Problem 3: Application of HCM Chapters to Arterial
and Highway Segments
Printable Version
The HCM procedural
chapters (Chapter 15 for arterials and Chapter 20 for two-lane highways)
provide a detailed computational methodology for estimating the level of
service on these two types of facilities. In this problem, we will apply those
procedures to compute the performance measures that determine the LOS
for thefacilities defined by the three sections. We will also compare the results with those of
the planning level analyses performed in Problem 2.
The following
sub-problems are included in Problem 3. Each sub-problem deals with a
separate section of Krome Avenue.
Sub-problem 3a. North Section (Class I Two-lane Highway
facility)
Sub-problem 3b. Center Section (Class I or II Two-lane Highway
facility)
Sub-problem 3c. South Section (Class I Signalized Arterial
facility)
Each of these sub-problems will be
discussed separately.
Before we
begin to compute the operational parameters of the various facilities
along Krome Avenue, consider the following key issues:
|
What (if
any) potential issues were identified during the planning level
analysis that may require mitigation? |
|
What
benefit was derived through the planning level analysis in this case
study? |
Discussion:
Take a few minutes to consider these questions. When you are ready to
continue, click continue below to proceed.
[
Back ]
to Sub-Problem 2c [ Continue
] to Sub-problem 3a |
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Sub-problem 3a:
Analysis of the North Section of Krome
Avenue (Class I Two-lane Highway Facility)
Step 1. Setup
In this sub-problem, we will replace the
assumptions used in our planning analysis with field data. We will
then be able to compare the HCM planning analysis from Problem 2 with the
operations analysis presented in this problem.
Consider:
|
What is the difference between
the planning and operations analysis? |
| What additional data will
be applied in the operations procedure?
|
Discussion:
Take
a few minutes to consider these questions. Click continue when you are
ready to proceed. [ Back ] [
Continue
] with Sub-Problem 3a |
Page Break
Sub-problem 3a: Analysis of the North Section of Krome Avenue (Class I
Two-lane Highway Facility)
In sub-problem 2a, we produced an estimate
of the LOS for the facility defined by the north section of Krome Avenue, assuming that it operates
with the characteristics of typical two-lane highways of the same class. In
this sub-problem, we will examine the assumptions and substitute observed
values for this section to apply the more detailed operational procedures.
What is the
difference between the planning and operations level analyses?
It is important to recognize the difference between the planning and
operational level procedures. The operational procedure estimates the level
of service from computed performance measures that are compared against
established LOS thresholds for those measures. The two performance measures
are percent time spent following (PTSF) and
average travel speed (ATS). The
LOS thresholds for these measures are shown in Exhibit 3-17 for a Class I
two-lane highway. For this highway class, the more critical
of the two measures will determine the LOS.
Exhibit 3-17. LOS Thresholds for Class I Two-Lane
Highways |
LOS |
Percent
Time-Spent-Following |
Average Travel Speed (mph) |
A |
<35 |
>55 |
B |
>35-50 |
>50-55 |
C |
>50-65 |
>45-50 |
D |
>65-80 |
>40-45 |
E |
>80 |
<40 |
The planning level procedure presented in HCM Chapter 12 was derived from
the operational procedure, assuming typical values for all operating
parameters. The service volume table in HCM Exhibit 12-15 was produced by
applying the operational procedure repetitively with different volumes and
noting the volume levels at which the LOS changed from one value to the
next. As such, the service volume table results should be identical to the
operational level results, but only when the same operating parameters are
applied to both procedures.
For example, the service volume tables presented in the HCM and used within
the planning analysis assumes 14% trucks and buses. Data collected for Krome Avenue indicates the corresponding value for Krome Avenue is 27%.
Similarly, the default
peak hour factor for rural conditions assumed in the HCM is 0.88, whereas the actual measured PHF is 0.94. The differences
between these values will cause the results of the two methods to depart
from each other; and the operational level results must be considered more
accurate, because they are based on actual field data instead of assumptions
that do not apply to the facility under study.
Planning-level analyses are appropriate when operational
parameters do not exist (for example, in a future-year analysis) or cannot
be feasibly obtained. In such circumstances, detailed analysis such as queue
length estimates are not appropriate because the quality of the available
data does not support this level of analysis. [ Back ] [
Continue ] with Sub-Problem 3a |
Page Break
Sub-problem 3a: Analysis of the North Section of Krome Avenue (Class I
Two-lane Highway Facility)
The procedures given
in HCM Chapter 20 will be applied to the facility defined by this section of Krome Avenue.
What is the
additional data that will be applied in the operations procedure?
The
additional data (i.e., beyond the sub-problem 2a
requirements) include:
|
percent
trucks
|
|
directional
split
|
| percent
no passing zones
|
| shoulder
width
|
| lane
width
|
| PHF
|
|
access points per mile
|
| segment
length
|
The last item, segment
length, is not actually required for estimation of LOS, but it is used for
calculation of travel time and vehicle-miles of travel. All of these data
items with their associated sources and assumptions were discussed in the Getting Started section of this case
study.
[
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] with Sub-Problem 3a |
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Sub-problem
3a: Analysis of the North Section of Krome Avenue (Class I
Two-Lane Highway Facility)
Step 2. Results
The table below compares the results from the planning level
analysis in sub-problem 2a with the
operational level analysis. This table shows the values assumed by the
service volume tables for all parameters, as compared with the values that
apply to this facility. It shows the computations and results for both
methods. The average travel speed (ATS) was computed as 45.2 mph, which suggests LOS C. The
percent time-spent-following (PTSF)
was computed as 66.9%, which suggests LOS D.
So, the resulting LOS was based on the PTSF and was found to be LOS D. This result was identical to the LOS estimate given by the service volume
tables. The interpretation of the agreement between the two procedures is
that the sum total of all of the differences between the assumed parameters
and the site-specific parameters for this facility was not sufficient to
produce a difference in the estimated level of service.
Exhibit 3-18. Sub-Problem 2a Planning Analysis vs. Sub-Problem 3a
Operational Analysis |
Input Data |
Sub-problem 2a |
Sub-problem 3a |
Terrain |
Level |
Level |
Base Free Flow Speed |
N/A |
56.5 |
Access point / mile |
N/A |
1 |
Shoulder Width |
N/A |
3 |
Free Flow Speed |
55 |
55 |
Directional Split |
60/40 |
62/38 |
Percent Trucks |
14 |
27 |
Percent RV’s |
4 |
Included in Truck % |
Percent No Passing |
20 |
18 |
PHF |
N/A |
0.94 |
Design Hour Volume |
1,110 |
1,110 |
Comparison of Results |
Table
Thresholds |
|
Computations |
LOS A |
--- |
|
ATS = 45.2 mph |
LOS B |
330 |
PTSF = 66.9 |
LOS C |
870 |
v/c = 0.38 |
LOS D |
1,460 |
|
LOS E |
2,770 |
Estimated LOS: |
D |
D |
[ Back ] [
Continue ] with Sub-Problem 3a |
Page Break
Sub-problem 3a: Analysis of the North Section of Krome Avenue (Class I
Two-lane Highway Facility)
The question of base free flow speed deserves further discussion. The
service volume tables deal in 5 mph increments of free flow speed. The
operational method requires a specified base free flow speed, which is
adjusted to reflect the effects of the specified shoulder width and the
number of access points per mile in computing the actual free flow speed. In the course of the computations, the actual free flow speed was adjusted
downwards in this case by 1.5 mph. So, to promote a fair comparison, the
base free flow speed was specified as 56.5 mph, to produce the same free
flow speed of 55 mph that was used by the service volume tables. This
modification to the base free would not normally be recommended as a sound
analytical practice. It was applied in this sub-problem to facilitate
comparison between the planning and operational level procedures.
The HCM Chapter 20
procedure has given an overall level of service for this facility based on
the performance measures for two-lane roadways. This procedure does not
recognize any intersection-related problems. Therefore, a complete
assessment of the facility requires a check of all intersections to ensure
that problems are not being overlooked. The proper procedures to apply to
intersections are found in HCM Chapter 16 (signalized) and HCM Chapter 17 (unsignalized). The details of the intersection analyses will not be presented here; however,
it was found that two intersections experienced problems that will require
further attention.
|
The intersection
with Okeechobee Rd operates under two-way stop control (TWSC). This is a
T intersection in which Krome Avenue is stopped at its northern terminus. The northbound approach here is oversaturated, and mitigation
measures will be required. The alternative measures will be discussed in
Problem 4. |
|
The southern
boundary of this section includes conditions that warrant further
consideration. In this case,
the cross street movements at Kendall Road are oversaturated. Mitigation measures will be
discussed in
Problem 5. |
[
Back ] [
Continue ] to sub-problem
3b |
Page Break
Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
Step 1. Setup
In this sub-problem, we will replace the
assumptions used in our planning analysis with field data for the facility
defined by the center
section of Krome Avenue. We will
then be able to compare the HCM planning analysis to the operations analysis
for this example, based on what is known about
the assumptions made in the planning analysis verses the actual conditions
along Krome Avenue.
Consider:
|
What are the differences in analyses for Class I and II
facilities? |
| What LOS do you expect the results of the analysis to
show? |
Discussion:
Take
a few minutes to consider these questions. Click continue when you are
ready to proceed. [
Back ] to Sub-Problem 3a [
Continue
] with Sub-Problem 3b |
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Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
The
procedures given in HCM Chapter 20 will be applied to the facility defined
by this section. It was
determined in
sub-problem 1b
that
this facility has characteristics that could normally be associated with
both Class I and Class II two-lane highways. Therefore, the analysis will
be repeated for both Class I and Class II facilities, and the results will
be compared. The results will also be compared with those of the planning
level analysis performed in
sub-problem 2b.
Exhibit 3-19. LOS Criteria for Two-Lane Highways |
|
Class I |
Class II |
LOS |
Percent Time- Spent-Following |
Average Travel Speed (mph) |
Percent Time-Spent-Following |
A |
<35 |
>55 |
<40 |
B |
35.1-50 |
50.1-55 |
40.1-55 |
C |
50.1-65 |
45.1-50 |
55.1-70 |
D |
65.1-80 |
41.1-45 |
70.1-85 |
E |
>80 |
<41 |
>85 |
What are the differences in analyses
for Class I and II facilities? We will begin with a
discussion of the differences in the LOS estimation procedures for Class I
and II facilities.
As we pointed out in
sub-problem 3a, the key performance measures for two-lane highways
are the percent time spent following (PTSF) and the average travel speed (ATS).
The LOS thresholds for these measures are shown in Exhibit 3-19 for both facility Classes.
On a Class I facility,
the more critical of the two measures will determine the LOS. On a Class II
facility, only the PTSF is considered, and the LOS thresholds for Class II
are shifted upwards by 5 percentage points from Class I to reflect the lower
driver expectation on a Class II highway. For example, the threshold for LOS
E for Class I facilities is 80% and for Class II facilities it is 85%. One important point is that the
performance measures will be computed in exactly the same way for both
classes. In other words, the Class that you specify will not affect either
the PTSF or the ATS. Only the thresholds will be applied differently. [
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] with Sub-Problem 3b |
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Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
What LOS do you expect the results of the analysis to show? This is
difficult to determine because of the differences in the criteria used
between the two class types. As we will see in the next few pages, the
various criteria lead to different estimates for LOS.
Which factor do you expect to
determine the level of service on a Class I Facility? In a vast majority of
cases involving Class I two-lane roadways, the LOS will be determined by the
PTSF. On the rare occasion that the ATS emerges as the determining factor,
it is a good idea to revisit the question of whether this really should be
considered as a Class I facility. The ATS will generally be the critical
determinant of LOS only when the free flow speed is low. A low free flow
speed is frequently the result of the same factors that would reduce the
driver’s expectation of a high speed. As a Class I facility, the operation
of this section of Krome Avenue would probably be considered unacceptable at
LOS E. As a Class II facility it would fall into LOS D, only 1/10 of a PTSF percentage point away from LOS C (70.0% vs 70.1%). This raises
a separate but frequently stated point about the value of judgment in
dealing with thresholds.
[
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] with Sub-Problem 3b |
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Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
Step
2. Results
Exhibit 3-20
compares the results from the planning level analysis in
sub-problem 2b with
the operational level analysis. It shows the values assumed by the
service volume tables for all parameters, as compared with the values that
apply to this facility. It also shows the computations and results for both
methods. The ATS was computed as 39.3 mph. The PTSF was computed as 70.1%.
If this facility were
designated as a Class I highway, the ATS would be the critical determinant
of LOS, producing a value of E. The PTSF would have suggested LOS D. If
the designation were changed to Class II, the ATS would be eliminated as a
determinant of LOS, and the PTSF would establish LOS D.
Exhibit 3-20. Center Section: Comparison of Planning and Operational
Level Analysis Results |
Input Data |
Table
Assumptions
HCM Chapter 10
Sub-problem 2b |
Field
Observations
HCM Chapter 20
Sub-problem 3b |
Terrain |
Level |
Level |
Base Free Flow Speed |
N/A |
53.1 mph |
Access Points Per Mile |
N/A |
2 |
Shoulder Width |
N/A |
3 |
Free Flow Speed |
50 mph |
50 |
Directional Split |
60/40 |
57/43 |
Percent Trucks |
14 |
26 |
Percent RV's |
4 |
Included in
Percent Trucks |
Percent No Passing |
20 |
8 |
PHF |
N/A |
0.91 |
Design Hour Volume |
1,190 |
1,190 |
|
Comparison
of Results |
Table
Thresholds |
Computations |
LOS A: |
--- |
ATS=39.3
PTSF=70.1
v/c=0.42 |
LOS B: |
--- |
LOS C: |
330 |
LOS D: |
1,000 |
LOS E: |
2,770 |
Estimated LOS |
Class I Facility |
E |
E |
Class II Facility |
N/A |
D |
[ Back ] [
Continue ] to Sub-Problem
3c |
Page Break
Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
The
decision on class designation rests solely with the operating agency. The
purpose of this Guide is to point out the factors that should be taken into
consideration and their relationship to the HCM procedures. Therefore, the
question of whether this portion of Krome Avenue should be a Class I or II
facility will remain open.
Before we leave this
sub-problem, we should take a look at how the operational analysis results
compared with the service volume table results from
sub-problem 2b. The comparison is
evident in
Exhibit 3-20. The bottom line is that, for a Class I facility the same estimation
of LOS was produced by both procedures. While the LOS was improved for a
Class II facility for the reasons just stated, it is not possible to compare
this result with the service volume tables, because those tables are limited
in scope to Class I facilities.
One last point: the
base free flow speed was adjusted upwards to produce the same actual free
flow speed used in the service volume tables to facilitate the comparison of
the planning and operational level analyses. This topic was explained in
detail in
sub-problem 3a. The amount
of the adjustment in this case was 3.1 mph, resulting in a base free flow
speed of 53.1 mph in the table on the previous page.
[
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] with Sub-Problem 3b |
Page Break
|
|
Exhibit 3-20. Center Section: Comparison of Planning and Operational
Level Analysis Results |
Input Data |
Table
Assumptions
HCM Chapter 10
Sub-problem 2b |
Field
Observations
HCM Chapter 20
Sub-problem 3b |
Terrain |
Level |
Level |
Base Free Flow Speed |
N/A |
53.1 mph |
Access Points Per Mile |
N/A |
2 |
Shoulder Width |
N/A |
3 |
Free Flow Speed |
50 mph |
50 |
Directional Split |
60/40 |
57/43 |
Percent Trucks |
14 |
26 |
Percent RV's |
4 |
Included in
Percent Trucks |
Percent No Passing |
20 |
8 |
PHF |
N/A |
0.91 |
Design Hour Volume |
1,190 |
1,190 |
|
Comparison
of Results |
Table
Thresholds |
Computations |
LOS A: |
--- |
ATS=39.3
PTSF=70.1
v/c=0.42 |
LOS B: |
--- |
LOS C: |
330 |
LOS D: |
1,000 |
LOS E: |
2,770 |
Estimated LOS |
Class I Facility |
E |
E |
Class II Facility |
N/A |
D |
|
|
Page Break
Sub-problem 3b: Operational
Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane
Highway Facility)
The
HCM Chapter 20 procedure has given an overall level of service for this
facility, based on the performance measures for two-lane roadways. This
procedure does not recognize any intersection-related problems. Therefore, a
complete assessment of the facility requires a check of all intersections to
ensure that problems are not being overlooked. The proper procedures to
apply to intersections are found in HCM Chapter 16 (signalized) and 17 (unsignalized). The details of the intersection analyses will not be presented here.
Apart from the northern
boundary at Kendall, which was mentioned in
sub-problem 3a, the only operational problem was found at
Biscayne. This is an unsignalized intersection with the cross street operating under
stop control. Signalization will be required to overcome this deficiency.
The signalized intersection analysis will not be
covered in this case study.
[
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Sub-problem 3c: Operational
Analysis of the South Section of Krome Avenue (Class I Signalized Arterial
Facility)
Step 1. Setup
In this sub-problem, we will replace the
assumptions used in our planning analysis with field data. We will
then compare the results of the HCM planning analysis to the results of the
operations analysis. Based on assumptions made in the planning analysis of problem 2 versus the
actual conditions of Krome Avenue described in this case study, do you think
the results of the two analyses will be similar? Better or worse?
Consider:
|
What additional data will
be applied in the operations procedure?
|
| What are the factors that are used to determine urban
street LOS? |
Discussion:
Take
a few minutes to consider these questions. Click continue when you are
ready to proceed. [
Back ] to Sub-Problem 3b [
Continue
] with Sub-Problem 3c |
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Sub-problem 3c: Operational
Analysis of the South Section of Krome Avenue (Class I Signalized Arterial
Facility)
In
sub-problem 2c,
we have produced an estimate of the LOS for the facility defined by the
facility defined by the south section of Krome
Avenue, using the service volume tables in HCM Exhibit 10-7. These tables
assume that the facility operates with the characteristics of typical
signalized arterials of the same class. In this sub-problem, we will examine
the assumptions and substitute observed values from the field to apply the
more detailed operational procedures.
What additional data will
be applied in the operations procedure?
The procedures given in
HCM Chapter 15 will be applied to this facility. The additional data (i.e.,
beyond the
sub-problem 2c requirements)
include:
The application of the
HCM Chapter 15 procedure is considerably more complicated than the service
volume tables in HCM Chapter 10. Each signalized intersection must be
analyzed in detail using the signalized intersection analysis procedures
prescribed by HCM Chapter 16. Knowledge of the signal timing plan, as well
as the operating parameters for each approach, is required. Be sure to pay
special attention to the
percent-turns-from-exclusive-lanes parameter, which is frequently
overlooked or misunderstood. [
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] with Sub-Problem 3c |
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Sub-problem 3c: Operational
Analysis of the South Section of Krome Avenue (Class I Signalized Arterial
Facility)
What factors are used to determine urban
street LOS? The LOS for a
signalized arterial is based on the average speed over its entire length.
The average speed is computed by dividing the facility length by the total
travel time for each vehicle. The total travel time includes the
running time between signals and the
control delay for through
movements. The LOS thresholds
for a Class I arterial are shown in Exhibit 3-21.
Exhibit 3-21. LOS Thresholds
for Class I Arterials |
LOS A |
>42 mph |
LOS B |
>34-42 mph |
LOS C |
>27-34 mph |
LOS D |
>21-27 mph |
LOS E |
>16-21 mph |
LOS F |
<16 mph |
The running time is determined by an Exhibit within the HCM that provides a
running time based on the number of signals per unit length, the
free flow
speed, and the Class Type.
[
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Sub-problem 3c: Operational
Analysis of the South Section of Krome Avenue (Class I Signalized Arterial
Facility)
Step 2. Results.
Exhibit 3-22 compares the results from the planning level
analysis in
sub-problem 2c
with the operational level analysis. It shows the values
assumed by the service volume tables for all parameters, as compared with
the values that apply to this facility. It also shows the computations and
results for both methods. The overall average speed was 37.3 mph,
which suggests LOS B. This result is consistent with the planning
level analysis from
sub-problem 2c.
Exhibit 3-22. South Section: Comparison of
Planning and Operational Level Analysis Results |
|
Table Assumptions
HCM Chapter 10
Sub-problem 2c |
Field Observations
HCM Chapter 15
Sub-problem 3b |
Notes |
Classification |
I |
I |
Signal Density≈1 signal/mile |
Free Flow Speed |
50 mph |
50 mph |
Posted speed +5 mph |
Signal Density |
0.8 per mile |
1.0 per mile |
Scaled from map |
Cycle Length |
110 seconds |
88 seconds |
varies from 76 to 106 sec |
Effective g/c |
0.45 |
0.53 |
varies from 0.48 to 0.57 |
Adj. Sat. Flow Rate |
1,850 vphgpl |
1,744 vphgpl |
varies from 1,675 to 1,810 |
Arrival Type |
3 |
3 |
No coordination |
Unit Extension |
3 |
3 |
Average value |
Initial Queue |
0 |
0 |
None observed |
Other Delay |
0 |
0 |
None observed |
PHF |
0.92 |
0.92 |
None observed |
Turns from Exclusive Lanes |
10% |
11% |
Varies from 5% to 22% |
Left Turn Bays |
Yes |
Yes |
Except for Avocado |
Lane Utilization Factor |
1 |
1 |
|
Design Hour Volume |
812 |
812 |
Average value |
Chapter 10 Results |
LOS Thresholds |
|
LOS A |
--- |
>42 mph |
|
LOS B |
<860 vph |
>34-42 mph |
|
LOS C |
>860-930 vph |
>27-34 mph |
|
LOS D |
>930-1,020 vph |
>21-27 mph |
Travel Time=681 sec |
LOS E |
>1,020-1,140 vph |
>16-21 mph |
Section Length=7.08 miles |
LOS F |
>1,140 vph |
<16 mph |
Average Speed=37.4 mph |
LOS = B |
LOS = B |
[
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Sub-problem 3c: Operational
Analysis of the South Section of Krome Avenue (Class I Signalized Arterial
Facility)
To fully assess the operation of an arterial
route, each signalized intersection must be examined to ensure that it is
free of operating problems. The individual segment results are presented in
the table below. The volume to capacity (v/c) ratios are all well below
1.00, indicating that none of the approaches was oversaturated. The average
speeds are all within the 30-40 mph range, and the segment LOS values are
all within the B-C range.
Exhibit 3-23. Summary of
HCM Arterial Analysis Results (Northbound) |
|
Segment Length (mi) |
Travel Time (sec) |
Cycle Length (sec) |
g/c ratio |
v/c ratio |
Delay (sec) |
Average Speed (mph) |
LOS |
Biscayne Dr |
0.51 |
45 |
76 |
0.54 |
0.66 |
14 |
31.1 |
C |
Bauer Dr |
1.52 |
122 |
79 |
0.52 |
0.71 |
16 |
39.7 |
B |
Coconut Palm Dr |
1.01 |
81 |
81 |
0.57 |
0.58 |
12 |
39.3 |
B |
Silver Palm Dr |
1.02 |
82 |
91 |
0.56 |
0.64 |
15 |
38.1 |
B |
Hainlin Mill Dr |
1.01 |
81 |
81 |
0.57 |
0.63 |
13 |
38.8 |
B |
Quail Roost Dr |
1.00 |
80 |
81 |
0.57 |
0.61 |
12 |
38.9 |
B |
Eureka Dr |
1.01 |
81 |
106 |
0.48 |
0.81 |
28 |
33.4 |
C |
Exhibit 3-23 covers the peak direction on the arterial route. As an
additional check on the operation, each intersection should be examined to
determine whether or not any of the other movements experienced congestion.
A check of all movements indicated that two movements within this facility
were operating with oversaturated conditions:
|
Eastbound at Quail
Roost Drive: The single lane on this approach is not able to accommodate
the left, through, and right turning movements. The problem may be solved
easily by the addition of one lane to this approach. The HCM analysis is
very straightforward and does not merit further discussion as a separate
problem in this case study. |
|
Westbound
at Biscayne Drive: Again, the problem is caused by a single lane that
must accommodate all movements. In this case, there are some alternatives
that arise with respect to lane utilization. These alternatives will be
considered in Problem 6. |
Apart from these two trouble spots, the arterial operation is very simple. Most of the intersections are operating satisfactorily without
protected left turns on the cross street. There are much more complex
arterial facilities covered in other case studies in this guide. [
Back ] [
Continue ] to Problem 4 |
|