A Traffic Management Scheme to ease Vehicle & Pedestrian Movements in the Kottawa Town

: Among the suburban towns in Sri Lanka Kottawa can be considered as one that regularly faces many traffic related problems. It is observed that most of those who enter the town, face problems daily. In the case of drivers, their time is often wasted due to traffic congestion and in the case of pedestrians their safety is at risk due to the absence of a good traffic management system. Kottawa experiences severe traffic congestion because many motorists and pedestrians fail to follow the prevalent rules and because there is no proper traffic management scheme. There are three junctions in the town. Most of the motorists have to travel at least through two of these junctions. Therefore it could be seen that a considerable amount of vehicles frequently travel across the three junctions during peak hours. Southern Expressway users too travel through the Kottawa town since Makumbura interchange is situated next to Kottawa. At present, it is seen that most motorists including those who use the Southern Expressway waste their time at the Kottawa town. Stage 1of the Outer Circular Highway is now in operation and the other two stages will also be commissioned soon . Since they too will be starting from the Makumbura interchange, traffic in the town will increase further.


Introduction
Kottawa town is currently experiencing severe traffic congestion and many people who enter the town, appear to face problems such as waste of their time due to the traffic congestion and unsafe pedestrian movements. At the time of collecting the data for this study, the area under study had no proper traffic control system in operation. It was felt that a properly designed and signalized traffic control system might help to improve the road efficiency. Therefore in the absence of a proper traffic management scheme, this town gives rise to traffic blocks caused by the failure on the part of motorists and pedestrians to follow prevailing rules. The roads meeting at Kottawa are Colombo Awissawella Road (A4), Piliyandala Road (B239), Athurugiriya Road (B45), Battaramulla Road (B47) and a short stretch of a one-way road. As seen in Figure 1, there are three junctions in the Kottawa town. The Colombo-Awissawella Road (A4) and the Athurugiriya Road (B45) meet at one junction (3-way junction). The Colombo-Awissawella Road (A4), Piliyandala Road (B239) and a stretch of the one-way road meet at the second junction (4-way junction). The Battaramulla Road (B47), Athurugiriya Road (B45) and a stretch of the one-way road are meeting at the third junction which is also a four-way junction. Therefore, a considerable number of vehicles frequently travel across the three junctions during peak hours and also at certain other times. Some obvious problems seen at the Kottawa town area are the illegal constructions, street vendors conducting their businesses by roadsides causing obstruction, roadside parking for want of sufficient parking areas, pedestrians jay-walking on carriageways, the absence of proper bus parking arrangements etc. The aim of this study is to design a junction improvement plan for the Kottawa town to ensure a smoother traffic flow and to facilitate safer vehicular and pedestrian movements catering to the additional vehicular traffic that will result from the extension of the Southern Expressway and the Outer Circular Highway through the Makumbura interchange.
Those who use the Southern Expressway have to travel through the Kottawa town to reach the Makumbura interchange. This makes it difficult to avoid traffic congestion at Kottawa. Stage 1 of the Outer Circular Highway is currently in operation and once the other two stages are completed, they will add more traffic to the Makumbura interchange which will further worsen the situation. Through this study it is expected to offer solutions to improve pedestrian movements, vehicle movements, and vehicle parking facilities in the Kottawa town and improve overall safety which will help the road users to have greater mobility, shorter travel times and easy accessibility to the town.

Data Collection
The data that is already available was collected from the following organizations:

Identification of the Peak Hour
From the initial traffic counts, peak hours were identified as; the morning peak hour from 7:30hrs-8:30hrs, daytime peak hour from 12:30hrs-13:30hrs, and evening peak hour from 17:30hrs-18:30 hrs. Therefore turning movement data was taken by adding one hour before and after the pre-identified peak hours.

Capacity Analysis for Year 2014
In the area under study, there were three junctions with eight legs as shown in Figure 2.

Figure 2 -Capacity Analysis Road Sections
Road sections P1-P1, P2-P2 and P4-P4 along the Colombo-Awissawella Road had been considered as a multi-lane, and undivided suburban road. Others were considered as twoway, two-lane, rural roads. Different factors had to be taken into account under different conditions. The actual flow rate is satisfied for the year 2014. The width of the road was sufficient to accommodate peak hour traffic flow.

Calculation of the Allowable Flow of a Two Way-Two Lane-Rural Road
Considering the road section P3-P3 during the morning peak hour at LOS B: Results for the two-way, two-lane road during the morning peak hour and evening peak hour were calculated for different LOSs.

Capacity Condition during 2014
Analyzed results of the allowable and actual flows of the multilane and two-way, two-lane roads during the evening peak hour and morning peak hour were used to verify whether the capacity exceeded in 2014. According to the results, it can be seen that the capacity was fulfilled for a Level of Service D during both the morning peak hour and the evening peak hour during the year 2014. However the difference between the actual flow and the allowable flow was small. Therefore the actual flow will reach the allowable flow within the next few years. Considering the highest number of lanes of LOS D of each road section, the following conclusion was made.

Roundabout Analysis
As a solution for the identified problems, a signalized roundabout was proposed at Junction-3 and its design was carried-out [2].
The typical turning movement diagram is shown in Appendix A - Figure  Results obtained are tabulated in Table 2.

Table 2 -Maximum Entry Capacity
The allowable maximum capacity was greater than the actual entry flow at all of the approaches. Therefore, the overall roundabout capacity will not be exceeded. Hence the pedestrian crossing may be allowed.

Delay Analysis of the Roundabout
The circulating flow and entry flows were used to calculate the queuing delay at each approach.
Results are shown in Table 3.

Turning Path Radius of the Island Arrangement
To determine the island radius, the average speed was assumed as 30 km/hr. Using the AUSTROADS guidelines [8], island radius was taken as 43.8 m

Delay due to Speed Variation
Spot speed data was collected and statistically analysed to identify the speed profiles at six selected points.  It can be seen that the speed first decreased from point 1 to point 2 and increased thereafter under steady flow in both directions. The maximum speed was 34 km/h in Awissawella-Colombo direction in the morning and 26 km/h in the opposite direction in the morning at Point 2. The lowest maximum speed in the Colombo-Awissawella direction was in the morning.

Delay experienced by Expressway Users
The time taken to travel between three identified points P1, P2 & P3 in the Awissawella-Colombo direction was noted and the travel times between the points P4, P5 & P6 in the opposite direction were recorded using a car. The average of the five trips in one direction during the morning peak hour, day time peak hour, evening peak hour and also during two off peak hours was computed. The distances between any two points were also recorded. The average journey times so computed are shown in Table 4. From Table 4, it is seen that the motorists take a longer time to travel from P4 to P5 (coming from the direction of Colombo)during evening peak hour and that during morning peak hour a longer time is taken to travel from P1 to P2 in the opposite direction (coming from the direction of Avissawella). Therefore in these sections, delays occurred and a solution will be needed to minimize travel time.

Distribution of Accidents
Data under the categories of Fatal, Grievous and Minor (or Light) injuries and related to accidents that occurred during the last ten years is shown graphically in Figure 8. Accident data was used to identify black spots and in the design layout. Steps were taken to eliminate negative effects of blackspots.

Black Spot Identification
Locations where three or more accidents had occurred during the last ten years were considered as blackspots [3]. The aim was to reduce the number of accidents at these identified blackspots.
The accident records was used to study in detail the causes of accidents; types of vehicles involved, time of the accidents, collision types, types of injuries or damages etc. The collision diagram developed for the past ten years considering this data is shown in Appendix B- Figure B1.

Pedestrian Analysis -Side Walk Analysis
It is observed that most pedestrians walk along the right or the left side of the footpath of Awissawella -Colombo (A04) approach. The total number of pedestrians walking past (in both directions) at a certain point was counted at 15 minute intervals during peak time.

Level of Service to Pedestrians in 2014
The total walkway width is 2.0m (including electricity poles and waste bins).
Assumptions:  15 min peak flow rate is 180 p/15-min on the left side  15 min peak flow rate is 175p/15-min on the right side  Obstacles -Electricity poles, waste bins etc. At LOS D, a very slow pedestrian movement touching each other is possible. Long-term durations at this density will not be comfortable.

3.19
Forecast of the Side Walk Pedestrian Numbers for 2034 Pedestrian growth rate in the Colombo District was taken as 0.35% based on the statistics of the last census done. Number of pedestrians after a period of n years = Number of pedestrians in 2014×(1+ Growth percent) n It was presumed that the maximum number of pedestrians on the left hand side is 180 and that it is 175on the right hand side.

Cross Walk Analysis
There were four zebra crossings in the town as shown in the Figure 9. Pedestrians walking in both directions were counted at each crossing at fifteen minute intervals on a week day. Data was collected from 7:00 -9:00hrs,12:30-14:30hrs, and from 17:00-19:00 hrs.

Figure 9 -Locations of Pedestrian Crossings
The number of pedestrians walking past each crossing during morning, day time and evening peak hour is plotted in Figure10.

Identification of Peak Pedestrian Count at the four Zebra Crossings
In the morning, the number of pedestrians walking across the crossings was counted at fifteen minute intervals from 7:00 -9:00hrs and from 17:00 -19:00 hrs in the evening. The results are tabulated below. The highest pedestrian number is underlined (see Table 9) by comparing the morning and evening counts at each crossing. These highest values were used to analyse each pedestrian crossing. Results are graphically shown below.

Forecast of Crosswalk Pedestrians for 2034
Based on the statistics, the pedestrian growth rate was taken as 0.35%. Results are shown in Table 10.

Calculation of the Cross Walk Width for 2034
A pedestrian LOS D was considered as satisfactory for the year 2034 at the peak pedestrian flow. Hence pedestrian space was taken as 2.4 ft 2 /person.
Design width (ft)=(Pedestrian space × Pedestrian per min× cycle time)/Crossing length As the shifting of the bus stand to a new location has been proposed, it is assumed that the number of pedestrians at the pedestrian crossing at P3+P4 will be reduced. Existing pedestrian crossings P1+P2, P5+P6 and P7+P8 will be shifted to three signalized intersections.
The new crossing arrangement is indicated in the proposed layout plan.

Vehicle Parking
There is a block of government owned land closer to Junction 2 in the Kottawa town and adjoining the Awissawella -Colombo Road and Piliyandala Road. This place is the most suitable location to provide for car parking. The extent of this block of land is about 121m x 84m.

Off-Street Parking Layout
Considering the fact that there is not much land available in the Kottawa town, a multi storied car parking layoutwith split level car parking is proposed [4], [5]. The proposed off-street three story car park arrangement is given in Figure 13.

Bus Bay and Bus Parking Area
The area occupied by the present bus stand has not been planned properly and the accident studies reveal that a large number of accidents occur in this area. This highlights the need to plan properly bus loading and unloading. Considering the land size and parking demand of buses, a properly designed bus bay would minimize the risk the pedestrians would face when they embark and disembark busses.

Proposed Traffic Signal System
A number of phases have been selected considering the traffic volume of each road at the intersection. When Kottawa town as a whole is considered, there is Colombo -Awissawella Road intersecting with roads leading to Piliyandala, Athurugiriya and Battaramulla. During morning and evening peak hours, traffic flows along the Colombo and Awissawela approaches are more than the flows of any other approach. The following three phases were selected as the most suitable phases for the Kottawa intersection to minimize delays and queue values after giving due priority to the Colombo and Awissawella approaches.

Figure 14 -Proposed Traffic Signal System (three phases)
The forecasted values for the next twenty years were converted to passenger car units (PCU) and that data was used for the signal design and the following section shows the specimen calculations and the results. When the signal phasing and timing are fixed for peak flows in 2034,the timing could be adjusted rather easily to suit present flow conditions. Furthermore, this signal timing has to be adjusted from time to time as the flow conditions change or upgraded for a flow actuated system.

Morning Peak Hour
The lane width is considered as 3.7m and site factor as 100% (between 85% for a poor site and 120% for a good site) with no gradient. For turning lanes, turning radius is to be taken as 15m . Step 3 -Site Factor and Gradient Saturation flow does not change with the site factor and gradient, because the site factor is taken as 100% and there is no gradient in the study area.
Step Step 5-Revised Design Flow In this step, only Flow 12 changes, because Flow 12 can be allowed to move during the two phases and the revised design flow is obtained from the design flow divided by 2. Revised design flow 12 = 814/2 = 407 pcu Step 8 -Practical "y" Values When the three junctions are considered together, the actual design flows are found to be greater than the saturation flows given by the number of lanes and lane widths. As a result of this, in some flows, q/S ratio (y) is greater than 1. The result shows that it is not possible to discharge a whole number of vehicles within one signal cycle. During the selected cycle time, the volume of discharge can be calculated from the design peak hour volume. Then the "y" value has to be calculated again. Using the new "y" value, calculate Y and green time for each phase.
Step  Step 10-Delay Calculation Delay can be calculated as follows for Phase 1.  The minimum delay is observed in Phase 3 and this means that in Phase 3, the time for which the motorists have to wait before they can depart through the intersection is minimum. In Phase 2, the time that the motorists have to wait for travel through the intersection is maximum.
Step 11-Calculation of the Average Queue

Channelization
Channelization simplifies the traffic flow by restricting the driver's choice, reducing conflict points, segregating conflicting flows, guiding traffic into suitable paths, and reducing the area of conflicts by controlling the intersecting traffic streams. Channelization protects pedestrians from turning vehicles by providing pedestrian refuges and discouraging prohibited or undesirable movements of motorists.
A centre median along the A4 Road with semicircular end shapes was proposed for the Kottawa town to separate out the opposing traffic at the traffic signal and at the roundabout. The length of the centre median was taken to suit the site conditions.
Minimum width of centre median -1.2 m. Radius of the semi-circular end -0.6 m.
The proposed centre median is indicated in the final layout plan given in Appendix C - Figure  C1.

Conclusion
From the capacity analysis results, it was seen that a signalized roundabout at the third junction [i.e. the four-way junction where the Battaramulla Road (B47) and the Athurugiriya Road (B45) cross each other] and at the other two intersections was necessary and it was appropriate to have traffic signals at these places.
Thus designs were carried out accordingly. Cross-walk and side walk designs were done to improve the pedestrian facilities. A suitable parking area was proposed separately for the vehicles and busses. In addition to this, bus bays for loading and unloading pedestrians, suitable channelization turning regulations, and hand railings were proposed. Finally, a suitable layout plan was drawn based on the results of the analysis and designs.
From the road capacity checks performed on different road sections in the Kottawa town, it was found that some road sections could not handle traffic flows during peak hours even as at now and that the other sections also would face the same situation in 20 years time from now (i.e. 2034), unless improvements are carried-out. Hence to cater to the 2034 traffic flows, the following numbers of lanes are proposed for the sections (see Table 16).
In addition to the traffic growth in the surrounding roads, additional vehicular traffic that will generate in future from the Southern Expressway expansion and Outer Circular Highway through the Makumbura interchange has been taken into account. To cater to the heavy traffic during peak hours, a traffic signal system linking the three junctions was designed. At Junction 3, a signalised roundabout with a center-island (7.75m radius)was proposed. A centre median along A4 with semi-circular end shapes was also proposed for the Kottawa town to separate the opposing traffic through the traffic signal and the roundabout.
The present bus stand has not been properly planned and it does not have passenger shelters and queuing facilities. Therefore passengers face difficulties when busses turn within the area forcing them to move away from their standing positions to give-way for the turning busses and this causes them great inconvenience. Hence to minimize this bus parking problem, it is proposed that there should be forty slots with parking facilities and two bus bays for the Awissawella route and Colombo route which can load concurrently two buses going in the same direction.
Currently there are many shops within the town area and customers park their vehicles in an undisciplined manner. According to accident reports, vehicles had collided with parked vehicles at identified parking places due to irregular parking. Some shops have provided unplanned parking areas and as a result of this, customers use sidewalks for parking their vehicles. Vehicles and pedestrians face difficulties as a result of this practice. Hence a comprehensive parking demand survey was carried-out in the town area and considering the results of questionnaire surveys, a split level four storied car park was proposed, with each story with adjacent parking levels separated by a half story height. The car park that was designed was of 85.0 m x 33.6 m in size and it could accommodate 240 vehicles for parking at a time.
In addition to those solutions, to segregate pedestrians and vehicles and minimise j-walking pedestrians, hand rails in town area were proposed. In addition, to reduce conflicting movements of traffic flows, left turning regulation for Athurugiriya Road section at Junction 1was proposed. The authors believe that these solutions would minimize the delays experienced by the expressway users in the Kottawa town and provide a safe and efficient movement for vehicles and pedestrians along the roads in the town.