Capacity Analysis of Un-signalized Intersection: A Case Study of City Junction

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Capacity Analysis of Un-signalized Intersection: A Case Study of City Junction

Amaranatha G A

Assistant Professor Civil Engineering

NCET

Bengaluru, India

Manjunatha N Assistant Professor Civil Engineering SJCIT

Bengaluru, India

K Sanjay Bargav Reddy

Civil Engineering NCET

Bengaluru, India

Abstract – Traffic flow on National Highway is obstructed by cross traffic from minor roads causing conflicts to vehicular and pedestrian flow. This leads to congestion, delay, accidents, increase in Vehicle Operating cost and decrease in capacity of the intersection. The present study is on intersection between Bangalore Mysore section of NH-275 and city. The existing T- junction subjecting to more conflicts because of heavy traffic flow on main road and more percentage of Multi Axle Trucks from Minor Road. Traffic volume survey was conducted for peak hours and same data has been analyzed in order to study various alternatives. Based on existing condition and topographical features suitable proposal like Interchange, Grade Separator, Roundabout and Ramps have been studied to propose best solution.

Key wordsGrade Separator, Interchange, VOC etc

  1. INTRODUCTION

    Indian metropolitan cities facing crisis of Urban Transportation. In spite of investing most of the countys budget on infrastructure, most of the roads are not successful in terms of safety especially at intersection. Congestion and accidents are the major problems on National Highway intersection, causing reduction in speed, delays, queuing of vehicles and pedestrians facing problem in crossing the Road. Improper geometrics and heavy traffic at intersection leads to poor traffic flow at intersection. At Intersections, since one flow is given priority over the right of way it is clear that the secondary or minor flow is usually seeking gaps. When flows are very light , which is in case on most urban and rural roads large gaps exit in the flows and thus few situation arises when vehicle arrive at uncontrolled intersection less than 10second or at interval close enough to cause conflicts. The T-junction between Bangalore Mysore and innovative film city junction subjected same problems mentioned above because of heavy traffic on National Highway and Multi Axle Traffic from Minor Road i.e. from innovative film city junction.

  2. TRAFFIC DATA ANALYSIS

    Classified Traffic volume: After studying traffic congestion at the site, classified traffic volume survey is carried out.

    Count. Data obtained after conducting traffic volume count for Morning peak hour from 7:00AM TO 11:00AM and Evening peak hours from 4:00pm to 8:00pm are shown in table below.

    Table 1: 8 Hours Traffic volume count

    From

    To

    Hourly Volume in Nos

    Hourly PCUs

    7:00

    8:00

    1679

    2348

    8:00

    9:00

    2425

    2856

    9:00

    10:00

    2026

    2429

    10:00

    11:00

    1853

    2198

    16:00

    17:00

    2489

    3069

    17:00

    18:00

    2634

    3165

    18:00

    19:00

    2423

    3008

    19:00

    20:00

    2188

    2504

    Total PCUs

    17717

    21577

      1. Classified Traffic Volume Count at the Junction

        In order to evaluate the proportion of each category of vehicle on particular direction, traffic volume count is analyzed and details of Peak Hour Traffic flow are presented in Table 2 and also flow Diagram.

        Table 2: Classified Peak Hour Traffic Volume Count

        Leg

        From D1

        From D2

        From D3

        Total Vehicles

        Total PCU's

        Direction

        D1 TO D2

        D1 TO D3

        D2 TO D1

        D2 TO D3

        D3 TO D1

        D3TO D2

        Cars/Jeeps

        140

        26

        595

        22

        112

        38

        933

        933

        Auto

        16

        12

        32

        26

        1

        34

        121

        121

        Mini Bus

        25

        8

        28

        6

        45

        9

        121

        182

        Bus

        73

        1

        72

        6

        31

        12

        195

        585

        LCV

        62

        23

        88

        6

        37

        8

        224

        336

        2 axle

        74

        6

        31

        0

        2

        2

        115

        345

        3 axle

        21

        9

        10

        1

        0

        2

        43

        129

        MAV

        5

        2

        6

        0

        3

        0

        16

        72

        2-Wheeler

        258

        44

        356

        52

        68

        79

        857

        429

        Total

        675

        131

        1225

        119

        300

        184

        2634

        3165

        *D1-Bangalore, D2-Mysore, D3-Innovative Film City

        Figure 1: Traffic Flow Diagram at the Junction

        Figure 1 Show directional flow of traffic , the traffic on major road is high as its 4lane road and peak hour traffic volume at this location is 3165 PCUs of which 3131 PCUs are fast moving vehicles and 34 PCUs are slow moving vehicles. The traffic on main road contributes about 72% and turning traffic is about 28%. From total turning traffic the proportion of goods vehicle is 13% which leads to major delay for main stream traffic.

      2. Capacity Analysis of Junction

        1. Directional Distribution of Traffic Volume at this Junction

          The traffic movement for 8hour duration at the junction is 17717 vehicles & 21577 PCUs and peak hour traffic

          Table 3: Directional Distribution presented at the junction are

          presented

          Leg

          From D1

          From D2

          From D3

          Direction

          D1 TO D2

          D1 TO D3

          D2 TO D1

          D2 TO D3

          D3 TO D1

          D3TO D2

          Type of Vehicle/PCU

          Car/jeep/vans

          21%

          20%

          49%

          18%

          37%

          21%

          Auto rickshaw

          2%

          9%

          3%

          22%

          0%

          18%

          Mini Bus

          4%

          6%

          2%

          5%

          15%

          5%

          Bus

          11%

          1%

          6%

          5%

          10%

          7%

          Light Commercial Vehicle/LCV

          9%

          18%

          7%

          5%

          12%

          4%

          2- Axle

          11%

          5%

          3%

          0%

          1%

          1%

          3-Axle

          3%

          7%

          1%

          1%

          0%

          1%

          Multi Axle

          1%

          2%

          0%

          0%

          1%

          0%

          Sccoter & Motor Cycle

          38%

          34%

          29%

          44%

          23%

          43%

          Pedal Cycle

          0%

          0%

          0%

          0%

          0%

          0%

          Cycle Rickshaw

          0%

          0%

          0%

          0%

          0%

          0%

          Horse Drawn Vehicle

          0%

          0%

          0%

          0%

          0%

          0%

          Bullock for Camel Drawn Vehicles

          0%

          0%

          0%

          0%

          0%

          0%

          Agricultural tractor

          0%

          0%

          0%

          0%

          0%

          0%

          Agricultural tractor with Trailer

          0%

          0%

          0%

          0%

          0%

          0%

          Others-Please Describe

          0%

          0%

          0%

          0%

          0%

          0%

          Total

          100%

          100%

          100%

          100%

          100%

          100%

          Directional Distribution of Traffic Mini Bus

          movement at the junctions is 2634 Vehicles & 3165 PCUs. Details of the Directional Distribution presented at the junction are presented in Table 3. below. Vehicle Composition diagram is presented in Figure 2 below.

          100%

          % of Vehicles

          50%

          Bus

          Multi Axle

          D1 TO D2

          D1 TO D3

          D2 TO D1

          D2 TO D3

          D3 TO D1

          D3TO D2

          0% 3 axle

          Direction of Traffic

    1. axle

    Figure 2: Vehicle Composition Diagram

    In order to find capacity of uncontrolled intersection following parameters are to be calculated

    1. Compute the critical Gap and follow up time for Right Turn from Minor Road.

      Critical Gap,

      tcx = tcb + tcHV. PHV + tcG. G tcT tLT

      Follow-Up time

      tfx = tfb + tfHV. PHV

      Where tcx is the Critical Gap for the movement x, tcb is the base critical gap, tcHV is the adjustment factor for heavy vehicles, PHV is the proportion of heavy vehicles, tcG is the adjustment factor for grade, G is the percentage grade, tLT is the critical gap adjustment factor for intersection geometry, tfx is the follow up time for minor movement x, tfb base follow up time.

      tcx = 6.9 + 2 0.07 + .2 0 0 0

      tcx = 7.2 Secs

      tfx = 3.37 Secs

      tcx and tfx are calculated by using data from Table 4 below

      Vehicle Movement

      Base Critical gap, tc

      Base Follow up

      4-Lane

      Time

      Right Turn from minor Road

      6.9

      3.3

      Adjustment to base Critical gap& follow up

      tcHV

      2

      Four Lane Major Road

      tcG

      1

      tcT

      0

      TLT

      0

      tfHV

      1

    2. Compute Conflicting flow Rate

    The traffic flow process at uncontrolled intersection is complicated since there are many distinct vehicular movements to be accounted for. These conflicts results in decreasing capacity, increasing delay and increasing potentials for traffic accidents.

    Conflict flow for Right Turn from Minor road can be estimated by using formula below

    e. Movement Capacity(Cm)

    Vehicles use gaps at a intersection in a prioritized manner. When traffic becomes congested in a high- priority movement, it can impede lower-priority movements. This impedance may come due to both pedestrians and vehicular sources called movement capacity. For present study we have not considered pedestrian crossing. The movement capacity for Right turn Traffic from minor can be obtained as

    = ()

    = 384 299

    =

    In order find the Level of Service for existing Intersection and traffic from minor Road to Major Road the table 5 gives various values.

    Table 5: Level of Service for Un-Signalized Intersection

    Level of Service for Un-Signalized Intersection

    Reserve Capacity

    Level of Service(LOS)

    Expected Delay to Minor Street Traffic

    >400

    A

    Little or No Delay

    399-300

    B

    Short Traffic Delays

    299-200

    C

    Average Traffic Delays

    199-100

    D

    Long Traffic Delays

    99-0

    E

    Very Long Traffic Delays

    F

    Stop and Start

    Source: IRC SP-41 Guidelines for Design of At-Grade Intersections

    From table 5 its concluded that the movement capacity for a traffic from Innovative film city merges with Bangalore direction with stop and start i.e. falls under Level of Service E.

  3. CONCLUSION

Above discussion shows that, because of heavy traffic flow on National Highway (NH 275), existing condition is not sufficient and some solution is required to reduce congestion at junction and for Right Turning Traffic from Innovative Film City. This is possible by providing either signal, flyover, under pass or Interchange. But as the main

stream traffic is high it will be very difficult to provide

1

= (1 3) + (1 2) + 2 3 2

underpass, during construction traffic diversion will be not be easy. Also traffic signal cannot be provided as it has very

1

= (131) + (675) + (119)

2

= 860 /

long Cycle time. Construction of flyover is very costly and there is a need to provide signal underneath, which causes delay and so should not be provided.

d. Determining Potential Capacity (Cp)

Potential Capacity is the Maximum Number of vehicles which can be accommodated under given condition with a reasonable expectation of occurrence. Once the conflicting volume ,critical gap and follow up time are known for a given movement its potential capacity can be estimated using graph given in IRC SP-41 pg 117 Figure III-2 and for existing condition the potential capacity (Cp) obtained is 90 PCUs per Hour. So actual capacity will be 299 PCUs per hour.

Thus, by providing separate Ramp could be the best option as the heavy traffic of National highway could be diverted under the rmp .Hence, chances of accidents, traffic jam could be considerably reduced, which would cause reduction of pollution. Also by considering future expansion of national highway, to make NH-275 as an expressway, Ramp will be best option.

REFERENCES

[1]

IRC: 92 (1985).Guidelines for the Design of Interchanges

Urban Areas.

in

[2]

IRC: 62 (1976).Guidelines for Control of Access of

Highways,

[3]

IRC. IRC: 86 (1983).Geometric Design Standards for

Urban

Roads in Plains, IRC.

[4]

IRC: SP: 16 (2004).Guidelines for Surface Evenness of

Highway Pavements (First Revision), IRC.

[5]

IRC: SP: 44 (1996). Highway Safety Code, IRC.

[6]

Justo CEG and Khanna SK (2012). Highway Engineering,

9 th

edition (Nem Chand and Bros, Roorkee).

[7]

IRC: 102-1988, Traffic Studies for Planning Bypasses

around Towns

  1. IRC: 64-1990, Guidelines for Capacity of Roads in urban Areas

  2. Dr. L.R. Kadyali. Traffic Engineering and Transportation Planning. Khanna Publishers, Seventh Edition 2007.

  3. IRC: 64:1990 Guidelines For Capacity of Roads In Rural Areas.

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