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    INTRODUCTION

    GENERAL

    Phenominal growth of motor vehicles in Indian cities has been

    creating enormous stress particularly at intersections. Major road

    junctions suffer from inadequate and inefficient traffic control system

    which invariably results increased delay and road accidents. Due to

    increase in delay and congestion at most of the intersections there hasbeen a great loss to the society in terms of time loss in waiting at the

    intersections and the excess fuel consumed by motorized vehicles.

    Therefore there is an alternative need to look for an efficient

    alternative solution to the existing problem to ensure more efficient

    and less expensive travel both for the present and future traffic.

    A possible remedy is to separate the grades of the intersecting

    roads in the form of grade separated intersections. In developing

    countries grade separation is adopted successfully to control and

    reduce traffic congestion and accidents at intersections.

    Grade separation is essential for managing traffic at major

    intersections. In big cities, this type of intersection causes least delay

    and hazard to the crossing traffic and in general is much superior to at

    grade intersections from the point of view of traffic safety and efficient

    operation. It eliminates all crossing conflicts at the intersection. There

    are two types of grade separated intersection with interchange and

    without interchange. Interchange is a system where by facility is

    provided for the movement of traffic between two or more roadways at

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    different levels in the grade separated junction. A structure without an

    interchange is an over bridge or underpass or grade separator whereby

    traffic at different levels moves separately.

    NEED FOR THE STUDY

    Grade separation is the highest form of intersection treatment.

    The code for grade separator design practiced in our country is for

    homogeneous traffic system, but the traffic system prevailing in our

    country is heterogeneous. Hence the code has to be evaluated

    whether it suits for Indian traffic flow.

    Certain geometric standards like acceleration and deceleration

    lane, ramp, gradient, distance between two grade separators need to

    be studied, analyzed and compared with standards.

    Along a major corridor many intersections are present and grade

    separator is constructed at a major intersection to avoid congestion.

    The congestion avoided in the major intersection moves to the next

    minor intersection present along the corridor. Hence grade separator

    constructed at the major intersection may not serve its purpose. Hence

    the form, shape of the grade separator and the topography and

    geometry of the area should be analyzed before construction of grade

    separator.

    Grade separators have to be evaluated to check whether the

    deceleration lane is within the standards and whether it is possible to

    reach a safe speed before reaching an intersection, as otherwise it

    may lead to accident. If the ramp gradient provided is more or the

    acceleration lane is less then it may cause difficulty for vehicles to

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    climb up. The safe distance between two grade separators has to be

    evaluated or otherwise it may lead to ride with roller coaster effect.

    OBJECTIVES

    The objectives of the study are the following

    To study the traffic characteristics, traffic movement, accident

    history

    To compute the benefits of reduction in delay and accident and

    To evaluate performance of existing grade separation facility

    STUDY METHODOLOGY

    Need for the Study

    Formulation of Objectives

    Literature Review

    Identification of Grade Separated

    Intersections

    for Study

    Data Collection

    Performance Evaluation of Grade

    Secondary

    Survey

    Accident andtrafficcomposition data(3 years before

    Primary Survey

    Traffic volumecount andComposition

    Speed

    Delay

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    STUDY AREA (I)

    STUDY INTERSECTIONS

    The study intersections are selected in Chennai city area. Five grade separated

    intersections are selected based on the form and shape as follows

    IIT Intersection

    Royapettah New college Intersection Royapettah G.H Intersection

    T.T.K Road Intersection.

    Data Analysis and Findings

    Comparison with IRC Standards

    Evaluation, Recommendations

    and Conclusion

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    Estimation of Delay cost

    Delay is a common phenomenon occurring at signalized

    intersection. Seldom one passes through all the intersections without

    delay of atleast few seconds. Delay at a signalized intersection means,the average delay caused to the vehicles at the signal due to various

    factors like traffic flow characteristics, vehicle type, timing of signal

    phases and cycle length. Delay is estimated in this study using three

    methods namely manual stopped vehicle count method, Websters

    model and TRANSYT12 for the non peak hour and the best among the

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    three methods is selected. For the peak hour delay is estimated using

    Websters model and TRANSYT12

    3 Estimation of Fuel cost

    The queue length occurring at the intersection and the average

    speed of vehicles in the queue was observed. Substituting the speed and

    distance in TRRL fuel consumption equation for two wheeler, car (old &

    new), bus and auto rickshaw (Eq 3 to Eq 7).

    Two wheeler = (3.38+ (549.57/Speed) +

    (0.00436*speed*speed))*distance -- (3)

    New Car = (21.85+(504.15/Speed)

    +(0.004957*speed*speed))*distance -- (4)

    Old car = (10.31+(1675.52/speed)+(0.0133*speed*speed))*distance

    -- (5)

    Bus = (32.97+ (3904.64/speed)+(0.0207*speed*speed))* distance

    -- (6)

    Auto = 2*((3.38+ (549.57/speed)+(0.00436*speed*speed))*distance)

    -- (7)

    The fuel consumed per hour for various categories of vehicles

    was found and multiplying it with present fuel price and delay per hour

    for various categories of vehicles, the total fuel cost consumed was

    arrived. The fuel cost was estimated for the complete year assuming

    conditions similar to peak hour will be prevailing for 6 hrs in a day and

    for 5 working days in a week.

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    4. Compilation of Accident Data

    Accident data was collected for 3 years before and after construction of grade separator.

    Accident data was collected such that it has different types of accident data like fatal, grievous,

    simple injury and no injury. Accident data for the study intersections was collected from Chennai

    City Traffic Police.

    5. IIT INTERSECTION

    IIT intersection grade separator was constructed in the year 2000 with a cost of 7

    crores. The length of the grade separator is 511 m. IIT intersection is a T-junction with the

    grade separator segregating the straight traffic flow. Traffic flow is one way, from Raj Bhavan

    towards Madhya Kailash. Volume count survey was done at the

    intersection. The Fig 4.1 shows the arm wise flow at IIT Junction.

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    Fig 4.1 Arm Wise Flow at IIT Intersection

    The total peak hour flow at the intersection was 13535 Pcu

    per hour. The peak hour volume flow through the grade separator was

    1741 Pcu per hour.

    Table 4.2 Delay Estimation before Construction

    of IITGrade Separator

    Capacity Analysis

    Easte

    rn

    Arm

    Weste

    rn

    Arm

    Northern

    Arm

    Adjusted flow rate, v (Pcu/hr) 5056 5093 2212

    Timing

    G 41 41 26

    Y 4 4 4

    Width of approach road 10.5 10.5 7

    Saturation flow rate, s (Pcu/hr) 5513 5513 3675

    v/c ratio arm wise 2.68 2.70 2.78

    Delay in Sec/Pcu using

    Websters 313 341 92

    Delay in Sec/Pcu using

    TRANSYT12 147 156 99

    Table 4.3 Delay Estimation after Construction of

    IIT Grade Separator

    Capacity Analysis Eastern Arm Wester Northern

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    n Arm Arm

    Phase I Phase II

    Straig

    ht

    Right Right

    and

    Left

    Right and

    Left

    Adjusted flow rate, v

    (Pcu/hr)

    3485 1782 1398 2999

    v/c ratio, X 1.33 1.90 2.66 3.31

    Delay in Sec/Pcu

    using WebstersModel

    119 151 102 231

    Delay in Sec/Pcu

    using TRANSYT12

    43 93 110 138

    Table 4.8 Accidents Occurrence at IIT Intersection before andafter Construction of Grade Separator

    Type ofAccident

    No. of Accidents

    During (1996-

    1999)

    before

    construction

    During (2001-2004) after

    construction

    Fatal 6 3

    Grievous 26 19

    Simple 25 19

    Non-Injury 3 3

    Total 60 44

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    Source: Chennai City Traffic Police

    The total cost of delay and fuel cost before construction of IIT

    grade separator was 367 Lakhs per year (Delay cost - 345 Lakhs, Fuel

    cost 22 Lakhs). The total cost of delay and fuel cost after construction

    of grade separator was 179 Lakhs per year (Delay cost - 173 Lakhs, Fuel

    cost - 6 Lakhs).The savings was 188 Lakhs per year.

    6. ROYAPETTAH G.H JUNCTION

    Royapettah G.H junctiongrade separator was constructed in the year 2000 with a cost

    of 8.5 crores. The length of the grade separator is 540 m. It is a four arm intersection with the

    grade separator segregating the straight traffic flow. Traffic flow is two way.

    The total peak hour flow at the intersection was 6733 Pcu

    per hour. The peak hour volume flow through the grade separator was

    1070 Pcu per hour. Arm wise flow at intersection is as shown in Fig.

    4.3.

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    Table 4.4 Delay Estimation before Construction

    of Royapettah G.H junction Grade Separator

    Capacity Analysis EB WB SB NB

    Adjusted flow rate, v

    (Pcu/hr)

    199

    31957

    135

    4

    161

    6

    v/c ratio, X 1.40 1.38 1.27 1.51

    Delay in Sec/Pcu using

    Websters Model67 66 67 71

    Delay in Sec/Pcu using

    TRANSYT12

    92 79 72 118

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    Table 4.5 Delay Estimation after Construction of RoyapettahG.H junction Grade Separator

    Capacity Analysis EB WB SB NB

    Adjusted flow rate, v

    (Pcu/hr) 744 996211

    7

    187

    3

    v/c ratio, X 0.73 0.97 1.49 1.32

    Delay in Sec/Pcu using

    Websters Model 54 51 63 58

    Delay in Sec/Pcu using

    TRANSYT1254 57 84 71

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    Table 4.9 Accidents comparison before and after construction

    of grade separator at Royapettah G.H junction

    Source: Chennai City Traffic Police

    The total cost of delay and fuel cost before construction of Royapettah G.H junction grade

    separator was120 Lakhs per year (Delay cost 112 Lakhs, Fuel cost 8 Lakhs). The total cost of

    delay and fuel cost after construction of grade separator was 83 Lakhs per year (Delay cost 80

    Lakhs, Fuel cost -3 Lakhs). The savings was 37 Lakhs per year.

    Type of

    Accident

    No. of Accidents

    During (1996-1999)

    before

    construction

    During (2001-

    2004) after

    construction

    Fatal 6 3

    Grievous 21 12

    Simple 21 18

    Non-Injury 2 0

    Total 50 33

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    7. ROYAPETTAH NEW COLLEGE JUNCTION

    Royapettah New college junction grade separator was constructed in the year 2000 witha cost of 8.5 crores. The length of the grade separator is 502 m. It is a four arm intersection with

    the grade separator segregating the straight traffic flow. Traffic flow is one way from Royapettah

    G.H towards New College

    The total peak hour flow at the intersection was 5184 Pcu per hour. The peak hour

    volume flow through the grade separator was 834 Pcu per hour. Arm wise flow at intersection is

    as shown in Fig 4.5.

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    Table 4.10 Accidents comparison before and after construction

    of grade separator at Royapettah New college junction

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    Source: Chennai City Traffic Police

    Type of

    Accident

    No. of Accidents

    During (1996-

    1999)

    before

    construction

    During (2001-

    2004) after

    construction

    Fatal 6 4

    Grievous 24 13

    Simple 28 14

    Non-Injury 4 1

    Total 62 32

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    8. TTK ROAD JUNCTION

    TTK road junction grade separator was constructed in the year 2000 with a cost of 10

    crores. The length of the grade separator is 610 m with two four arm intersection namely TTK

    road, C.P Ramaswamy road and Eldams road junction and TTK road and Luz Church road

    junction with the grade separator segregating the straight traffic flow from TTK road to C.P

    Ramaswamy road. Traffic flow is one way through the grade separator

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    Volume count survey was done at the intersection. The peak hour flow at the

    intersection was found. The total peak hour flow through TTK road and Luz Church road

    intersection was 5076 Pcu per hour. At TTK road, C.P Ramaswamy road and Eldams road

    junction was 6609 Pcu per hour. The peak hour volume flow through the grade separator was

    2355 Pcu per hour. Flow through grade separator is one way from TTK road to C.P Ramaswamy

    road. Arm wise flow at intersection is as shown in Fig 4.7.

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    Table 4.6 Delay Estimation before Construction

    of TTK road Grade Separator

    Table 4.7 Delay Estimation after Construction

    of TTK road Grade Separator

    Capacity Analysis

    TTK road, C.P

    Ramaswamy road

    and Eldams road

    junction

    TTK road and Luz

    Church road

    junction

    EB WB SB NB SB EB NB

    Adjusted flow rate, v

    (Pcu/hr) 20

    5497

    419

    3

    298

    5

    171

    4

    136

    2

    235

    5

    Delay in Sec/ PCU

    using TRANSYT1270 65 76 78 86 69 48

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    Table 4.11 Accidents comparison before and after construction

    of grade separator at TTK Road junction

    Source: Chennai City Traffic Police

    Capacity Analysis

    TTK road, C.P

    Ramaswamy road and

    Eldams road junction

    TTK road and

    Luz Church

    road junction

    EB WB SB NB SB EB

    Adjusted flow rate, v

    (Pcu/hr) 205 497 4193 825 1714 1362

    Delay in Sec/ PCU using

    TRANSYT1252 58 72 59 36 40

    Type of

    Accident

    No. of Accidents

    During (1996-

    1999)

    before

    construction

    During (2001-

    2004) after

    construction

    Fatal 4 6

    Grievous 30 19

    Simple 28 14

    Non-Injury 3 2

    Total 65 41

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    The total cost of delay and fuel cost before construction of TTK road

    junction grade separator at TTK road and Luz Church road junction

    without grade separator is 79 Lakhs per year (Delay cost 74 Lakhs,

    Fuel cost 5 Lakhs) and at TTK road, C.P Ramaswamy road and Eldamsroad junction was 123 Lakhs per year (Delay cost 115 Lakhs, Fuel cost

    -8 Lakhs). The total cost of delay and fuel cost after construction of

    grade separator at TTK road and Luz Church road junction was 28 Lakhs

    per year (Delay cost 23 Lakhs, Fuel cost 2 Lakhs) and at TTK road,

    C.P Ramaswamy road and Eldams road junction was 81 Lakhs per year

    (Delay cost 78 Lakhs, Fuel cost -3 Lakhs). The savings was 98 Lakhs

    per year.

    9. Conclusion

    The savings in delay and fuel cost after construction of IIT junction

    grade separator was 188 Lakhs per year.

    The 21% reduction in accident was observed at IIT junction after

    construction of grade separator.

    The savings in delay and fuel cost after construction of Royapettah

    G.H junction grade separator was 37 Lakhs per year.

    The 37 % reduction in accident was observed at Royapettah G.H

    junction after construction of grade separator.

    The savings in delay and fuel cost after construction of TTK road

    junction grade separator was 98 Lakhs per year The 32 % reduction in accident was observed at TTK road junction

    after construction of grade separator.

    In planning stage itself future modification in the grade separator

    should be considered.

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