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SIGNALISED INTERSECTIONS

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Title: SIGNALISED INTERSECTIONS


1
SIGNALISED INTERSECTIONS
  • TS4273 Traffic Engineering

2
First Traffic Light
  • Traffic lights were used before the advent of the
    motorcar. In 1868, British railroad signal
    engineer J P Knight invented the first traffic
    light, a lantern with red and green signals.
  • It was installed at the intersection of George
    and Bridge Streets in front of the British House
    of Commons to control the flow of horse buggies
    and pedestrians.

http//www.didyouknow.cd/trafficlights.htm
3
Prinsip-prinsip desain simpang bersinyal
  • Suatu persimpangan membutuhkan lampu lalulintas
    jika waktu tunggu rata-rata kendaraan sudah lebih
    besar daripada waktu tunggu rata-rata kendaraan
    pada persimpangan dengan lampu lalulintas.

4
Prinsip-prinsip desain simpang bersinyal
  • Waktu tunggu rata-rata kendaraan pada
    persimpangan bersinyal dipengaruhi oleh
  • Arus lalulintas pada masing-masing arah,
  • Waktu antara kedatangan kendaraan dari
    masing-masing arah,
  • Keberanian pengemudi untuk menerima waktu antara
    yang tersedia guna menyeberangi jalan.

5
Prinsip-prinsip desain simpang bersinyal
6
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7
Scope of IHCMSignalised Intersection Analyses
  • Isolated, fixed-time controlled signalised
    intersections with normal geometry layout
    (four-arm and three-arm) and traffic signal
    control devices.
  • Coordinated traffic signal control is normally
    needed if the distance to adjacent signalised
    intersections is small (lt 200m). ? Persimpangan
    Raya Darmo Polisi Istimewa Raya Darmo RA
    Kartini.

8
Objectives of IHCMSignalised Intersection
Analyses
  • To avoid blockage of an intersection by
    conflicting traffic streams, thus guaranteeing
    that a certain capacity can be maintained even
    during peak traffic conditions

9
Objectives of IHCMSignalised Intersection
Analyses
  • To facilitate the crossing of a major road by
    vehicles and/or pedestrians from a minor road
  • To reduce the number of traffic accidents caused
    by collisions between vehicles in conflicting
    directions.

10
Potential Conflict at Intersections
11
Primary and Secondary Conflictis in a Four-Arm
Signalised Intersections
12
Time Sequence for Two-Phase Signal Control
13
Time Sequence for Four-Phase Signal Control
14
Time Sequence for Two-Phase Signal Control
15
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16
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17
Purpose of the Intergreen Period
  • Warn discharging traffic that the phase is
    terminated. ? Amber Period (for urban traffic
    signal in Indonesia is normally 3,0 sec)
  • Certify that the last vehicle in the green phase
    which is being terminated receives adequate time
    to evacuate the conflict zone before the first
    advancing vehicle in the next phase enters the
    same area. ? All-Red Period

18
Signal Phasing Arrangements
  • Introducing more than two phases normally leads
    to an increase of the cycle time and of the ratio
    of time allocated to switching between phases
    (especially for isolated and fixed-controlled).

19
Signal Phasing Arrangements
  • Although this may be beneficial from the traffic
    safety point of view, it normally means that the
    overall capacity of the intersection is
    decreased.

20
Basic Model for Saturation Flow (Akcelik 1989)
21
Basic Model Saturation Flow
  • Discharge rate starts from 0 at the beginning of
    green and reaches its peak value after 10-15 sec
  • Effective Green Displayed Green Time Start
    Loss End Gain
  • Start loss ? End gain ? 4,8 sec (MKJI p.2-12)
  • Effective Green Displayed Green Time

22
Basic Model Saturation Flow
  • Base saturation flow is different between
    Protected approach and Opposed approach
  • For protected approach ? S0 600 x We
  • For opposed approach ? S0 in Indonesia usually
    lower where there is a high ratio of right
    turning movements, compare with Western models.

23
Perhitungan Arus Jenuh Metode Time Slice
  • Arus jenuh/jam ? (3.600/5)x4,5 3.240 smp/jam
  • Jika lebar lajur 4,0m ? (3.240/4) 810
    smp/jam/m
  • Maka ? S 810 x We

24
Traffic Safety Considerations
  • Traffic accident rate for signalised
    intersections has been estimated as 0,43
    accidents/million incoming vehicles as compare to
    0,60 for unsignalised intersections and 0,30 for
    roundabouts.

25
STEP A-1 Geometric, Traffic Control and
Environmental Conditions
  • General information (date, handled by, city,
    etc.)
  • City size (to the nearest 0,1 M inhabitants)
  • Signal phasing timing
  • Left turn on red (LTOR)
  • Approach code
  • Road environment and level of side friction
  • Median
  • Gradient
  • Approach width (to the nearest tenth of a meter)

26
Geometry of Signalised Intersection
27
STEP A-2 Traffic Flow Conditions
Vehicle Type pce for Approach Type pce for Approach Type
Vehicle Type Protected Opposed
Light Vehicle (LV) 1,0 1,0
Heavy Vehicle (HV) 1,3 1,3
Motorcycle (MC) 0,2 0,4
Q QLV (QHV x pceHV) (QMC x pceMC)
28
STEP B-1 Signal Phasing and Timing
  • If the number and types of signal phases are not
    known, two-phase control should be used as a base
    case.
  • Separate control of right-turning movements
    should normally only be considered if a
    turning-movement exceeds 200 pcu/h and has a
    separate lane.

29
STEP B-1 Signal Phasing and Timing
  • Early start leading green ? one approach is
    given a short period before the start of the
    green also in the opposing direction (usually
    25-33 from total green time)
  • Late cut-off lagging green ? the green light in
    one approach is extended a short period after the
    end of green in the opposing direction.
  • The length of the leading and the lagging green
    should not be shorter than 10 sec.

30
STEP B-2 Intergreen time and lost time
Intersection Size Mean Road Width Intergreen Time Default Values
Small 6 9 m 4 sec/phase
Medium 10 14 m 5 sec/phase
Large 15 m 6 sec/phase
Only for planning purposes !!!
31
STEP B-2 Intergreen time and lost time
For operational and design analysis !!!
  • LEV, LAV ? distance from stop line to conflict
    point for evacuating and advancing vehicle (m)
  • lEV ? length of evacuating vehicle (m)
  • VEV, VAV ? speed of evacuating and advancing
    vehicle (m/sec)

32
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33
STEP B-2 Intergreen time and lost time
  • VAV ? 10m/sec (motor vehicles)
  • VEV ? 10m/sec (motor vehicles)
  • VEV ? 3m/sec (un-motorised)
  • VEV ? 1,2m/sec (pedestrians)
  • lEV ? 5m (LV or HV)
  • lEV ? 2m (MC or UM)

34
STEP B-2 Intergreen time and lost time
  • IG ? Intergreen Allred Amber
  • The length of AMBER usually 3,0 sec

35
STEP C-1 Approach Type
  • PROTECTED (P) ? Discharge without any conflict
    between right-turning movements and
    straight-through/left-turning movements.

36
STEP C-1 Approach Type
  • OPPOSED (O) ? Discharge with conflict between
    right-turning movements and straight-through/left-
    turning movements from different approaches with
    green in the same phase.

37
STEP C-2 Effective Aproach Width (We)
  • Without LTOR
  • For Approach Type P (Q QST)
  • If WEXIT ? We x (1 - pRT - pLT)
  • ? We WEXIT

38
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39
STEP C-2 Effective Aproach Width (We)
  • If WLTOR 2m (it is assumed that the LTOR
    vehicle can bypass the other vehicle)
  • ? We min (WA-WLTOR) , (WENTRY)
  • For Approach Type P (Q QST)
  • If WEXIT lt We x (1 pRT)
  • ? We WEXIT

40
STEP C-2 Effective Aproach Width (We)
  • If WLTOR lt 2m (it is assumed that the LTOR
    vehicle cannot bypass the other vehicle)
  • ? We min (WA) , (WENTRYWLTOR) ,
  • (Wax(1pLTOR)-WLTOR)
  • For Approach Type P (Q QST)
  • If WEXIT lt We x (1 pRT pLTOR)
  • ? We WEXIT

41
STEP C-3 Base Saturation Flow (S)
  • For protected approach

42
STEP C-3 Base Saturation Flow (S)
  • For Approach Type P
  • S0 ? base saturation flow (pcu/hg)
  • We ? effective width (m)
  • Figure C-31 page 2-49

43
STEP C-3 Base Saturation Flow (S)
  • For Approach Type O (opposed)
  • QRT and QRTO (Column 14 Form SIG-II opposed
    discharge right-turning)
  • Figure C-32 page 2-51 for approaches without
    separate right-turning.
  • Figure C-33 page 2-52 for approaches with
    separate right-turning.
  • Use interpolation if approach width larger or
    smaller than actual We

44
STEP C-3 Base Saturation Flow (S)
  • Ex without separate right-turning lane
  • QRT 125 pcu/h, QRTO 100 pcu/h
  • Actual We 5,4m
  • Obtain from Figure C-32 p. 2-51 (We5 We6)
    S6,0 3.000 (pcu/hg) S5,0 2.440 (pcu/hg)
  • Calculate
  • S5,4 (5,4-5,0)x(S6,0 - S5,0) S5,0
  • 0,4(3.000-2.440)2.440 ? 2.660 (pcu/hg)

45
STEP C-3 Base Saturation Flow (S)
  • If right-turning movement gt 250 pcu/h, protected
    signal phasing should be considered
  • For No Separate RT-lane
  • If QRTO lt 250 pcu/h
  • Determine SPROV for QRTO 250 pcu/h
  • Determine Actual S as
  • S SPROV (QRTO - 250) x 8pcu/h

46
STEP C-3 Base Saturation Flow (S)
  • For No Separate RT-lane
  • If QRTO gt 250 pcu/h
  • Determine SPROV for QRTO and QRT 250 pcu/h
  • Determine Actual S as
  • S SPROV (QRTO QRT - 500) x 2pcu/h
  • If QRTO lt 250 pcu/h and QRT gt 250 pcu/h
  • Determine S as for QRT 250 pcu/h

47
STEP C-3 Base Saturation Flow (S)
  • For Separate RT-lane
  • If QRTO gt 250 pcu/h
  • QRT lt 250 pcu/h Determine S from Figure C33
    through extrapolation
  • QRT gt 250 pcu/h Determine SPROV as for QRTO and
    QRT 250 pcu/h
  • If QRTO lt 250 pcu/h and QRT gt 250 pcu/h
  • Determine S from Figure C33 through
    extrapolation

48
STEP C-4 City Size Adjustment Factor FCS Table
C-43 p.2-53
City Size Inhab. (M) FCS
Very Small ? 0,1 0,82
Small gt 0,1 - ? 0,5 0,88
Medium gt 0,5 - ? 1,0 0,94
Large gt 1,0 - ? 3,0 1,00
Very Large gt 3,0 1,05
49
STEP C-4 Side Friction Adjustment Factor FSF
Table C-44 p.2-53
50
STEP C-4 Side Friction Adjustment Factor FSF
Table C-44 p.2-53
51
STEP C-4 Side Friction Adjustment Factor FSF
Table C-44 p.2-53
52
STEP C-4Gradient Adjustments Factors FG Figure
C-41 p.2-54
If G ? 0 ? 1 (0,01 x G)
If G lt 0 ? 1 (0,005 x G)
53
STEP C-4 Effect of Parking Adjustments Factors
FP Figure C-42 p.2-54
  • LP ? distance between stop-line
  • and first parked vehicle (m)
  • WA ? Width of the approach (m)
  • g ? Green time in the approach (default value 26
    sec)
  • It should not be applied in cases were the
    effective width is determined by the exit width.

54
STEP C-4 Right Turn Adjustments Factors FRT
FRT 1.0 pRT x 0.26
55
STEP C-4 Left Turn Adjustments Factors FLT
FLT 1.0 - pLT x 0.16
56
Calculated the adjusted value of saturation flow
S
  • SO ? Base saturation flow
  • FCS ? City size
  • FSF ? Side friction
  • FG ? Gradient
  • FP ? Parking
  • FRT ? Right turn
  • FLT ? Left turn

57
STEP C-5 Flow/Saturation Flow Ratio
  • Calculate the Flow Ratio (FR) for each approach
  • Calculate the Intersection Flow Ratio (IFR)
  • Calculate the Phase Ratio (PR) for each phase

Sum of the critical (highest) flow ratios for all
consecutive signal phases in a cycle
58
STEP C-6 Cycle Time and Green Time
  • Unadjusted cycle time (Cua)
  • Green time (g)
  • Adjusted cycle time (c)

LTI S off all intergreen periods
2 phase ? 40-80 sec 3 phase ? 50-100 sec 4 phase
? 80-130 sec
green times lt 10 sec should be avoided !!!
59
STEP D-1 Capacity
  • Calculate the capacity of each approach
  • Calculate the Degree of Saturation

Acceptable value normally 0,75 !!!
If the signal timing has been correctly done, DS
will be nearly the same in all critical
approaches !!!
60
STEP D-2 Need For Revisions
  • Increase of approach width (especially for the
    approaches with the highest critical FR value)
  • Changed signal phasing (i.e. separate phase for
    right-turning traffic)
  • Prohibition of right turning movements will
    normally increase capacity (i.e. reduction of the
    phase required).

61
STEP E-1 Preparations
  • Fill in the information required in the head of
    Form SIG-V

62
STEP E-2 Queue Length
  • For DS gt 0,5
  • NQ1 ? number of pcu that remain from the previous
    green phase
  • DS ? degree of saturation Q/C
  • GR ? green ratio
  • C ? capacity (pcu/h) saturation flow x green
    ratio
  • For DS ? 0,5

63
STEP E-2 Queue Length
  • NQ2 ? number of queuing pcu that arrive during
    the red phase
  • GR ? green ratio g/c
  • g ? green time (sec)
  • c ? cycle time (sec)
  • DS ? degree of saturation Q/C
  • Q ? traffic flow (pcu/h)

64
STEP E-2 Queue Length
  • QL ? Queue length (m)
  • NQMAX ? adjust NQ with desired probability for
    overloading for planning and design ? 5, for
    operation 5-10 figure E-22 p.2-66
  • 20 ? average area occupied per pcu (20 sqm)
  • WENTRY ? entry width (m)

65
STEP E-3 Stopped Vehicle
  • NS ? stop rate
  • NQ ? total number of queuing vehicle
  • Q ? traffic flow (pcu/h)
  • c ? cycle time (sec)

66
STEP E-3 Stopped Vehicle
  • NSV ? number of stopped vehicles
  • Q ? traffic flow (pcu/h)
  • NS ? stop rate

67
STEP E-4 Delay
  • A ?
  • GR ? green ratio
  • DS ? degree of saturation Q/C

68
STEP E-4 Delay
  • DT ? mean traffic delay (sec/pcu)
  • c ? cycle time (sec)
  • NQ1 ? number of pcu that remain from the previous
    green phase
  • C ? capacity (pcu/h)

69
STEP E-4 Delay
  • DGj ? mean geometric delay for approach j
    (sec/pcu)
  • pSV ? proportion of stopped vehicles in the
    approach MIN (NS, 1)
  • pT ?proportion of turning vehicles in the
    approach
  • Geometric Delay for LTOR 6 sec p.2-69

70
STEP E-4 Delay
  • DI ? average delay for the whole intersection
  • Average delay can be used as an indicator of the
    Level of Service (LOS) of each individual
    approach as well as of the intersection as a
    whole.

71
Indeks Tingkat Pelayanan (ITP) Lalulintas Di
Persimpangan Dengan Lampu Lalulintas
Indeks Tingkat Pelayanan (ITP) Tundaan per kendaraan (detik)
A 5.0
B 5.1 15.0
C 15.1 25.0
D 25.1 40.0
E 40.1 60.0
F gt 60.0
Sumber Perencanaan Pemodelan Transportasi,
Tamin, 2000
72
Cara-cara untuk meningkatkan kapasitas Simpang
Bersinyal
  • Pelebaran lengan pendekat
  • Kapasitas tergantung pada arus jenuh yang
    melewati garis henti (lebar lengan pendekat).
  • Melebarkan lengan pendekat ? meningkatkan
    kapasitas persimpangan.
  • Panjang dari pelebaran lengan pendekat juga
    sangat penting untuk diperhatikan.

73
Cara-cara untuk meningkatkan kapasitas Simpang
Bersinyal
  • Menaikkan waktu siklus
  • semakin lama waktu siklus ? semakin besar
    kapasitas persimpangan ? semakin tinggi antrian
    dan tundaan yang terjadi
  • Menurut MKJI 1997 p.2-60 kisaran waktu siklus
    adalah 40 s/d 130 detik
  • Pada kondisi tertentu terpaksa digunakan waktu
    siklus gt 130 detik.

74
Cara-cara untuk meningkatkan kapasitas Simpang
Bersinyal
  • Perubahan pola fase
  • Perlu dilakukan simulasi untuk mendapatkan pola
    fase yang paling efisien.
  • Semakin sedikit fase ? semakin tinggi kapasitas
    persimpangan ? semakin besar kemungkinan konflik
    yang dapat terjadi.
  • Umumnya jumlah fase yang digunakan berkisar
    antara 2 s/d 4.
  • Siklus dengan 2 fase umumnya dilengkapi dengan
    early cut-off atau late-start. ? persimpangan
    Raya Darmo Polisi Istimewa

75
Cara-cara untuk meningkatkan kapasitas Simpang
Bersinyal
  • Meminimalkan waktu antar-hijau
  • Waktu antar-hijau diperlukan untuk menjamin
    keamanan kendaraan yang melewati simpang pada
    saat detik akhir hijau, agar tidak tertabrak
    kendaraan yang mendapatkan fase hijau berikutnya.
  • Meminimalkan waktu hijau ? mendekatkan garis
    henti dengan pusat persimpangan.

76
Cara-cara untuk meningkatkan kapasitas Simpang
Bersinyal
  • Larangan belok kanan
  • Meningkatkan kapasitas akibat pengurangan fase.
  • Namun harus dilakukan manajemen lalulintas untuk
    melayani kendaraan yang hendak belok kanan dengan
    menyediakan U-turn atau Re-routing.

77
Prinsip-prinsip desain simpang secara umum di
Indonesia
  • Jari-jari tikungan berkisar antara 6 s/d 9 meter
  • Hindari jari-jari terlalu kecil ? kendala manuver
    bagi bus truk
  • Fasilitas penyeberang jalan (zebra cross) ? 2,5
    s/d 5 meter sejarak 2 meter didepan garis henti
  • Panjang pelebaran harus lebih besar dari
    probabilitas panjang antrian terbesar

78
Prinsip-prinsip desain simpang secara umum di
Indonesia
  • Jalur khusus bus berakhir pada awal panjang
    antrian terbesar
  • Jika arus lalulintas belok kanan cukup besar,
    perlu dibuatkan jalur khusus belok kanan
    dilengkapi dengan rambu dan marka yang sesuai
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