presented in MS class in 2018

1. Traffic Engineering
seminar
2018
1
ARBA MINCH UNIVERSITY INSTITUTE OF THECHNOLOGY
School of Post Graduate
DEPARTMENT OF ROAD AND TRANSPORT ENGINEERING

2. Highway Capacity
and Level of Service
Analysis
MULTILANE HIGHWAY

3. Contents
• INTRODUCTION
• CAPACITY
• LEVEL-OF-SERVICE (LOS)
• QUALITATIVE CATEGORIES FOR MULTILANE HIGHWAY
• BASE CONDITIONS FOR MULTILANE HIGHWAY
• DETERMINATION OF LEVEL OF SERVICE FOR MULTILANE
HIGHWAY
• ANALYSIS EXAMPLE
3

4. INTRODUCTION
• Capacity and Level of service are two related terms.
• Capacity analysis tries to give a clear understanding of how
much traffic a given transportation facility can accommodate.
• Level of service tries to answer how good is the present traffic
situation on a given facility.
• Level-of-Service is introduced by Highway Capacity Manual
(HCM)
• It was developed in 1950 by the transportation research board
of USA to denote the level of quality from a local condition
under different operation, characteristics and traffic volume.
• It provides some Analysis procedure to determine level of
service.
• It has developed the capacities standard and LOS measure for
various facilities.
4

5. • Capacity of a transport facility is defined as the maximum
number of vehicles, passengers, or the like, per unit time
which can be accommodated under given conditions with a
reasonable expectation of occurrence.
• The Highway Capacity Manual(2010) defines the capacity as
the maximum hourly rate at which persons or vehicles can
be reasonably expected to traverse a point during a given
time period, under prevailing roadway, traffic and control
conditions.
• EX. A capacity of 1900 vehicles per hour per lane for a
speed of 80kmph
CAPACITY
Definition
5

6. LEVEL-OF-SERVICE (LOS)
• The Highway Capacity Manual (2010) defines level of
service as a quantitative stratification of a performance
measure or performance measures that represent quality
of service.
• Level-of-Service(LOS) of a traffic facility is a concept
introduced to relate the quality of traffic service to a
given flow rate.
• Level of service (LOS) is a mechanism used to determine
how well a transportation facility is operating from a
traveler’s perspective.
Definition
6

7. Level of service
• Describes operational conditions within a traffic stream.
• Measure of “quality of service” Does not include safety
• Different measures for different facilities
• Based on traffic density
• Divides the quality of traffic into six levels from A (highest
Level/Best quality) to F (lowest Level/worst quality).
• Each traffic facility has its own unit for the capacity and
measure of effectiveness.
7
Continued

8. • two-lane highways
• multilane highways
• freeways and express ways.
• Urban streets
• Signalized intersections
• Pedestrians facilities
• Bicycle facilities etc...
 Roads with different operating characteristics are
8
Continued

9. Level of Service A
Travel conditions are completely free flow at operating
speed of 100 kmph .
 The only constraint on the operation of vehicles lies in
the geometric features of the roadway and individual
driver preferences.
Lane changing, merging and diverging maneuver within
the traffic stream is good, and minor disruptions to
traffic are easily absorbed without
an effect on travel speed.
Service volume is about 33 percent
of capacity ie 650 passenger cars
per hour per lane.
QUALITATIVE CATEGORIES FOR MULTILANE
HIGHWAYS
9

10. Level of Service B
 Travel conditions are at free flow. operating speeds at about
90 kmph.
 The presence of other vehicles is noticed but it is not a
constraint on the operation of vehicles as are the geometric
features of the roadway and individual driver preferences.
 Minor disruptions are easily absorbed, although localized
reduction in LOS are noted.
 Service volume will not exceed
50 percent of capacity ie 1000
passenger cars per hour per lane.
10
Continued

11. 11
Continued
Level of Service C
• Traffic density begins to influence operations.
• The ability to maneuver within the traffic stream is affected by
other vehicles.
• Travel speeds show some reduction when free-flow speeds
exceed 80 km/h.
• Minor disruptions may be expected to cause serious local
deterioration in service, and queues may begin to form.
• Stable flow with service volumes not exceeding 65 percent of
capacity ie 1300 passenger cars per
hour per lane.
• Operating speeds are at least 75 kmph.

12. Level of Service D
The ability to maneuver is severely restricted due to
congestion.
Travel speeds are reduced as volumes increase.
Minor disruptions may be expected to cause serious local
deterioration in service, and queues may begin to form.
Approaching unstable flow, with service volume up to 80
percent of capacity ie 1600 passenger cars per hour per lane.
Operating speeds are about 60 kmph
12
Continued

13. Level of Service E
• Operations are unstable at or near capacity ie 2000
passenger cars per hour per lane.
• Operating speeds are about 50 kmph.
• Densities vary, depending on the free-flow speed.
• Vehicles operate at the minimum spacing for which
uniform flow can be maintained.
• Disruptions cannot be easily dissipated and usually result
in the formation of queues and
the deterioration of
service to LOS F.
13
Continued

14. Level of Service F
A forced breakdown of flow occurs at the point where the
numbers of vehicles that arrive at a point exceed the
number of vehicles discharged or when forecast demand
exceeds capacity.
Queues form at the breakdown point, while at sections
downstream they may appear to be at capacity.
Operations are highly unstable, with vehicles experiencing
brief periods of movement followed
by stoppages.
Travel speeds within queues are
generally less than 50 km/h.
14
Continued

15. generally
• Level A
– High level of functional freedom.
•Level B
– Stable traffic although conditioned for the fastest vehicles.
•Level C
– Stable traffic although considerably conditioned.
•Level D
– Unstable traffic.
•Level E
– Flow near capacity, frequent stops.
•Level F
– Jammed road. The demand exceeds the capacity of the road.
15

16. 16

17. DETERMINATION OF LEVEL OF SERVICE
FOR MULTILANE HIGHWAY
•The determination of level of service for a multilane
highway involves four steps:
1. Determination of free-flow speed(FFS)
2. Determination of flow rate (Vp)
3. Determination of density(D):
4. Determination of level of service (LOS)
17

18. Methodology
18
Chart 1 Methodology for multi
lane highway (HCM2000)

19. 1. Lane widths are 3.6 m.
2. Lateral clearance is 1.8 m.
3. A minimum of 3.6 m of total lateral clearance in the
direction of travel.
• Clearances are measured from the edge of the
outer travelled lanes (shoulders included)
• lateral clearance of 1.8 m or greater are considered to
be equal to 1.8 m.
4. No direct access points along the highway.
5. A divided highway.
6. Only passenger cars in the traffic stream.
7. A free-flow speed of 90 km/h or more.
BASE CONDITIONS FOR MULTILANE
HIGHWAYS
19

20. 1. Determination of free-flow speed
• Free-flow speed (FFS)
FFS = BFFS − fLW − f LC − fM − fA
where, FFS is the estimated FFS (km/h),
BFFS= base FFS (km/h), For a given design speed 85th
percentile speed BFFS is obtained from interpolation.
f LW = adjustment for lane width, from Table 1 (km/h),
f LC = adjustment for lateral clearance, from Table 2 (km/h),
f M = adjustment for median type, from Table 3 (km/h), and
f A = adjustment for access points, from Table 4 (km/h)
20

21. Table 1. Adjustment for lane width Table 2. Adjustment for lateral clearance
Table 3. Adjustment to free flow speed
for median type
Table 4. Adjustment to free flow speed for
Access-point density
fLC
fM
fA
21
(Source: HCM, 2000)
fLW

22. Definition of some terms
• Hourly volume (V) The highest hourly volume within a 24-
hour period
• Peak-hour factor (PHF) The ratio of the hourly volume to
the peak 15 minute flow (V15) enlarged to an hourly value
• Service flow (SF) The peak 15 minute flow (V15) enlarged to
an hourly value
22
415 

V
V
PHF
415 VSF
2. Determination of Flow Rate

23. • The fifteen minute passenger-car equivalent flow rate
where,
- vp is the 15-min passenger-car equivalent flow rate (pc/h/ln),
- V is the hourly volume (veh/h),
- PHF is the peak-hour factor (in the range of 0.75 to 0.95),
- N is the number of lanes, in one direction.
- fp is the driver population factor=1 but can be reduced to 0.85
for the analysis of weekend and
- fHV is the heavy-vehicle adjustment factor,
pHV
p
ffNPHF
V
v


23

24. To determine fHV ,
where,
- fHV is the adjustment factor for heavy vehicles.
- ET and ER are the equivalents for trucks and buses
and for recreational vehicles(RVs), respectively, Table 5
- PT and PR are the proportion of trucks and buses, and
RVs, respectively,(expressed as a decimal fraction),
)1()1(1(
1


RRTT
HV
EPEP
f
Table 5. Passenger-car equivalent on extended general
highway segments(Source: HCM,2000) 24
Factor
Type of terrain
Level Rolling Mountainous
ET(Trucks and Buses) 1.5 2.5 4.5
ER( RVs) 1.2 2.0 4.0

25. 3. Determination of density(D):
where,
D is the density (pc/km/ln),
vp is the flow rate (pc/h/ln), and
S=FFS is the average passenger-car travel speed (km/h).
S
v
D
p

25

26. 26
Table 6: Level of Service criteria for a typical free flow speed of 100 kmph
proposed in HCM 2000
4. Determination of Level of Service
The level of service on a multilane highway can be
determined directly from Fig. 1 or Table-6 based on the free-
flow speed (FFS) and the service flow rate (Vp) in pc/h/ln.
Free
flow
speed
Criteria (LOS)
A
(LOS)
B
(LOS)
C
(LOS)
D
(LOS)
E
100Km/h Max. density (pc/km/ln) 7 11 16 22 25
Average speed (km/h) 100 100 98.4 91.5 88
Max. volume Capacity ratio 0.32 0.50 0.72 0.92 1.00
Max. service flow rate
(pc/h/ln)
700 1100 1575 2015 2200

27. Figure 1. Speed-flow curves with LOS criteria for multilane
highways
27

28. 28

29. ANALYSIS EXAMPLE
A segment of undivided four-lane highway on level terrain
has field-measured FFS 74.0km/h, lane width 3.4m, peak-
hour volume PHV 1,900veh/h, 13 percent trucks and
buses, 2 percent RVs, and 0.90 PHF. What is the peak-hour
LOS, speed, and density for the level terrain portion of the
highway?
29

30. Solution
The solution steps are given below:
i, Data given:
Level terrain,
Undivided 4 lane
 field measured FFS = 74 km/h,
 Lane width is 3.4 m
peak-hour volume = 1900 veh/h,
percent trucks and buses 13% PT = 0.13,
 percent RVs 2% PR = 0.02,
 PHF=0.90.
ii, Required a, s b, D c, LOS
30

31. 31
1. Determination of free flow speed(S):
 In this example the free flow speed (FFS) measured at the
field is given and hence no need to compute free flow
speed by indirect method.
FFS = BFFS − fLW − f LC − fM − fA
 Therefore, FFS = S = 74.0km/h.
NOTE:BFFS: from 85th percentile speed obtained by
interpolating between,
- 62.4 km/h 85th percentile speed is 64 km/h and
- 91.2 km/h when the 85th percentile speed is 96 km/h

32. Since fHV is unknown it is calculated from the equation
=> PT PR are given, ET and Ep from table 5,
Then
=> N=2 fp=1
pc/h/ln1129
)1935.029.0(
1900


pv
32
LOS can be calculated by knowing flow rate and free flow
speed. Flow rate (Vp) is calculated from the equation
pHV
p
ffNPHF
V
v


0.935
)12.1(02.0)15.1(13.01(
1
)1()1(1(
1





RRTT
HV
EPEP
f
2. Determination of flow rate (Vp):

33. 3. Determination of density(D):
The density of flow is computed from the equation
3.15
74
1129

S
v
D
p
33
74
1129
4. Determination of LOS:
LOS determined from the speed-flow diagram figure 1. LOS = C.

34. Conclusion
• Different road facilities have different capacity
standard and LOS measures depending on their
function.
• Different road facilities will have different analysis
procedure to determine level of service.
• Density method of analysis can be used to determine
level of service of multilane highway.
Gizaw Mk 34

35. Reference
• TRB (2000 ) High way capacity manual.
• Martin Rogers (2003) HIGHWAY ENGINEERING, Dublin Institute of
Technology Ireland.
• Nicholas J. Garber and Lester A. Hoel (2009) Traffic and Highway
Engineering, Fourth Edition
• Tom V. Mathew, (2014) Transportation Systems Engineering. IIT Bombay
• CA O’flaherty (2003) Transport planning and traffic engineering.
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