3-1

Section 3 Traffic Capacity Analysis

3.1 Capacity Analysis Methodology The capacity analysis methodology is based on the concepts and procedures

of the 2000 Highway Capacity Manual (HCM). The HCM documents

procedures and guidelines for the measurement, analysis, and interpretation

of data quantifying highway capacity and quality of service. The primary

result of capacity analysis is the assignment of levels of service to traffic

facilities under different traffic flow conditions. The concept of Level of

Service (LOS) is defined as a qualitative measure describing the operational

conditions within the traffic stream and their perception by motorists and/or

passengers. A level-of-service definition provides an index to quality of

traffic flow in terms of such factors as speed, travel time, freedom to

maneuver, traffic interruptions, comfort, convenience, and safety.

Six levels of service are defined for signalized intersections. They are given

letter designations from A to F, with LOS A representing the best operating

conditions and LOS F the worst. Levels of service for signalized intersections

are calculated using the operational analysis methodology of the HCM.

The methodology for signalized intersections assesses the effects of signal

type, timing, phasing, and progression along with vehicle mix and

geometrics on average stopped delay. Accordingly, level of service

designations for signalized intersections are based on the criterion of

calculated average stopped delay per vehicle. Delay is a measure of driver

discomfort, frustration, fuel consumption, and lost travel time.

Table 3.1-1 summarizes the relationship between level of service and average

stopped delay for signalized intersections.

Table 3.1-1 Level of Service for Signalized Intersections

Level of Service Signalized Intersection Criteria Average Stopped Delay (Seconds per Vehicle)

A 10

B 10 to 20

C 20 to 35

D 35 to 55

E 55 to 80

F > 80

Source: Highway Capacity Manual, HCM2000; Transportation Research Board;

Washington, DC; 2000. Page 16-2.

Section 3 Traffic Capacity Analysis

3-3

For signalized intersections, these delay criteria may be applied in assigning

level-of-service designations to individual lane groups, to individual

intersection approaches, or to the entire intersection.

3.2 Existing and Future No-Build Traffic Operations

Levels of service were calculated for the signalized intersection of Route 30

and Route 27 using the industry accepted Synchro 5.0 software package. The

analysis was performed for the year 2002 and the design years of 2017 and

2022. The existing and No-Build conditions maintain the current traffic

control, signal phasing operation and lane usage at the intersection as

described in Sections 2.1 (Physical Layout) and 2.2 (Traffic Signals). The

results of the analysis are included in Table 3.2-1 and include the morning

and evening peak hours. The signalized intersection experiences significant

delays, showing a LOS D in the AM peak hour and a LOS E in the PM

peak hour. Without improvements, the intersection level of service will

decrease to F for both the AM and PM peak hours. The existing and future

No-Build analyses are summarized in Table 3.2-1 and detailed traffic

analysis is included in Appendix I.

Section 3 Traffic Capacity Analysis

3-3

Tabl

e 3.

2-1

Level

o

f Ser

vic

e - R

ou

te 30

a

t Ro

ute

27

Ex

istin

g 20

17 Fu

ture

N

o-Bu

ild

2022

Fu

ture

N

o-Bu

ild

Loca

tion

V

/C1

Del

ay2

LO

S3

95%

Queue4

V/C

D

elay

LOS

95%

Queue

V/C

D

elay

LO

S 95

%

Queu

e

Mo

rnin

g Pe

ak

Hou

r

Ro

ute

27

N

B L5

0.

95

65.4

E #1

59

1.60

20

1.6

F #1

806

1.73

22

1.0

F #1

97

Ro

ute

27

N

B TR

0.

78

19.6

B #3

06

0.97

40

.0

D

#427

1.

05

58.5

E #4

75

Ro

ute

27

SB

LT

R 1.

27

123.

0 F

#508

2.

67

312.

6 F

#646

4.

13

371.

1 F

#785

Ro

ute

30

EB

LT

R

0.82

16

.7

B #3

76

1.07

58

.7

E #5

81

1.17

90

.5

F #6

52

Ro

ute

30

W

B LT

R 0.

81

23.7

C #2

76

1.15

89

.3

F #4

07

1.31

13

4.0

F #4

60

Over

all

51

.0

D

139.

5 F

177.

6 F

Eve

nin

g Pe

ak

Hou

r

Ro

ute

27

N

B L

0.85

42

.3

D

#162

1.

37

155.

2 F

#226

1.

64

205.

8 F

#206

Ro

ute

27

N

B TR

0.

96

37.8

D

#433

1.

20

102.

1 F

#583

1.

30

129.

6 F

#643

Ro

ute

27

SB

LT

R 1.

70

213.

3 F

#508

4.

24

373.

5 F

#660

4.

98

388.

9 F

#724

Ro

ute

30

EB

LT

R

0.97

34

.7

C #4

97

1.31

13

0.0

F #6

99

1.45

16

4.9

F #7

77

Ro

ute

30

W

B LT

R 0.

83

23.2

C #3

23

1.15

88

.6

F #4

70

1.30

13

0.9

F #5

27

O

ver

all

72

.1

E

16

9.4

F

20

0.7

F

1 V

olu

me

to Ca

paci

ty Ra

tio

2 D

elay

in

se

conds

3 Le

vel o

f Ser

vic

e 4

Queu

e in

fe

et

5 L

= Le

ft Tu

rn, T

= Th

ru, R

= Ri

ght;

LTR

or

oth

er co

mbi

nat

ion is

a sh

ared

la

ne

6 #

indi

cate

s th

at th

e volu

me

for

the

95th pe

rcen

tile

exce

eds

capa

city

.

7 O

ver

all L

evel

o

f Ser

vic

e is

the

Inte

rsec

tion Le

vel

o

f Ser

vic

e.