Capacity & Level of Service: Highways & Signalized Intersections (Indo-HCM)

Capacity & LOS for Highways &
Signalized Intersections with Mixed Traffic
(Indo-HCM)
Sethulakshmi G (207CV009)
Vijai Krishnan V (207CV013)
CV852: Traffic Engineering & Management
Department of Civil Engineering
NITK, Surathkal

Overview
 Introduction
 Indo-HCM
 Outline of Indo-HCM
 Outline of US-HCM
 Capacity & LOS of Highways
• Capacity & LOS using Indo-HCM
• Comparison with US HCM
 Capacity & LOS of Signalized Intersections
• Capacity & LOS using Indo-HCM
• Comparison with US HCM
 Conclusions
2
CV852 TP09 | | Capacity & LOS: Indo-HCM
16-Dec-20

Introduction
 Widely used - US-HCM (1950)
 Base conditions and capacity depend on local conditions
 Why Indo-HCM?
• Heterogeneous traffic – diverse vehicles & road users
• Different classification of roadways
• Absence of lane markings & lane discipline - complex maneuver
• Rapid vehicular growth - delay, congestion, long queues
 Manual should co-exist with prevailing conditions of the country
3
16-Dec-20

Indo-HCM
 12th Five Year Plan Project
 Developed by CSIR-CRRI & 7
academic institutions
 Released on 12th Feb 2018 by
Hon’ble Minister Shri. Nitin Gadkari
4
(Source: www.insightsonindia.com)
16-Dec-20

Outline of US-HCM
 Volume 1: Concepts
 Volume 2: Uninterrupted Flow
 Volume 3: Interrupted Flow
 Volume 4: Applications Guide
CV852 TP09 | | Capacity & LOS: Indo-HCM 5
• Freeways
• Multi-lane highways
• Two lane highways
• Freeways
• Multi-lane highways
• Two lane highways
• Urban street
segments & facilities
• Intersections
• Off-street pedestrian
& bicycle facilities
• Urban street
segments & facilities
• Intersections
• Off-street pedestrian
& bicycle facilities
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Outline of Indo-HCM
 Formulation of Methodology
• 1st National Level Workshop, SVNIT, 2013
 9 Work Packages
 10 Chapters
 Different classes of roads considered
separately
 Addressed pedestrian facilities and
travel time reliability as a performance
measure
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Contd…
Chapter No. Title
Chapter 1 Basic Concepts and Structure of the Manual
Chapter 2 Two Lane, Intermediate and Single Lane Roads
Chapter 3 Multilane Interurban Highways
Chapter 4 Inter urban and Urban Expressways
Chapter 5 Urban Roads
Chapter 6 Signal Controlled Intersections
Chapter 7 Roundabouts
Chapter 8 Uncontrolled Intersections
Chapter 9 Pedestrian Facility
Chapter 10 Reliability as a Performance Measure for Inter-urban and Urban Arterial
16-Dec-20
Table 1 Table of contents of Indo-HCM 2017

Contd…
 Test sections throughout India
 Field data collection & analysis at mid-block & intersections
 All possible combinations geometry and operating conditions
 Established relationship between variables influencing traffic to
characterize heterogeneous traffic flow
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Capacity & LOS of Highways
(Single lane, Intermediate lane and Two lane highways)
9
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Capacity & LOS using Indo-HCM
16-Dec-20
Two Lane Road Intermediate Lane Road Single Lane Road
Data Collection
Traffic Data Geometric Data
Estimation of Dynamic PCU
Estimating Stream Equivalency Factor
Estimating Base Capacity
Estimating Adjusted Capacity
Number of Followers
Operating Speed
Level of Service (LOS)
LOS based on v/c Ratio
(Single Lane Road)
LOS based on NFPC
(Two & Intermediate Lane Roads)
Figure 1 Indo-HCM methodology for capacity & LOS of two-lane highways (Indo-HCM, 2017)

 Step 1: Input data
Geometric
Data
Type of carriageway (Two-lane, intermediate lane, single lane)
Carriageway width
Type of shoulder & width (soft/hard shoulders)
Terrain type (plane, rolling, mountainous, steep)
Pavement condition (IRI)
Horizontal curvature
Traffic
Data
Traffic volume & composition
Length of analysis period (5min)
Directional split (50:50)
Speed of different types of vehicles
Free-flow speed of cars
Table 2 Input data required for capacity analysis of two-lane highways (Indo-HCM, 2017)
16-Dec-20

 Step 2: Estimation of speed
• Vehicle operating speed (Vos) = 85th percentile of Free Flow Speed
(FFS)
• Free Flow Speed (FFS)
o Minimum random sample of 100 vehicles
o Standard car with headway ≥ 8 sec
 Step 3: Estimation of Passenger Car Units (PCU)
• Dynamic PCU is estimated using Chandra’s method
• VC and Vi are speed of standard car & vehicle type ‘i‘, & AC & Ai are
respective projected rectangular area
16-Dec-20
(Eqn-1)

Table 3 PCU values suggested in Indo-HCM (Indo-HCM, 2017)
Vehicle Type Single lane road Intermediate & Two-lane
Standard Car (SC) 1.00 1.00
Big Car (BC) 1.60 1.60
Motorized Two Wheeler (TW) 0.25 0.30
Auto rickshaw 1.20 1.20
Bus (B) 4.50 4.50
LCV 2.70 3.00
Two/Three Axle Truck (TAT) 4.80 5.00
Multi Axle Truck (MAT) 5.00 6.00
Tractor/ Tractor Trailer (TT) 7.00 7.00
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 Stream Equivalency Factor (Se or SEF)
• To account dynamic nature of PCU
• PCU values vary with traffic volume or composition
• Traffic stream is composed of vehicles larger than standard cars  Se
will be higher
Se
IL/TL = 1 + 0.150*PBC – 0.702*PTW + 0.204*PAUTO + 1.770*PLCV + 5.075*PBUS +
3.550*PTAT + 4.598*PTT + 5.414*PMAT – 1.239/N
(Eqn-2)
16-Dec-20
(Eqn-3)

 Step 4: Capacity determination
• Indo-HCM defines two types of capacity
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 Base Capacity
Maximum number of vehicles that can pass a given point on a lane on a
roadway during one hour, under the most nearly ideal roadway and traffic
conditions, which can be possibly attained.
 Adjusted Capacity
• Maximum number of vehicles that can pass a given point on a lane on a
roadway during one hour, under the prevailing roadway and traffic conditions.
• Obtained by adjusting base capacity for roadway & traffic conditions present
at site.

• Linear relationship between
operating speed of standard car
and capacity
16-Dec-20 CV852 TP09 | | Capacity & LOS: Indo-HCM 16
Figure 2 Relationship between operating
speed and capacity of two-lane road
(Indo-HCM, 2017)
Two – lane road
394 +34*VOS
Intermediate – lane road
830 +16.4*VOS
Single – lane road
187 +12.4*VOS
Base Capacity
(Eqn-4)
(Eqn-5)
(Eqn-6)

 Step 5: Adjustment of base capacity
Adjustment factor Description
Carriageway width (fw) • 1 for base condition (Two lane-7m, intermediate lane 5.5, single-lane 3.75m)
• Increases with increase in carriage way width
Paved shoulder (fps) • 1 for paved shoulder width = 0 m
• Increases with increase in shoulder width
Directional spilt (fds) • 1 for 50:50
• Decreases towards 100:0 (0.836)
Road geometry •1 for straight and level terrain
•Vos(km/h) = 70.6 – 1.84*Gradient – 0.026*Curvature (Eqn-7)
•Capacity = 23.6*Operating speed + 167 (Eqn-8)
Riding quality • Used to account surface condition
• For two lane road, VOS = 104 – 6.8*IRI (Eqn-9)
• For intermediate lane road, VOS = 91 – 6.7*IRI (Eqn-10)
• Capacity: Two-lane road = 5082 – 275*IRI (paved shoulder) (Eqn-11)
= 3677 – 203*IRI (without paved shoulder) (Eqn-12)
Intermediate lane road = 2956 – 199*IRI (Eqn-13)
Single lane road = 945 – 25*IRI (Eqn-14)
Table 4 Adjustment factors for base capacity – Indo HCM
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 Step 6: LOS Determination
• Qualitative measure of
performance of highway
• Helps in design and upgradation
of roadway facility
• Planning of upgrading a facility
should be started when lower
limit of LOS B is reached
• LOS:
o Two lane
o Intermediate lane
o Single lane  v/c ratio
where,
Q = two-way traffic volume (PCU/h)
NF = Number of followers (PCU/h)
NFPC = No. of Followers as
Proportion of Capacity
NFPC
NFPC = NF/Base capacity
NF = 1.1742*Q0.9306
(Eqn-15)
(Eqn-16)

LOS NFPC
A < 0.15
B 0.15-0.25
C 0.26-0.40
D 0.41-0.55
E 0.56-0.70
F > 0.71
LOS v/c Ratio
A ≤ 0.15
B 0.16 - 0.30
C 0.31 - 0.50
D 0.51 - 0.80
E 0.81 - 1.00
F > 1.00
Table 5 LOS criteria for intermediate and
two-lane roads – Indo HCM
Table 6 LOS criteria for single lane roads –
Indo HCM
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Comparison with US-HCM
16-Dec-20
Indo-HCM US-HCM
Geometric
Data
Type of carriageway (Two-lane, intermediate lane, single lane) Highway class (Class-I, Class-II, Class-III)
Carriageway width Lane width (12ft)
Type of shoulder & width (soft/hard shoulders) Shoulder width (6ft)
Terrain type (plane, rolling, mountainous, steep) Terrain (level, rolling)
Pavement condition (IRI) Pavement condition
Horizontal curvature Access point density
Percent no-passing zone
Base design speed (Speed limit+10 mph)
Length of passing lane
Traffic
Data
Traffic volume & composition Hourly volume
Length of analysis period (5min) Length of analysis period (15min)
Directional split (50:50) Directional split (60:40)
Speed of different types of vehicles Peak Hour Factor (0.88)
Free-flow speed of cars Heavy vehicle percentage (PT=6%)
Table 7 Comparison of input data

 LOS:
• Class I highway  ATS & PTSF (worst)
• Class II highway  PTSF
• Class III highway  PFFS
16-Dec-20
LOS
Class I Highways Class II Highways Class III Highways
ATS (mi/h) PTSF (%) PTSF (%) PFFS (%)
A >55 ≤ 35 ≤ 40 >91.7
B 50 – 55 35 – 50 40 – 55 83.3 – 91.7
C 45 – 50 50 – 65 55 – 70 75 – 83.3
D 40 – 45 65 – 80 70 – 85 66.7 – 75.0
E ≤ 40 >80 >85 ≤ 66.7
Table 8 LOS criteria for two-lane highways (HCM, 2010)

16-Dec-20
• Determination of Average Travel Speed (ATS)
o Free flow speed
o Demand flow rate
o Adjustment for percentage no passing zone
• Determination of Percent Time Spent Following (PTSF)
o Base Percent Time Spent Following (BPTSF)
o Demand flow rate
o Adjustment for percentage no passing zone
• Determination of Percentage Free Flow Speed (PFFS) =ATS/FFS

• Determination of FFS
o Direct measurement under low demand condition
o Adjusting the mean speed obtained from field measurement at higher flow
rates
o Adjusting the Basic Free-Flow Speed (BFFS) for lane and shoulder width and
access-point density (BFFS = Posted speed limit+10mph)
• Determination of Demand Flow Rate
o Ratio of the corresponding demand volume to Peak Hour Factor (PHF) and
adjustment factors for grade and heavy vehicles.
16-Dec-20

 Capacity:
• Base capacity of two lane highway = 1700 pcu/hr/direction
• Capacity under prevailing condition  Multiply base value with
adjustment factors for grade and heavy vehicles
o Class I highways
 Compute ATS and PTSF-based capacities (least one is chosen)
o Class II highways
 Compute PTSF-based capacity
o Class III highways
 Compute ATS-based capacity
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Sample Problem 1
Determine the capacity and Level of Service (LOS) for a two-
lane two-way road in plain terrain. The two way traffic volume is
enumerated as 608 veh/h and directional split is 50:50. Width of
carriageway is 7.0 m and operating speed on the section is
75kmph. The observed traffic flows and estimated PCU values
are given below.
16-Dec-20

Vehicle Type SC BC Bus TW Auto LCV TAT MAT TT
Estimated PCU 1.00 1.29 2.80 0.31 1.18 2.52 3.35 5.22 6.3
Time Interval (Mins.) SC BC TW Auto LCV Bus TAT MAT TT Total
0 - 15 23 6 87 14 5 2 8 3 5 153
15 -30 14 6 94 2 11 12 3 3 6 151
30 -45 45 14 59 8 8 3 6 6 3 152
45 -60 36 12 46 14 5 2 26 5 6 152
Total hourly volume 118 38 286 38 29 19 43 17 20 608
Composition (%) 19.4 6.3 47.0 6.3 4.8 3.0 7.1 2.8 3.3 100.0
Table A1 Observed traffic volume
Table A2 Estimated PCU values
16-Dec-20

 Solution:
• Input Data:
o Two way traffic volume = 608 veh/h
o Directional split = 50/50
o Carriageway width = 7.0 m
• Estimation of Total Traffic Volume in PCU/h:
o Total traffic volume is obtained by multiplying the number of vehicles under
each category with the respective PCUs
Vehicle Type SC BC Bus TAT LCV Auto TW TT MAT Total PCU/h
Total hourly volume (veh/h) 118 38 19 43 29 38 46 6 5
Q = 785
PCU value 1.0 1.29 2.80 0.31 1.18 2.52 3.35 5.22 6.3
PCU/h 118 49 53 144 73 45 88 126 59
Table A3 Total Hourly Traffic Flow in PCUs
16-Dec-20
o Operating speed = 75kmph
o Terrain = Plain

• Calculation of Base Capacity
o Base capacity for two lane road = 394 + 34*VOS = 394 + 34*75 = 2944 PCU/h
• Estimation of Number of Followers (NF)
o NF = 1.1742*Q0.9306 = 1.1742*(785)0.9306 = 580 PCU/h
• Estimation of Number of Followers as Percentage of Capacity (NFPC)
o NFPC = 580/2944 = 0.197
LOS corresponding to NFPC of 0.197 is B
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Capacity & LOS of Signalized Intersections
29
16-Dec-20

Signalized Intersections
(Source: Hidustan Times)
(Source: Palm Beach Post)
(Source: Times of India)
 Critical locations: Non-lane
based movements & complex
maneuvers
 Working principle :
• Allocation of right of way to non-
conflicting movements in a cyclic
manner
• To minimize delay and conflicts

Capacity & LOS using Indo-HCM
 Base intersection
• All approaches have uniform width up to stop line
• No bus stop within 75m from the nearest stop line
• Negligible pedestrian flow
• Longitudinal gradient is zero for all approaches
• While waiting for the phase, right-turning vehicles shall not hinder the
movement of through vehicles
 Apply adjustments for non-base intersections
16-Dec-20

Input
Geometric Data
Traffic Data
Control Data
Field Saturation Flow
Measurement
Estimation Base Saturation Flow &
Adjusted Saturation Flow
Saturation Flow in PCU
Saturation Flow in PCU
Capacity Analysis Capacity Analysis
Field Stopped Delay
Measurement
Conversion of Stopped
Delay to Control Delay
Estimation of Control
Delay using Delay Model
Level of Service
Figure 3 Indo-HCM methodology for capacity and LOS estimation of signalized intersections
16-Dec-20

 Step1: Input Data
Parameter type Parameter
Geometric data Approach width
Presence of exclusive lanes for right or free left turn
Presence of bus bays or curbside bus stop
Traffic data Classified peak hour volume
PCU factors
Unit base-saturation flow rate, USF0 (PCU/h/m)
No. of buses stopping at intersection (bus/h)
Presence of approach flare & anticipated early movement & resulting initial surge
Control
characteristics
Cycle time, CT (sec)
Green time, G (sec)
Change and clearance interval, Y (sec)
Phase plan
Analysis period, T (hours) = 15min
Table 9 Input data for capacity analysis of signalized intersections (Indo-HCM, 2017)
16-Dec-20

 Step 2: Estimation of saturation flow
• Unit base saturation flow  Saturation flow per unit width of approach
USF0 = unit base saturation flow rate (PCU/h/m)
w = effective width of approach (m)
• Prevailing saturation flow rate (SF) in PCU/hr
SF = w x USF0 x fbb x fbr x fis
630 ; w < 7.0m
USF0 = 1140 – 60w ; 7.0 ≤ w ≤ 10.5m
500 ; w ≥ 10.5
(Eqn-17)
16-Dec-20
(Eqn-18)

fbb = adjustment factor for bus blockage =
tb = average blockage time during green (sec) = 18 sec
nB = no. of buses stopping in an hour ≤ 200
fbr = adjustment factor for blockage of through vehicles by standing right turning vehicles
waiting for the phase (not applicable if exclusive right turn lanes are present)
= (w – wr)/w
wr = width of approach occupied by standing vehicles waiting for right turn phase = 2.5m
(default value)
fis = adjustment factor for initial surge = 1 (if no surge flow is observed)
o Initial surge
 Due to anticipation effect/approach flare effect/both
 Adjustment has to be given only for effect that is present
(Eqn-19)
16-Dec-20
(Eqn-20)

 Step 3: Estimation capacity and v/c ratio
• Capacity of movement group ‘i' in PCU/h
Ci = SFi (gi/CT)
SFi = prevailing saturation flow rate for movement group ‘i' (PCU/h)
gi = effective green time for movement group ‘i' (sec)
CT = overall cycle time (sec)- Webster’s Method
• Calculate degree of saturation
Xi = vi/Ci
• Critical v/c ratio of intersection
= summation of flow ratios for all critical movement group ‘i‘
L = total lost time per cycle
(Eqn-21)
(Eqn-23)
(Eqn-22)
16-Dec-20

 Step 4: Estimation of delay
• Control delay (d)
o Average delay due to traffic signal
o Includes stopped delay and lost time
o Control delay in India is similar to control delay model in US-HCM
d1 = uniform delay
d2 = incremental delay
d3 = delay which accounts for presence of initial queue before start of analysis period
16-Dec-20
d = 0.9*d1 + d2 + d3 (Eqn-24)

• Average control delay for approach-A
di = average control delay for movement group ‘i' (sec/PCU)
Vi = volume of movement group ‘i'
• Intersection delay: Weighted average of delay for each approach
VA = volume of approach ‘A’
16-Dec-20
(Eqn-25)
(Eqn-26)

 Step 5: Estimation of LOS
• LOS for an approach or entire intersection can be estimated using
control delay and v/c ratio
LOS Control Delay (sec/PCU)
A 20
B 20 - 40
C 40 - 65
D 65 - 95
E 95 - 130
F >130
LOS v/c ratio
A <0.45
B 0.46 – 0.75
C 0.76 – 0.95
D 0.96 – 1.05
E 1.06 – 1.10
F >1.10
Table 10 LOS based on control delay –
Indo HCM
Table 11 LOS based on v/c ratio
– Indo HCM
16-Dec-20

Comparison with US-HCM
 Almost similar methodology
 Calculate flow rate for each
lane group
 Determine base saturation
flow rates
 Find adjusted saturation flow
rate
• Adjustments:
o Lane width
o Heavy vehicles
o Approach grade,
o Parking lane or parking activity
o Type of area
o Lane utilization
o Presence of left and right turn
vehicles
o Pedestrian - bicycle groups
o Bus blockage

 Estimate capacity and v/c ratio
 Delay = uniform delay(d1)+
Incremental delay(d2) + Initial
queue delay(d3)
• Delay and queue size  Proportion of
vehicles arriving
• Larger proportion of vehicles during
green time  Less delay and queue size
 Estimate LOS
• Intersection or approach  Control
delay
• Lane group  control delay & v/c ratio
 Performance measure - Queue
Storage Ratio
• Proportion of available queue
storage distance occupied at the
point in the cycle when the back
of queue position is reached
• Value >1  Storage space will
overflow and block other vehicles

Control Delay
LOS by v/c ratio
≤ 1.0 > 1.0
≤ 10 A F
10 – 20 B F
20 – 35 C F
35 – 55 D F
55 – 60 E F
>60 F F
Table 12 LOS criteria for signalized intersection – US HCM 2010
16-Dec-20

Sample Problem 2
 Estimate the capacity and LOS of all approaches and the entire
signalized intersection given below. All approaches have uniform
width.
Figure B1 Intersection configuration
16-Dec-20

Details SB WB NB EB
Approach width, w 7m 7m 7m 7m
Demand volume 935 PCU/h 856 PCU/h 756 PCU/h 587 PCU/h
PHF 0.9 0.9 0.9 0.9
Exclusive right lane No No No No
Bus bays No No No No
No. of buses stopping at intersection, nB 0 45 buses/h 112 buses/h 0
Initial surge Yes No No No
Anticipation effect Yes No No No
Approach flare effect No No No No
Surge ratio 1.15 - - -
Approach delay 45 s/PCU 50 s/PCU 56 s/PCU 38 s/PCU
Table B1 Geometric, traffic and control characteristics
16-Dec-20

Phase
Phase
movement
Green Time
(sec)
Amber Time
(sec)
1 25 3
2 25 3
3 25 3
4 25 3
Table B2 Phase plan
Given, fis = 1.067 for anticipation effect & green time between 15 – 30
sec.

 Solution:
Phase Eqn. No. Phase 1 Phase 2 Phase 3 Phase 4
Approach - - SB - - WB - - NB - - EB -
Approach width, w (m) - - 7 - - 7 - - 7 - - 7 -
USF0 (PCU/h) 17 - 720 - - 720 - - 720 - - 720 -
fbb 19 - 1 - - 0.903 - - 0.760 - - 1 -
fbr (given-uniform width) 20 - 1 - - 1 - - 1 - - 1 -
fis - - 1.067 - - 1 - - 1 - - 1 -
SF (PCU/h) 18 - 5378 - - 4551 - - 3830 - - 5040 -
g = Green time – Lost time - - 22 - - 22 - - 22 - - 22 -
Capacity, C (PCU/h) 21 - 1056 - - 894 - - 752 - - 990 -
Approach delay (s/PCU) - - 45 - - 50 - - 56 - - 38 -
Approach LOS (Table 10) - - C - - C - - C - - B -
VA = Demand volume*PHF - - 842 - - 770 - - 680 - - 528 -
Intersection delay (s/PCU) 26 48
Intersection LOS (Table 10) C
16-Dec-20
Table B3 Capacity estimation

Conclusions
 Necessary to asses performance of road ways, design and up
gradation
 Geometric, traffic and control characteristics depend on local
condition
 Cannot directly apply other country’s manual
 Indo-HCM provide methodology for LOS and Capacity
estimation in mixed traffic
 Addressed different classes of roads, intersections and
pedestrian facilities
16-Dec-20

 In computing capacity & LOS adjustment factors are used for
deviation from base condition
 Estimation of capacity and LOS of highway In INDO-HCM 
Operating speed
 Capacity and LOS of two lane highway in US-HCM  ATS, PTSF &
PFFS
 Both HCM use control delay for evaluating LOS on signalized
intersection
16-Dec-20

References
1. Arkatkar, S., Mitra S., and Mathew, T. V., 12 – India, Global Practices on Road
Traffic Signal Control, Elsevier, 2019, pp. 217 – 242.
2. Arun, A., Velmurugan, S. and Erampalli M. (2013) Methodological Framework
towards Roadway Capacity Estimation for Indian Multi-lane Highways,
Proceedings of 2nd Conference of Transportation Research Group of India,
Procedia-Social and Behavioral Sciences, 104, 477 – 486.
3. HCM 2010, Highway Capacity Manual, Transportation Research Board,
Washington D.C., 2010.
4. Indo-HCM 2017, Indian Highway Capacity Manual, CSIR-CRRI, New Delhi,
2017.
5. Savitha, B. G., Satyamurthy, R., Jagadheesh, H. S., Satish, H. S. and
Sundararajan, T. (2020) Evaluation of Level of Service at few Signalized
Intersections using Indian Highway Capacity Manual (Indo-HCM, 2018),
Proceedings of AIP Conference 2204, 1 – 9.
16-Dec-20

Capacity & Level of Service: Highways & Signalized Intersections (Indo-HCM)

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