic which constitutes a significantly higher proportion of goods vehicles are mostly intended for journey on Baseline Road. Hence the primary issue at this junction is the problem arising from the absence of Baseline III and the impact due to the nature of traffic moving to it from Horana (B84) and Galle (A2) roads.
• The road right of way widths vary for each approach. In the case of the A4 road, it is between 21 to 23 metres and function as a 5 lane highway from the Colombo approach. It is however only 4 lanes approaching from Nugegoda due to the bottleneck of the bridge. The A4 is divided by a centre median. In the case of the Stafford Avenue approach the right of way
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
width is 19 metres, and provides for 3 lanes. The Pamankada Road has an approach width of only 8 metres and functions as a 2 lane road.
• The lane marking at the junction is satisfactory, but the turning circle is tight reducing all speeds, particularly all left turns.
• The junction is presently controlled by a traffic signal with a 3 phase- timing. The average delay at this junction at present is around 24 seconds per vehicle.
• The am peak hour load at the junction is 4,115 vehicle movements and 175 pedestrian movements. The pm peak load is 4,147 vehicle movements and 296 pedestrian movements.
• There are no fatal accidents recorded for first nine months of 2008 in the study area. There have been 3 grievous accidents of a total of 15 accidents reported during this period. This does not indicate that there is a major concern regarding accidents at this junction.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
CHAPTER 3 SOLUTIONS
Solutions to the problems of congestion at Stafford Avenue/A4 Junction can be identified as belonging to three distinct categories:
• Localized Solutions
• Area Wide Solutions and
• Network Solutions
The localized solutions include solutions that are confined to the junction and its immediate vicinity only. The Area-wide solutions are the improvements that may be effected in the entire road network within the study area, which in this case extends to Pamankada Bridge, Pamankada Junction and Maya Road/Havelock Road Roundabout. The Network solutions refer to improvements that can be made to the wider road network even outside the study area whereby the congestion at this junction can be reduced.
3.1 Localized Solutions
3.1.1 Widening of Bridge and Improvements to Signalized Junction
The capacity of the Colombo-Ratnapura (A4) Road at the Stafford Avenue/A4 junction is 4 to 5 lanes even though it has 6 lanes on either approach away from the junction and the right of way width of between 22 to 23 metres being available. This causes a bottleneck and results in heavy traffic congestion during most times of the day and becoming chronic during peak hours in both directions.
The approach capacity of the A4 from Nugegoda has to be increased to 3 lanes. Since this involves the bridge, widening of the bridge is required. This could be done by the widening at least the down- stream side (western side) as shown in Figure 3.1. Therefore, there will be 3 lane approach capacity up to a distance of around 150 meters on both sides of the A4 Road. The widening of the eastern side will also provide 3 lanes for traffic towards Nugegoda and also improve the speeds of left turning traffic from Stafford Avenue. Further widening to 6 lanes on Colombo approach though desirable will require acquisition and demolition and will be constrained by the presence of a Bo Tree.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Figure 3-1: Improvements to junction and widening of the Bridge on A4
According to the observed traffic flow at the junction, the right turning traffic from Stafford Avenue at any time period is 2 to 3 times more than the left turns. Therefore it is reasonable to provide two right turn lanes and one left turns to ease the traffic flow at signal timing design. The left turn from Kirulapone to Stafford Avenue is also very significant. Therefore it is important to provide separate left lane to pass the additional flows during the right turn phase of the Maya Avenue approach. This could be allowed with an island as shown in Figure 3.1 and can be facilitated using the space gained from widening the bridge. This will help to improve the speed of the turning traffic as well as the through traffic flow capacity on the A4. The largest right turn flow at the junction is from High Level Road (A4) to Stafford Avenue. With less time required for Stafford Avenue green times, the turning traffic from High Level to Stafford Road could be given more green time thus reducing delays. The proposed improved junction has an area of 18m x 13m. A minimum lane width of 3meters for all lanes could be provided at the junction with the new improvements. Therefore this lane arrangement with new traffic signal timing can be used to improve the traffic flow situation in the junction very significantly.
The Stafford Avenue Junction has a total of 48,954 of ADT. More than 70% of traffic approach from Stafford Avenue to the “T” Junction turns right at the junction. This imbalance should be treated during traffic signal design at this junction. Therefore the geometric design proposed in Figure 3.1 may help to improve the capacity of the junction by re-phasing the signal design.
The revised signal design using Blink 2005 can also be provided a three phase arrangement. Results (Figure 3-.2) show that the cycle time could be kept as low as 60 seconds during most of the time period of the day. It needs to be increased to 180 seconds only for half an hour period from 7.45 am to 8.15am during morning peak. The increase during the evening peak is to 90 seconds from 5.15pm to
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
6.00pm. The intersection delay with this arrangement is estimated as 367,630 vehicle seconds (102 vehicle hours) per 12 hour period of a day. Therefore, there is a savings of 225 vehicle hours (327hrs - 102hrs) for a 12 hour period of a day with this improvement from the existing situation. This would reduce average vehicle delays from 24 seconds to 7 seconds.
Adjusted Cycle Time (Stafford Road Junction - After Improvements) 200 180 160 140 120 100
Cycle Time Cycle 80 60 40 20 0 30 00 30 00 00 30 00 30 00 30 00 30 00 30 00 30 00 30 00 00 30 00 ...... 06 07 07 08 08.30 09 09 10 10 11 11 12 12 13 13 14 14 15 15 16 16.30 17 17 18 ------15 45 15 45 45 15 45 15 45 15 45 15 45 15 45 15 45 15 45 45 15 45 ...... 06 06 07 07 08.15 08 09 09 10 10 11 11 12 12 13 13 14 14 15 15 16.15 16 17 17 Time
Figure 3-2: Calculated variation of Signal Timing during the day at Stafford Road Junction with Improved Layout (Blink 2005)
The traffic management on approaches to the junction should also be improved. For this purpose on- street parking should be limited. Some off-street parking should be developed for parking taking place on the Nugegoda approach as well as on Stafford Avenue.
For a widening of a single lane there are only 1 or 2 buildings that need to have minor demolitions as most of the road length has adequate reservations as shown in Figure 3-1.
3.2 Area Wide Solutions
It is possible to reduce the traffic load to the junction by improving other road links in the study area. These are described below:
3.2.1 Widening of Pamankada Bridge
This presently has only two lanes and is located between two Y junctions. The traffic levels at this junction warrants that it be widened to at least 4 lanes with signalization of a rotary type (such as at
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Maradana). This will reduce congestion of traffic heading back from Colombo on Havelock Road and with the improvement in speeds will reduce the amount of traffic that is now getting diverted through Stafford Avenue/A4 junction and Stafford Avenue. This will ease the congestion at the Stafford Avenue/A4 junction since right turns which are critical in the cycle time determination will be reduced thus yielding time savings to all vehicles especially to those on A4 which is a primary artery.
3.2.2 Improvement to Pamankada Junction
Improvements to Havelock Road have begun and have proceeded from Maya Avenue Roundabout to the Pamankada junction. The junction itself is now a bottleneck. The Havelock Road from the junction down to the Pamankada Bridge is ear marked for widening to 4 lanes (Figure 3-3). If this is carried out together with the improvement to the Pamankada Bridge then the re-routing traffic on Stafford Road will reduce entirely and there would be no additional load at Stafford Avenue/A4 junction. This should include properly designed bus bays as well as signalization of the Pamankada Junction.
It is possible that around 7,000 PCUs per day will be reduced from the Stafford Avenue/High Level Road junction. This will in effect be around 15% reduction of the traffic load at the junction.
Figure 3-3: Proposed Improvements to Pamankada Road and Pamankada Bridge
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
The signal time of the existing Stafford Road / Colombo-Ratnapura (A4) Road Junction can be adjusted with 80% less right and left turns from and into Stafford Avenue respectively. Accordingly the recalculated signal design analysis indicates that the three phase system can be made a two phase system by avoiding a separate right turn phase from Maya Avenue to Stafford Avenue. The signal time delay will then reduce from 327 hours to 145 hours without an improvement to the existing lane geometry. This is a 56% reduction of the signal delay of the existing system for a 12 hour period.
3.3 Network Improvement Solutions
The other heavy traffic movement that congests the Stafford Avenue Junction is the traffic that is bound to/from Galle Road and Horana Road from Baseline Road. The solution to this is the extension of Baseline III (Figure 3-4). This will reduce almost all of the right turns from Stafford Avenue. These right turns are also part of the signalized time which is critical. Hence reducing the right flows will be a definite way of reducing the overall delay at the junction. One specific advantage of this will be the reduction of goods vehicles now using the Stafford Avenue/A4 junction.
In this respect it was observed that 89% of the good vehicles that use Stafford Avenue are travelling to or from the Baseline intersection. Therefore the need of the Baseline Phase III is very important to implement at this stage. This could be implemented by stages. Initially the Baseline Road from the High Level intersection can be connected to Horana Road and via this road to Galle Road via the Saranankara Mawatha.
The flow of vehicles that would be diverted from the High Level Road/Stafford Avenue Junction would be around 10,000 PCUs per day. This would translate to a reduction of the traffic load at the junction of around 15%.
Figure 3-4: Proposed Improvements to Pamankada Road and Pamankada Bridge
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
The signal time of the existing Stafford Road / High level Road Junction can be adjusted if the above reduction of right turns and left turns could be reduced. According to the recalculation for the signal design analysis, the signal time delay will reduce from 327 hours to 124 hours without improvement to the existing lane geometry. This is a 62% reduction of the signal delay of the existing system for a 12 hour period.
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Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
CHAPTER 4 ECONOMIC ANALYSIS
4.1 Costs
The cost of the localized solutions proposed in the above chapter will include the following
• Signalization of intersection including acquisition • Widening of Bridge • Widening and Improvements to the approach roads, realignment, construction of signs and road markings.
The following general works are also recommended.
• Improvements to the carriageway and resurfacing of approach roads up to intersection. • Reconstruction and improvements to Sidewalks on above sections • Improvements to Traffic Management measures in the study area including access control, guard rails, etc.
The cost estimates for the localized solutions are shown in Table 4.1. These are based on three main items namely, acquisition and reconstruction cost, general civil work for the road items and the widening of one side of the bridge on A4 Road. Widening of the bridge is possible since it is not joined to the existing capping beams, and constructed as a separate bridge, no loading problems to existing one.
4.2 Benefits
Economics benefits from this project are many fold. For the purpose of this study we will include the following benefits:
• Reduction in Vehicle Operating Costs from improvements to the junction. • Travel Time savings from improvements to the junction.
There does not seem to high accidents at this junction to claim savings in reducing accidents.
4.2.1 Traffic Analysis
In computing the above benefits the traffic analysis has considered the following.
The present travel speeds reported in Chapter 3 can be summarized as follows: • Colombo-Ratnapura (A4) Road (Maya Avenue) approach speed – 20 km/hr • Colombo-Ratnapura (A4) Road (Nugegoda) approach speed – 14 km/hr • Stafford Avenue approach speed - 14 km/hr
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The signalization delay for the present 3 phase arrangement was estimated at 1,176,355 vehicle seconds. This works out to around 24 seconds per vehicle. The intersection delay with the localized improvements is estimated as 367,630 vehicle seconds per 12 hour period of a day. Therefore, there is a savings of 225 vehicle hours (327 hrs – 102 hrs). This would reduce average vehicle delays from 24 seconds to 7 seconds.
Table 4-1: Cost Estimates of the Improvements
Widening of the Bridge and Improvement to the Signalized Item Description Unit Rate (Rs) Junction Item No Item Qty Amount (Rs) 1.0 Land Acquisition, & Demolition and Reconstruction 1.1 Road Length m 400 1.2 Single Storey m2 40000 50 2,000,000.00 1.3 Two Storey m2 100000 40 4,000,000.00 1.4 Three Storey m2 160000 50 8,000,000.00 1.5 Total Land m2 75000 140 10,500,000.00 Sub Total 1 24,500,000.00
2.0 General Civil Cost 2.1 Preliminaries Sum 3,000,000.00 2.2 Clearing m2 80 600 48,000.00 2.3 Base & Sub Base m2 850 1455 1,236,750.00 2.4 Asphalt Surfacing m2 2,300 6900 15,870,000.00 2.5 Walk Ways m2 900 700 630,000.00 2.6 Kerbs m 1,450 8400 12,180,000.00 2.7 Drains m 4,600 100 460,000.00 2.8 Fencing and Barricades m 14,000 200 2,800,000.00 2.9 Road Markings m 100 1400 140,000.00 2.10 Sign Boards Nos 35,000 20 700,000.00 2.11 Relocation of Traffic Signal Unit Nos 900,000 1 900,000.00 Sub Total 2 37,964,750.00
3.0 Expansion of Bridge m 125,000 156 19,500,000.00 Sub Total 2 19,500,000.00
Total 81,964,750.00 Add for Variations (20%) 16,392,950.00 Grand Total 98,357,700.00
If we make the assumption that after improvements the approach speeds will be as shown in Table 4-2 then we observe that the reduction in delays equals to 235 hours per day, which is equal to the signal timing delay when an additional 10 vehicle hours time savings is provided for other approach geometry related improvements.
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Table 4-2: Computation of Improved Speeds and Time Savings
Distance Time Approach (m) ADT Speed (km/hr) Savings
Existing Improved Veh Hrs
A4 Maya Avenue 350 20,951 20 22 33
A4 Nugegoda 240 21,490 14 20 111
Stafford Avenue 653 6,513 14 20 91
TOTAL 235
4.2.2 Economic Benefits
Table 4-3 shows the computation of economic costs and benefits for the junction signalization and improvement option. The calculations are based on a ‘before and after’ traffic flow estimate taking into account the flow estimates given in Section 4.2.1 for private vehicles, goods vehicles and buses separately. The cost estimation uses unit values from ‘Assessing Public Investment in the Transport Sector’ 1. These include vehicle operating costs at given speeds wherein the roughness was assumed at IRR =3. The Value of Time for passengers was taken after considering Vehicle Occupancy Rates (VOR) and the Value of Time (VoT) from the above reference after adjusting for price escalation using CCPI. All estimates shown in Table 4-3 is in SLR in 2008 prices.
1 National Planning Department, Authored by Kumarage A.S., Ed Storm, T.L. Gunaruwan et al, 1999
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Table 4-3: Economic Analysis for Signalization & Improvement Option
PRESENT SCENARIO-2008 Vehicle Operating Cost ADT (Average) length speed VOC(Rs/km) Ann. Cost Private Bus Truck Total km km/hr Private Bus Truck Rs Mn Section High Level (Maya Avenue) Approach 18,583 1,532 503 20,618 0.35 20 29.07 56.40 52.38 80.0 High Level (Nugegoda) Approach 17,891 1,724 1,397 21,012 0.24 14 32.67 72.15 66.18 67.3 Stafford Avenue 5,220 43 1,110 6,373 0.653 14 32.67 72.15 66.18 56.5 203.8
Travel Time Costs ADT length speed VOT(Rs/hr) Ann. Cost Private Bus Truck Total km km/hr Private Bus Truck Rs Mn Approach High Level (Maya Avenue) Approach 18,583 1,532 503 20,618 0.35 20 204 1116.9 33.7 High Level (Nugegoda) Approach 17,891 1,724 1,397 21,012 0.24 14 Stafford Avenue 5,220 43 1,110 6,373 0.653 14 204 1116.9 18.2 51.9
VOR VOT Private 1.2 170 Bus 30 1116.9
SCENARIO WITH IMPROVEMENTS Vehicle Operating Cost ADT length speed VOC(Rs/km) Ann. Cost Private Bus Truck Total km km/hr Private Bus Truck Rs Mn Approach High Level (Maya Avenue) Approach 18,583 1,532 503 20,618 0.35 22 28.47 52.44 49.98 77.7 High Level (Nugegoda) Approach 17,891 1,724 1,397 21,012 0.24 20 29.07 56.40 52.38 58.0 Stafford Avenue 5,220 43 1,110 6,373 0.653 20 29.07 56.40 52.38 48.5 184.3
Travel Time Costs ADT length speed VOT(Rs/hr) Ann. Cost Private Bus Truck Total km km/hr Private Bus Truck Rs Mn Approach High Level (Maya Avenue) Approach 18,583 1,532 503 20,618 0.35 22 204 1116.9 30.6 High Level (Nugegoda) Approach 17,891 1,724 1,397 21,012 0.24 20 Stafford Avenue 5,220 43 1,110 6,373 0.653 20 204 1116.9 12.7 43.4
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4.3 Cost-Benefit Analysis
The benefits computed from Table 4.3 are as follows:
• Savings in Travel Time Costs
• Savings in Vehicle Operating Costs
In the case of economic benefits due to generated traffic, no increase in the economic activity of the area has been assumed since the project is of a very local nature and unlikely to generate regional development. Based on the estimates in Table 4-4 an economic analysis has been performed to obtain the Economic Internal Rate of Revenue (EIRR).
This analysis is based on:
1. The assumption that value of vehicle operating costs, travel time and maintenance costs will increase but in a manner that they will remain constant in real terms over the project life.
2. Project Life for the signalization is taken as 10 years after commissioning, and where construction is expected to be completed by the end of 2010.
3. Traffic growth has been assumed at a very conservative 3% growth rate. This is much less than the 4 to 6 percent growth seen in urban areas.
The following conclusions can be reached from this economic analysis:
4.3.1 Signalization & Improvement Option
The summary of the costs and benefits that were discussed in earlier sections and discounted over the project life are given in Table 4-4.
Based on the Table 4-4 it is seen that the Signalization Option the following conclusions can be reached:
1. On the above assumptions it returns an EIRR of 20.7% which can be termed a good return on investment for an urban road project.
2. At a discount rate of 0% it returns a Net Present Value of Rs 202 million over 10 years.
3. At undiscounted prices it returns a Benefit to Cost Ratio of 2.7.
The following sensitivity tests have been also performed:
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1. If construction costs increases by 50% in real terms the project returns an EIRR of 12.2% which shows that the signalization project is robust to absorb cost variations.
2. If benefits reduce by half over the project life period, returns an EIRR of 6% showing the project is adequately robust to absorb reduction in benefits.
Table 4-4: Cost Benefit Analysis for Signalization & Improvement Option
Cost Benefit Capital Recurrent VOC VOT Accidents Generated Total Net 2008 0 0 2009 98 2010 2.0 20 9 0 0 28.0 26 2011 2.0 20 9 0 0 28.9 27 2012 2.0 21 9 0 0 29.7 28 2013 2.0 21 9 0 0 30.6 29 2014 2.1 22 10 0 0 31.6 29 2015 2.1 23 10 0 0 32.5 30 2016 2.1 23 10 0 0 33.5 31 2017 2.1 24 10 0 0 34.5 32 2018 2.2 25 11 0 0 35.5 33 2019 2.2 25 11 0 0 36.6 34 321.4 301 Total
Discount Rate 0.0 Generated Traffic 0.0 NPV 202.0 Rs Million B/C 2.7
3.
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CHAPTER 5 CONCLUSIONS
The following conclusions on the above analysis based on the primary option of improving signalization can be tabulated as follows:
Feature of Impact Improvement to Signalization Option
Solutions • Short Term: Localized Solutions in the form of improvements to geometric capacity by widening of bridge and approaches to improve the Level of Service of the Signalized Junction.
• Medium Term: Area Solutions by reducing traffic diversion through Stafford Avenue by Widening Pamankada Bridge and Pamankada Junction. This will reduce traffic load by around 15% at the junction.
• Long-Term solution will be to extend Baseline Phase III so that traffic moving between Galle Road and Horana Road and Baseline Road will reduce thus reducing total load of the junction by nearly 20%.
Cost of Construction Rs 98 million for a 3 phase signal with widening for 3 lane approaches on High Level Road and 3 lanes from Stafford Avenue approaches.
Urban Landscape No adverse Impact
Cost of Other General Included in above Improvements
Increase in Travel Speed Through traffic speeds on High Level Road (Colombo bound) will increase from 14 km per hour to 20 km per hour
Acquisition Will require minor acquisition along Stafford Avenue
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Economic Benefit-Cost Analysis EIRR at 20.7% and NPV at Rs 202 Million are positive and Benefit-Cost ratio is 2.7.
Safety Not a critical situation at present. No further improvements anticipated.
Level of Service Signal Timing for existing flow returns an acceptable Level of Service
Adequacy of Capacity Will be adequate for next 10 years and up to 20 years if Area Solutions and Network Solutions are implemented.
Delays during Construction Relatively small as construction duration will also be very short
Bus Operations from Terminals No Impacts
Bus Stopping Not applicable
Pedestrian Facilities To be provided as existing with sidewalks on Stafford Avenue
Parking Facilities Off Street parking facilities required for both High Level Roads as well as Stafford Avenue.
This analysis clearly shows that the improvements to the signalization option is a viable option. The medium to long term solutions can then be obtained by the widening of Pamankada Bridge and Pamankada Junction followed by the extension of Baseline Road.
The construction of a flyover is not technically feasible given the adverse impacts to surrounding land use.
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CHAPTER 6 RECOMMENDATION
The following measures to improve the traffic flow on the Colombo-Ratnapura Road/Stafford Avenue Junction can be recommended based on the economic viability and other issues discussed earlier.
• Recommended improvements to signalization. This will require widening of the approach roads to include geometry of 3 lanes on each approach of the Colombo-Ratnapura Roadand a 3 lane approach to Stafford Avenue.
• Improve the pedestrian walkways and control parking close to the junction by constructing guard rails with limited openings to reduce disruption to the free flow of traffic.
• This can be followed by the widening of the Pamankada Bridge and the widening of the Havelock Road and Pamankada Junction so that the traffic routing through Stafford Avenue and Maya Avenue can be taken on Havelock Road via Pamankada Junction. This will reduce the traffic load at the Stafford Avenue Junction by around 15%.
• In the long term, the extension of Baseline Phase III will result in a further reduction of 20% traffic at the Stafford Avenue junction.
These measures will result in
• Improved speeds at the Stafford Avenue/ Colombo-Ratnapura Road junction specifically and within study area in general. Speeds on the approaches to the junction will improve from 14 to 20 km/hr to 20 to 24 km/hr.
• The medium and long term solutions will further improve the speeds.
The project is estimated to cost around 98million rupees but its benefits will far outweigh the costs in terms of an EIRR of 21.7% and an NPV of Rs 202 million at 0% discount rate and a Benefit-Cost ratio of 2.7.
The project will remain moderately stable even if there are unexpected cost variations or reduction of benefits.
The summary of the recommendations are shown in the Figure 6-1.
6-1 | P a g e
Section B3: Stafford Junction Treatment of Junctions- Volume I: Final Report
Figure 6-1: Map of Study Area showing recommended improvements
6-2 | P a g e
Section B3: Stafford Junction