Case Study 1

Styner/Lauder IntersectionMoscow, Idaho

Problem: Should the intersection of U.S. 95 and Styner/Lauder be converted from two way stop control to signal control?

Learning skills: Apply HCM analysis procedures

for interrupted flow facilities. Know common input

requirements and default values.

Select an appropriate analysis procedure

Understand HCM analysis limitations

Know how to reasonably interpret the results

?

US 95

SH 8

Lauder Styner

Sweet

Overview

Moscow’s population is about 21,000

U.S. 95 is the primary north-south state highway in Idaho

ADT on U.S. 95 is between 15,000 and 23,000 vpd

Average annual traffic growth is about two percent per year

Introduction

Introduction

SH 8

US 95

Sweet

Lauder Styner

Introduction

SH 8

Sweet

Lauder

What issues do you think should be considered by the state's traffic engineer in resolving this problem?

Introduction

What issues do you think should be considered by the state's traffic engineer in resolving this problem?

City residents have asserted that increasing traffic volumes at the intersections of Styner Avenue, Lauder Avenue, and U.S. 95 are increasing delays for and reducing the safety of motorists traveling through the intersection.

The city has requested that the Idaho Transportation Department signalize the intersection.

Issues to consider

Scope of the analysis? Stakeholders? Goals? Performance measures? Tools? Data? Technical Issues?

Getting Started

Questions to be Answered:

What is the level of service at the existing TWSC intersection at U.S. 95/Styner-Lauder?

What would the level of service be if the intersection were signal controlled?

What would the level of service be at the intersection under future projected traffic conditions?

US

95

Lauder Styner

Problem 1U.S. 95/Styner-

Lauder Avenue

Sub-problem 1a. Analysis of the existing TWSC intersection

Sub-problem 1b. Analysis of the proposed signalized intersection

Sub-problem 1c. Analysis of future conditions

US

95

Lauder Styner

Problem 1U.S. 95/Styner-

Lauder Avenue

Analyses to be Undertaken:

Step 1. Setup: analysis of existing TWSC

Which tool or tools from the HCM should be used for the analysis of a TWSC intersection?

What data are required for the analysis?

What default values should be used?

What time periods should be analyzed?

What measure should be used to determine the performance of the intersection?

What other factors should be considered?

US

95

Lauder Styner

Sub-Problem 1aAnalysis of existing

TWSC intersection

US

95

Lauder Styner

Sub-Problem 1aAnalysis of existing

TWSC intersection

Exhibit 1-7. Existing traffic volumes, U.S. 95/Styner-Lauder Avenue

Approach LT (veh/hr) TH (veh/hr) RT (veh/hr) Eastbound 50 75 80 Westbound 55 80 125 Northbound 31 357 50 Southbound 59 392 165

Exhibit 1-8. Projected ten-year traffic volumes, U.S. 95/Styner-Lauder Avenue

Approach LT (veh/hr) TH (veh/hr) RT (veh/hr) Eastbound 61 91 98 Westbound 67 98 152 Northbound 38 435 61 Southbound 72 478 201

Sub-Problem 1aAnalysis of existing

TWSC intersection

Exhibit 1-9. U.S. 95/Styner Avenue-Lauder Avenue (Dataset1)

Delay, Queue Length, and Level of Service - Existing Volumes

Approach NB SB Westbound Eastbound

Movement 1 4 7 9 10 12

Lane configuration L L L TR L TR

v (vph) 31 59 55 205 50 155

c (vph) 1,024 1,163 170 359 134 329

v/c 0.03 0.05 0.32 0.57 0.37 0.47

95% queue length

(vehicles) 0.1 0.2 1.3 3.4 1.6 2.4

Control delay (sec/veh) 8.6 8.3 36.0 27.6 47.0 25.3

LOS A A E D E D

Approach delay

(sec/veh) -- -- 29.3 30.6

Approach LOS -- -- D D

Step 2. Results

Sub-Problem 1aAnalysis of existing

TWSC intersection

Exhibit 1-9. U.S. 95/Styner Avenue-Lauder Avenue (Dataset1)

Delay, Queue Length, and Level of Service - Existing Volumes

Approach NB SB Westbound Eastbound

Movement 1 4 7 9 10 12

Lane configuration L L L TR L TR

v (vph) 31 59 55 205 50 155

c (vph) 1,024 1,163 170 359 134 329

v/c 0.03 0.05 0.32 0.57 0.37 0.47

95% queue length

(vehicles) 0.1 0.2 1.3 3.4 1.6 2.4

Control delay (sec/veh) 8.6 8.3 36.0 27.6 47.0 25.3

LOS A A E D E D

Approach delay

(sec/veh) -- -- 29.3 30.6

Approach LOS -- -- D D

Step 2. Results (cont.)

Sub-Problem 1aAnalysis of existing

TWSC intersection

Intersection delay and LOS?

Exhibit 1-9. U.S. 95/Styner Avenue-Lauder Avenue (Dataset1)

Delay, Queue Length, and Level of Service - Existing Volumes

Approach NB SB Westbound Eastbound

Movement 1 4 7 9 10 12

Lane configuration L L L TR L TR

v (vph) 31 59 55 205 50 155

c (vph) 1,024 1,163 170 359 134 329

v/c 0.03 0.05 0.32 0.57 0.37 0.47

95% queue length

(vehicles) 0.1 0.2 1.3 3.4 1.6 2.4

Control delay (sec/veh) 8.6 8.3 36.0 27.6 47.0 25.3

LOS A A E D E D

Approach delay

(sec/veh) -- -- 29.3 30.6

Approach LOS -- -- D D

Step 2. Results (cont.)

Step 1. Setup: analysis of signal control

Which tool or tools should be used for this analysis?

What data are required for the analysis?

What default values should be used?

What time periods should be analyzed?

How do we construct a signal timing for a proposed traffic signal using the HCM?

US

95

Lauder Styner

Exhibit 1-10. Signal Timing Data for sub-problem 1b

Phase Movement Green Yellow All red 1 NB/SB 35 4 1

2 EB/WB 15 4 1

Sub-Problem 1bAnalysis of proposed

signalized intersection

Sub-Problem 1bAnalysis of proposed

signalized intersection

Exhibit 1-11. U.S. 95/Styner-Lauder Avenue (Dataset2)

Lane Group Capacity, Control Delay, and LOS Determination - Existing Volumes (Signal Control)

EB WB NB SB

LT TH/RT LT TH/RT LT TH/RT LT TH/RT Adjusted flow rate 50 155 55 205 31 407 59 557

Lane group capacity 276 438 313 432 491 2,067 569 2,012

v/c ratio 0.18 0.35 0.18 0.47 0.06 0.20 0.10 0.28

95% queue length 1.6 4.8 1.8 6.3 0.6 3.9 1.1 5.4

Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58

Control delay 19.0 20.7 18.9 22.9 5.7 6.1 5.9 6.6

Lane group LOS B C B C A A A A Approach delay 20.3 22.0 6.1 6.5

Approach LOS C C A A Intersection delay 10.9 Intersection LOS B

Critical v/c ratio 0.34

Step 2. Results

Step 1. Setup: analysis of future conditions

What is the appropriate future year for this analysis?

Which default values should be used for this future analysis?

What other factors should be considered?

US

95

Lauder Styner

Sub-Problem 1cAnalysis of future

conditions

Sub-Problem 1cAnalysis of future

conditions

Exhibit 1-12. U.S. 95/Styner-Lauder Avenue (Dataset3)

Delay, Queue Length, and Level of Service - Projected Ten Year Volumes (Unsignalized control)

Approach NB SB Westbound Eastbound

Lane configuration L L L TR L TR

v (vph) 38 72 67 250 61 189

c (vph) 923 1,078 84 267 53 246

v/c 0.04 0.07 0.80 0.94 1.15 0.77

95% queue length 0.13 0.21 4.06 8.68 5.31 5.58

Control delay 9.1 8.6 134.4 80.9 297.5 55.7

LOS A A F F F F

Approach delay -- -- 92.2 114.7

Approach LOS -- -- F F

TodayFuture

27.680.9

115

Step 2. Results for TWSC control

Sub-Problem 1cAnalysis of future

conditions

Exhibit 1-13. U.S. 95/Styner-Lauder Avenue (Dataset4)

Lane Group Capacity, Control Delay, and LOS Determination - Ten Year Volume Forecast (Signal

control)

Approach EB WB NB SB Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT Adj flow rate 61 189 67 250 38 496 72 679 Lane group capacity 222 438 295 432 421 2,067 521 2,012 v/c ratio 0.27 0.43 0.23 0.58 0.09 0.24 0.14 0.34 95% queue length 2.0 5.8 2.2 7.6 0.7 4.8 1.4 6.6 Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58 Control delay 21.2 22.0 19.7 25.3 5.9 6.3 6.2 6.9 Lane group LOS C C B C A A A A Approach delay 21.6 24.1 6.3 6.9 Approach LOS C C A A Intersection delay 11.6 Intersection LOS B Crtical v/c ratio 0.34

Step 2. Results for signal control

Sub-Problem 1cAnalysis of future

conditions

What if our volume assumptions are uncertain?

Sub-Problem 1cAnalysis of future

conditions

Graphical presentation of results

Sub-Problem 1cAnalysis of future

conditions

Graphical presentation of results

Problem 1

Analysis

Exhibit 1-19. Summary comparison of average control delay estimates

(sec/veh)

Existing volumes Future volumes Movement

TWSC Signal control TWSC Signal control

EB LT 47.0 19.1 297.5 21.2

EB TH/RT 25.3 20.7 55.7 22.0

WB LT 36.0 18.9 134.4 19.7

WB TH/RT 27.6 22.9 80.9 25.3

NB LT 8.6 5.7 9.1 5.9

NB TH/RT 6.1 6.3

SB LT 8.3 5.9 8.6 6.2

SB TH/RT 6.6 6.9

Problem 1

Discussion

End of Problem 1