This document discusses concepts related to transportation capacity analysis including: - Definitions of level of service (LOS) categories A through F and their characteristics. - How capacity is defined as the maximum hourly rate of vehicles that can pass a point under prevailing conditions. - Procedures from the Highway Capacity Manual (HCM) for calculating capacity for basic freeway sections and the impacts of factors like lane width, lateral clearance, and free flow speed. - The relationships between capacity, LOS, and transportation design and how capacity analysis can inform design.

1. 1
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Capacity Analysis
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Objectives
 Review LOS definition and determinants
 Define capacity and relate to “ideal”
capacities
 Review calculating capacity using HCM
procedures for basic freeway section
 Focus on relations between capacity, level-of-
service, and design

2. 2
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Level of Service (LOS)
• Concept – a qualitative measure describing
operational conditions within a traffic stream
and their perception by drivers and/or
passengers. (speed, travel time, free to maneuver, comfort)
• 6 LOS (A to F)
• Levels represent range of operating conditions
defined by measures of effectiveness (MOE)
such as (Density, Speed, V/C) .
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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LOS A (Freeway)
• Free flow conditions.
• Vehicles are unimpeded
in their ability to
maneuver within the
traffic stream.
• Incidents and
breakdowns are easily
absorbed.

3. 3
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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LOS B (Stable Flow)
• Flow reasonably free
• Ability to maneuver is slightly
restricted
• General level of physical and
psychological comfort provided
to drivers is high
• Effects of incidents and
breakdowns are easily
absorbed
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
6
LOS C (Stable Flow)
• Flow at or near Free Flow
Speed
• Freedom to maneuver is
noticeably restricted
• Lane changes more difficult
• Minor incidents will be
absorbed, but will cause
deterioration in service
• Queues may form behind
significant blockage

4. 4
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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LOS D (Unstable Flow)
• Speeds begin to decline with
increasing flow
• Freedom to maneuver is
noticeably limited
• Drivers experience physical
and psychological
discomfort
• Even minor incidents cause
queuing, traffic stream
cannot absorb disruptions
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
8
LOS E = Capacity
• Capacity
• Operations are volatile, virtually
no usable gaps
• Vehicles are closely spaced
• Disruptions such as lane
changes can cause a disruption
wave that propagates
throughout the upstream traffic
flow
• Cannot dissipate even minor
disruptions, incidents will cause
breakdown

5. 5
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
9
LOS F (Forced Flow)
• Breakdown or forced flow occurs
when:
• Traffic incidents cause a
temporary reduction in
capacity
• At points of recurring
congestion, such as merge or
weaving segments
• In forecast situations,
projected flow (demand)
exceeds estimated capacity
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
Different levels of Service
10

6. 6
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Design Level of Service
This is the desired quality of traffic conditions from a driver’s
perspective (used to determine number of lanes)
• Design LOS is higher for higher functional classes
• Design LOS is higher for rural areas
• LOS is higher for level/rolling than mountainous terrain
• Other factors include: adjacent land use type and
development intensity, environmental factors, and
aesthetic and historic values
• Design all elements to same LOS (use HCM to
analyze)
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Design Level of Service (LOS)

7. 7
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Capacity – Defined
• Capacity: Maximum hourly rate of vehicles or
persons that can reasonably be expected to
pass a point, or traverse a uniform section of
lane or roadway, during a specified time period
under prevailing conditions (traffic and roadway)
• Different for different facilities (freeway, multilane,
2-lane rural, signals)
• Why would it be different?
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Ideal Capacity
• Freeways: Capacity
(Free-Flow Speed)
2,400 pcphpl (70 mph)
2,350 pcphpl (65 mph)
2,300 pcphpl (60 mph)
2,250 pcphpl (55 mph)
• Multilane Suburban/Rural
2,200 pcphpl (60 mph)
2,100 pcphpl (55 mph)
2,000 pcphpl (50 mph)
1,900 pcphpl (45 mph)
• 2-lane rural – 2,800 pcph
• Signal – 1,900 pcphgpl

8. 8
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
Multilane Highways
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
17
Multilane Highways
• Assumptions (Ideal Conditions, all other
conditions reduce capacity):
• Only passenger cars
• No direct access points
• A divided highway
• FFS > 60 mph
• Represents highest level of multilane rural and
suburban highways

9. 9
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
Base Conditions
• 12-ft lane widths
• A minimum of 12 ft of total lateral clearance in the
direction of travel. Clearances are measured from the
edge of the traveled lanes (shoulders included) and of 6
ft or greater are considered to be equal to 6 ft
• No direct access points along the highway
• A divided highway
• Only passenger cars in the traffic stream
• A free-flow speed of 60 mph or more
• 7. Driver population consisting primarily of commuters
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Multilane Highways
• Intended for analysis of uninterrupted-flow
highway segments
• Signal spacing > 2.0 miles
• No on-street parking
• No significant bus stops
• No significant pedestrian activities

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‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Source: HCM, 2000
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
21
Source: HCM, 2000
Step 1: Gather data
Step 2: Calculate capacity (Supply)

11. 11
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
22
Source: HCM, 2000
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
23
Source: HCM, 2000

12. 12
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
24 Source: HCM, 2000
Lane Width
• Base Conditions: 12 foot lanes
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
25
Source: HCM, 2000
Lane Width (Example)
How much does use of 10-foot lanes decrease free flow speed?
Flw = 6.6 mph

13. 13
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Lateral Clearance
• Distance to fixed objects
• Assumes
• >= 6 feet from right edge of travel lanes to
obstruction
• >= 6 feet from left edge of travel lane to object
in median
Source: HCM, 2000
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
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Lateral Clearance
TLC = LCR + LCL
TLC = total lateral clearance in feet
LCR = lateral clearance from right edge of travel
lane
LCL= lateral clearance from left edge of travel lane
Source: HCM, 2000

14. 14
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
28
Source: HCM, 2000
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
29
Example: Calculate lateral clearance adjustment for a 4-lane divided highway with milepost
markers located 4 feet to the right of the travel lane.
Source: HCM, 2000
TLC = LCR + LCL = 6 + 4 = 10
Flc = 0.4 mph

15. 15
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
30
Accounts for friction between opposing directions of
traffic in adjacent lanes for undivided
No adjustment for divided, fm = 0
Source: HCM, 2000
TWLTLs: two way left turn lanes
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
31
Fa accounts for interruption due to access points along the facility
Example: if there are 20 access points per mile, what is the
reduction in free flow speed?
Fa = 5.0 mph

16. 16
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
32
Estimate Free flow Speed
BFFS = free flow under ideal conditions
FFS = free flow adjusted for actual conditions
From previous examples:
FFS = 60 mph – 6.6 mph - 0.4 mph – 0 – 5.0 mph = 48 mph
( reduction of 12 mph)
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
33 Source: HCM, 2000
Step 3: Estimate demand

17. 17
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
34
Calculate Flow Rate
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
35
f(hv) General Grade Definitions:
 Level: combination of alignment (horizontal and vertical) that
allows heavy vehicles to maintain same speed as passenger
cars (includes short grades 2% or less)
 Rolling: combination that causes heavy vehicles to reduce
speed substantially below P.C. (but not crawl speed for any
length)
 Mountainous: Heavy vehicles at crawl speed for significant
length or frequent intervals
 Use specific grade approach if grade less than 3% is more
than ½ mile or grade more than 3% is more than ¼ mile)

18. 18
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
36
Passenger Car Equivalent (Unit):
PCE or PCU
• Passenger Car Equivalent (PCE), is a metric used to assess traffic-
flow rate on a highway.
• A PCE is essentially the impact that a mode of transport has on traffic
variables (such as headway, speed, density) compared to a single car.
• Typical values of PCE (or PCU) are:
• private car (including taxis or pick-up) 1
• motorcycle 0.5
• bicycle 0.2
• horse-drawn vehicle 4
• bus, tractor, truck 3.5
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
37
f(hv) General Grade Definitions:
 Level: combination of alignment (horizontal and vertical) that
allows heavy vehicles to maintain same speed as passenger
cars (includes short grades 2% or less)
 Rolling: combination that causes heavy vehicles to reduce
speed substantially below P.C. (but not crawl speed for any
length)
 Mountainous: Heavy vehicles at crawl speed for significant
length or frequent intervals
 Use specific grade approach if grade less than 3% is more
than ½ mile or grade more than 3% is more than ¼ mile)

19. 19
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
38
Example: for 10% heavy trucks on rolling terrain,
what is FHV?
For rolling terrain, ET = 2.5
FHV = _________1_______ = 0.87
1 + 0.1 (2.5 – 1)
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
39
f(hv) General Grade Definitions:
 Level: combination of alignment (horizontal and vertical) that
allows heavy vehicles to maintain same speed as passenger
cars (includes short grades 2% or less)
 Rolling: combination that causes heavy vehicles to reduce
speed substantially below P.C. (but not crawl speed for any
length)
 Mountainous: Heavy vehicles at crawl speed for significant
length or frequent intervals
 Use specific grade approach if grade less than 3% is more
than ½ mile or grade more than 3% is more than ¼ mile)

20. 20
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
40
Peak Hour Factor (PHF)
• 𝑃𝐻𝐹 =
𝐻𝑜𝑢𝑟𝑙𝑦 𝑉𝑜𝑙𝑢𝑚𝑒
𝑃𝑒𝑎𝑘 𝑅𝑎𝑡𝑒 𝑜𝑓 𝐹𝑙𝑜𝑤 𝑤𝑖𝑡ℎ𝑖𝑛 𝑡ℎ𝑒 ℎ𝑜𝑢𝑟
If 15-minute periods are used, the PHF is computed as:
• 𝑃𝐻𝐹 =
𝑉
4𝑥𝑉15
V = peak-hour volume (vph)
V15 = volume during the peak 15 minutes of
flow (veh/15 minutes)
Typical peak-hour factors for freeways range between 0.80 and 0.95.
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
41
Source: HCM, 2000
Step 4: Determine LOS
Demand Vs. Supply

21. 21
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
42
• Calculate vp
• Example: base volume is 2,500 veh/hour
• PHF = 0.9, N = 2
• fhv from previous, fhv = 0.87
• Non-familiar users, fp = 0.85
vp = _____2,500 vph _____ = 1878 pcphpl
0.9 x 2 x 0.87 x 0.85
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
43
Calculate Density
Example: from previous
D = _____1878 vph____ = 39.1 pc/mi/lane
48 mph

22. 22
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
44
LOS = E
Also, D = 39.1 pc/mi/ln, LOS E
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
45
Design Decision
• What can we change in a design to provide an
acceptable LOS?
• Lateral clearance (only 0.4 mph)
• Lane width
• Number of lanes

23. 23
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
46 Source: HCM, 2000
Lane Width (Example)
How much does use of 10 foot lanes decrease free flow speed?
Flw = 6.6 mph
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
47
Recalculate Density
Example: for previous (but with wider lanes)
D = _____1878 vph____ = 34.1 pc/mi/lane
55 mph

24. 24
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
48
LOS = E
Now D = 34.1 pc/mi/ln, on border of LOS E
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
49
• Recalculate vp, while adding a lane
• Example: base volume is 2,500 veh/hour
• PHF = 0.9, N = 3
• fhv from previous, fhv = 0.87
• Non-familiar users, fp = 0.85
vp = _____2,500 vph _____ = 1252 pc/ph/pl
0.9 x 3 x 0.87 x 0.85

25. 25
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬
50
Calculate Density
Example: from previous
D = _____1252 vph____ = 26.1 pc/mi/lane
48 mph
‫والتكنولوجيا‬ ‫للهندسة‬ ‫العالي‬ ‫مصر‬ ‫معهد‬–‫المدنية‬ ‫الهندسة‬ ‫قسم‬-‫المنصورة‬ 51
LOS = D
Now D = 26.1 pc/mi/ln, LOS D (almost C)