The document presents a study on quantifying the level of service of a typical two-lane highway. Traffic data was collected through classified volume counts, spot speed surveys, and videographic techniques on NH-44 near Agartala, India. Analysis of the data showed hourly traffic variations with peak periods. Speed distributions were established and fitted to normal curves. Vehicle arrival patterns were found to follow a Poisson distribution. Speed-flow relationships were developed using regression analysis. The study aims to help establish parameters for evaluating level of service on two-lane highways with mixed traffic conditions.

1. AN APPROACH TO STUDY THE
LEVEL OF SERVICE ON A TYPICAL
TWO LANE HIGHWAY
SUBMITED BY
JAYASHREE KAR (ENROLLMENT NO.-0710110)
PRALOYBRATA RAKSHIT ( ENROLLMENT NO.-0710116)
PRANABESH SEN (ENROLLMENT NO.-0710)
A PROJECT REPORT ON

2. An approach
Rural highway is designed for the design service volume
expressed in terms of PCU/Hr. which corresponds to LOS
B.
 PCU factor as per the guidelines is invariably applied
irrespective of the roadway configuration i.e. two lane, four
lane, divided, undivided etc.
It was observed that on a two lane highway it is difficult to
have the desired LOS for any particular volume of traffic
due to reduction of speed and subsequent delay.
An attempt was made to find an approach to quantify LOS
of a two lane road based on certain attributes.

3. On an average day about 90,000 vehicles enter and
exit in Agartala city through the major arterial road NH-44.
NH-44 is popularly known as the Assam-Agartala Road
with a total road length of 333 km between Sabroom to
Shillong.
The configuration is two lane with 1m poorly maintained
earthen shoulder on either side.
Prevailing traffic condition is heterogeneous consisting
of both motorized and non motorized traffic.
An overview

4.  Speed-flow and speed-density relationship
should be developed.
 Free-flow speed distribution pattern needs to
be established.
 Estimation of headway distribution parameter
as a feed data in the simulation model.
 Establishing vehicle arrival pattern in a stated
interval of time i.e. 60 s.
To meet the objective

5.  As per HCM 2000, free flow speed to be
measured when the traffic flow is low i.e. 200
pc/ h
 To develop fundamental traffic flow
relationship, stretch with higher density is
normally preferred.
 Straight stretch, horizontal curve and vertical
curve should be studied separately.
Requirements…..

6.  It was necessary to conduct classified traffic
volume count to determine hourly variation of
traffic and vehicular composition.
 Ch.471+000 near Khyerpur on NH-44 was
selected for the entire study e.g. speed-flow,
speed-density, free-speed, gap-studies and
arrival pattern of vehicle.
How and where???

7. Analysis and Discussion

8. PARAMETERS DESCRIBING TRAFFIC FLOW
Volume (or flow rate i.e. ‘q’): The number of
vehicles passing a fixed point in unit time.
Typical units are veh/day, veh/hr or veh/sec.
Speed (or velocity i.e. ‘v’): The distance travelled
by a vehicle in unit time. Typical units are km/h
(also kmph) or m/s.
Density (or concentration i.e. ‘k’): The number of
vehicles per unit length of lane or road, at a given
time instant. Typical unit is veh/km.

9. Parameters describing traffic flow(contd.)
Headway (or time spacing i.e. ‘h’): The time gap
between successive vehicles in a traffic stream
(actually between the same points on the vehicles, e.g.
front of vehicle). Typical unit is seconds. Can be in
space unit also.
Spacing (or the space headway i.e.‘s’): The
distance between the same physical points (e.g.
front of vehicle) on two successive vehicles in a
traffic lane. Typical unit is m.

10.  Parameters describing traffic flow(contd.)
Capacity: The capacity of a facility is the
maximum hourly rate at which persons or
vehicles reasonably can be expected to traverse
a point or a uniform section on a lane or
roadway during a given time period under
prevailing roadway, traffic and control
conditions.

11. Flow
(Q)
Speed
(V)
Capacity =QMax
Free Speed =VF
VF/2

12. Speed
(V)
Density (k)
Free Speed =VF
Jam Density=kmax

13. Level of service in highway capacity manual
(HCM, 2000) is defined as
“A qualitative measure describing operational
condition within a traffic stream, based on
service measures such as speed and travel time,
freedom to maneuver traffic interruption,
comfort, and convenience.”

14.  A– Fee flow, low volumes, high speeds
(100 kph), freedom of manoeurability
 B– Stable flow, reasonable freedom to
manoeuvre and speeds (95kph)
 C– Still stable flow, speeds (90 kph) and
manoeuvability controlled by higher
volumes

15.  D– Approaches unstable flow, tolerable
operating speed (75 kph), little freedom to
manoeuvre
 E– Unstable flow, volumes nearing
capacity, low speeds (60 kph)
 F-Forced flow, low speed (50 kph), stop and go
operations

16. Volume-Capacity Ratio
1.0
Capacity
LOS A
LOS B
LOS C
LOS D
LOS E
LOS F
Typical Speed-Flow Curve with LOS for
Multi-lane Highway
LOS = Level of
Service
0
Free Speed
Speed

24.  CLASSIFIED VOLUME COUNT
 SPOT SPEED SURVEY
 VIDEOPHOTOGRAPHIC SURVEY

25.  Typical working day was selected.
 Survey was conducted on NH-44 from 8:00am
to 6pm.
 Weather condition was very pleasant.

29. 0
50
100
150
200
250
300
350
400
450
PCU's Hourly Variation of Traffic (PCU/ Hr)
Series1

30. 0
50
100
150
200
250
300
350
400
450 8:00-8:15
8:15-8:30
8:30-8:45
8:45-9:00
9:00-9:15
9:15-9:30
9:30-9:45
9:45-10:00
10:00-10:15
10:15-10:30
10:30-10:45
10:45-11:00
11:00-11:15
11:15-11:30
11:30-11:45
11:45-12:00
12:00-12:15
12:15-12:30
12:30-12:45
12:45-13:00
13:00-13:15
13:15-13:30
13:30-13:45
13:45-14:00
14:00-14:15
14:15-14:30
14:30-14:45
14:45-15:00
15:00-15:15
15:15-15:30
15:30-15:45
15:45-16:00
16:00-16:15
16:15-16:30
16:30-16:45
16:45-17:00
17:00-17:15
17:15-17:30
17:30-17:45
17:45-18:00
Hourly Variation of Traffic (PCU/ Hr)
Series1

31. 0
50
100
150
200
250
300
350
UP
Directional
Traffic
(PCU's) Hourly Variation of UP Directional Traffic (PCU/ Hr)
Series1

32. 0
50
100
150
200
250
300
350
8:00-8:15
8:15-8:30
8:30-8:45
8:45-9:00
9:00-9:15
9:15-9:30
9:30-9:45
9:45-10:00
10:00-10:15
10:15-10:30
10:30-10:45
10:45-11:00
11:00-11:15
11:15-11:30
11:30-11:45
11:45-12:00
12:00-12:15
12:15-12:30
12:30-12:45
12:45-13:00
13:00-13:15
13:15-13:30
13:30-13:45
13:45-14:00
14:00-14:15
14:15-14:30
14:30-14:45
14:45-15:00
15:00-15:15
15:15-15:30
15:30-15:45
15:45-16:00
16:00-16:15
16:15-16:30
16:30-16:45
16:45-17:00
17:00-17:15
17:15-17:30
17:30-17:45
17:45-18:00
Hourly Variation of UP Directional Traffic (PCU/ Hr)
Series1

33.  For free speed study a survey was conducted
on NH-44.
 Time duration from 12:00 to 2:00pm was
selected for survey.
 Spot speed data were collected by using video
photographic technique.

34. Photo view. Spot Speed Survey is carried out
using video camera on NH-44 near Khayerpur

35. Video Camera
Fig. Layout of spot speed survey location using video photographic survey technique
10 m
AGARTALA JIRANIA

37.  Statistical analysis of the observed data was
made to understand the speed characteristics
 Speed data grouped into class interval and
Frequency distribution was done.
 To determine the percentile speed, cumulative
percentage frequency was plotted so as to
develop the cumulative frequency distribution
curve.

38.  The mean speed and standard deviation values were
calculated and were found to be 36 kmph and 13 kmph
respectively.

 Important parameters namely 15th percentile speed (V15), 50th
percentile speed (V50), 85th percentile speed (V85), 95th
percentile speed (V95) and Spread Ratio (SR) were calculated
from this distribution and found to be 20, 35, 48.33, 55 kmph
and 0.888 respectively.
 V15 is used to determine the lower speed limit whereas V85 is
used for upper speed limits and V95 is used as a design speed
for geometric design of highways

39.  The parameter, spread ratio (SR) is used to explain
the normality of the observed data. The SR is
defined as
V85 – V50
SR =
V50 – V15
 SR ranges between 0.69 and 1.35 (Dey, et. al., 2006).
 Therefore, as the estimated SR value is 0.888, the
observed speed frequency data was fitted to normal
distribution using mean and SD of vehicle speeds.

40. Probability Density Function
Histogram Normal
Speed (Kmph)
72
64
56
48
40
32
24
16
8
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0

41. Cumulative Distribution Function
Sample Normal
Speed (Kmph)
72
64
56
48
40
32
24
16
8
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

42. Probability Density Function
Sample Poisson
K=Arrivals per 60 sec. interval
22
20
18
16
14
12
10
8
6
0.24
0.22
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02

43. Cumulative Distribution Function
Sample Poisson
K=Arrivals per 60 sec. interval
22
20
18
16
14
12
10
8
6
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

44. Probability Density Function (Agartala Bound Traffic)
Histogram Exponential
t (sec.)
36
32
28
24
20
16
12
8
4
f(t)
0.4
0.36
0.32
0.28
0.24
0.2
0.16
0.12
0.08
0.04
0

45. Probability Density Function (Jirania Bound Traffic)
Histogram Exponential
t (sec.)
36
32
28
24
20
16
12
8
4
0.36
0.32
0.28
0.24
0.2
0.16
0.12
0.08
0.04
0

46.  The distribution pattern of speed frequency and free speed profiles of
different vehicle class were established for NH-44.
The mean speed and 85th percentile speed of the total observation of
speed data was found to be 36 kmph and 48.33 kmph. The distribution
was fitted to normal distribution as the spread ratio was found to be 0.888
(between 0.69 and 1.35). This attributes to the reduction of capacity and
level of service under the existing mixed traffic condition.
It was observed that only for Two Wheeler and Three Wheeler the
estimated free speed distribution can be fitted to normal distribution
based on the estimated SR.

47. To develop speed-flow and speed density
relationship a Survey was conducted
during peak hour from 8:30am to 10:30am.
The survey was done using video
photographic technique.

48. Fig. Layout of video photographic survey
location using video photographic
survey technique

50.  The traffic data was extracted from the video
recordings.
 The data was entered in the computers for
analysis.

51.  Speed-Flow relationships are the basis for the
determination of the capacity of a road.
 The theoretical speed-flow curve is a parabola and
maximum flow (capacity) occurs at half the free
speed.
 Regression analysis was carried out to study the
relationship between speed and flow.
 The scatter diagrams of Space Mean Speed of
different classes of vehicles and corresponding
flows were plotted.

52.  To meet the several behavioral requirements like speed-
flow equations must be a decreasing and continuous
functions of flow and the speed-flow equations should
never intersect the x-axis (i.e. the predicted speed should
never reach precisely zero) , an exponential regression fit
was tried.
 The free-Speeds obtained from the intercept values of the
speed density relationships were compared with the free-
speeds obtained from the free-speed distributions for
different vehicle category

53. y = 34.69e-1E-04x
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400 1600
SPEED(KMPH)
TRAFFIC FLOW(PCU/HR)
FLOW vs SPEED(OVERALL)
OVERALL
Expon. (OVERALL)

54. y = -0.0337x + 29.695
R² = 0.0341
0
5
10
15
20
25
30
35
40
45
0 20 40 60 80 100 120 140
SPEED(KMPH)
TRAFFIC DENSITY(PCU/KM)
TRAFFIC DENSITY vs SPEED
COMBINED
Linear (COMBINED)

55. y = -0.1099x + 32.309
R² = 0.2976
0
5
10
15
20
25
30
35
40
45
0 20 40 60 80 100 120 140 160
SPEED(KMPH)
TRAFFIC DENSITY(PCU/KM)
TRAFFIC DENSITY vs SPEED
UP
Linear (UP)

56. y = 0.0838x + 24.419
0
10
20
30
40
50
60
70
0 20 40 60 80 100 120 140 160
SPEED(KMPH)
TRAFFIC DENSITY(PCU/KM)
TRAFFIC DENSITY vs SPEED
DOWN
Linear (DOWN)

57.  As the data was collected on particular road and
during a particular time, the observed data was
scattered within a particular zone of LOS leading to
difficulty in having the realistic value of jamming
density.

59.  Due to the presence of slow moving vehicle in
the traffic stream, platoon is formed.
 In such case, due to the opposing traffic,
vehicle in the platoon following the slow
moving one cannot overtake leading to the
formation of queue.
 At that point of time, vehicle in the queue will
try to find a gap opportunity to overtake the
vehicle ahead.

60. As a results speed of the follower vehicle will get
reduced until the overtaking operation is made.
 As speed is the most important criteria for determining
the capacity. The value of capacity will definitely be
reduced in the platoon which will ultimately lead to
change in level of service that is change in the quality of
the service.

61.  The present study is left with a further scope
of either developing a simulation model or
conducting the same survey work in a
congested road having same configuration i.e.
two lane two way so as to estimate the
capacity.