Case Study 1Problem 3

Styner/Lauder IntersectionMoscow, Idaho

Problem 3Event Traffic Analysis - U.S. 95 Styner-Lauder Avenue Intersection

Using the HCM, what would be the LOS at U.S. 95/Styner-Lauder Avenue during a University of Idaho football game if the intersection were signalized?

How would this LOS estimate change if a microscopic simulation model were used instead?

What would the critical movement analysis technique tell us about the intersection’s sufficiency under these circumstances?

Questions to be answered:

Sub-problem 3a: Oversaturated Intersection Analysis

What is the difference between volume and demand, and why is it important to distinguish between these two terms?

Can the intersection operate at LOS F even when demand is less than capacity?

What is the appropriate value of the duration-of-analysis parameter when demand exceeds capacity? When should multiple time periods be considered in a capacity and level of service analysis?

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-27. U.S.95/Styner-Lauder Avenue Intersection Demand Volumes

Eastbound Westbound Northbound Southbound 15-min time period beginning LT TH RT LT TH RT LT TH RT LT TH RT

4:00 pm 40 55 175 50 50 75 100 815 45 40 700 55

4:15 pm 50 75 375 55 80 125 215 1,025 50 59 1,975 165

4:30 pm 30 75 125 45 75 115 20 975 35 55 1,200 145

4:45 pm 45 60 175 55 85 150 145 1,015 45 50 1,350 130

How will the intersection perform, under both signal control and stop sign control, for these demand conditions?

How should we proceed with this analysis?

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-28. Delay, Queue Length, and Level of Service at Styner-Lauder - Unsignalized Control (Dataset14)

Approach NB SB Westbound Eastbound

Lane configuration L L L TR L TR

v (vph) 215 59 55 205 50 450

c (vph) 256 656 0 3 0 6

v/c 0.84 0.09 68.33 75.00

95% queue length 6.8 0.3 28.0 58.4

Control delay 64.3 11.0

LOS F B F F F F

US

95

Lauder Styner

1025

1975

Step 2. Results

How will the intersection perform under signal control?

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-29. Lane Group Capacity, Control Delay, and LOS Determination at

Styner-Lauder - Signal Control (4:00-4:15 pm) (Dataset15)

Approach EB WB NB SB Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT Adj flow rate 40 230 50 125 100 860 40 755

Lane group capacity 322 421 246 432 405 2,089 330 2,083

v/c ratio 0.12 0.55 0.20 0.29 0.25 0.41 0.12 0.36

Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58

Control delay 18.2 24.6 19.6 19.9 7.5 7.5 4.2 4.5 Lane group LOS B C B B A A A A

Approach delay 23.6 19.8 7.5 4.5 Approach LOS C B A A Intersection delay 9.4 Intersection LOS A

US

95

Lauder Styner

Step 2. 1st period results: signal control

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-31. Excess Demand at Styner-Lauder under Signal Control (4:15-4:30 pm)

Approach EB WB NB SB

Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT

Adj flow rate 50 450 55 205 215 1,075 59 2,140

Lane group capacity 283 416 127 432 127 2,091 240 2,081

Excess demand (veh/hr) 34 88 59

Excess demand (vehicles) 9 22 15

Exhibit 1-30. Lane Group Capacity, Control Delay, and LOS Determination at

Styner-Lauder - Signal Control (4:15-4:30 pm) (Dataset16)

Approach EB WB NB SB

Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT

Adj flow rate 50 450 55 205 215 1,075 59 2,140

Lane group capacity 283 416 127 432 127 2,091 240 2,081

v/c ratio 0.18 1.08 0.43 0.47 1.69 0.51 0.25 1.03

Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58

Control delay 19.0 90.3 29.3 22.9 355.8 8.3 6.2 35.0

Lane group LOS B F C C F A A D

Approach delay 83.2 24.2 66.2 34.3

Approach LOS F C E C

Intersection delay 49.1 Intersection LOS D

Step 2. 2nd period results: signal control

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-33. Lane Group Capacity, Control Delay, and LOS Determination at

Styner-Lauder under Signal Control (4:30 - 4:45 pm) (Dataset17)

Approach EB WB NB SB

Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT

Adj flow rate 45 269 55 235 108 1060 50 1540

Lane group capacity 257 421 227 430 132 2092 246 2078

v/c ratio 0.18 0.64 0.24 0.55 0.82 0.51 0.20 0.74

Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58

Control delay 19.1 36.0 20.5 24.5 571.6 8.3 5.5 10.2

Lane group LOS B D C C F A A B

Approach delay 33.6 23.7 60.4 10.1

Approach LOS C C E B

Intersection delay 30.9 Intersection LOS C

Exhibit 1-32. Service Volumes vs. Demand Volumes at Styner-Lauder under Signal

Control (4:30 - 4:45 pm)

Eastbound Westbound Northbound Southbound Time Period LT TH RT LT TH RT LT TH RT LT TH RT

Initial demand (veh/hr), time period 3 45 60 175 55 85 150 20 1,015 45 50 1,350 130

Excess demand from time period 2 6 28 88 54 5

Final demand (veh/hr), time period 3 45 66 203 55 85 150 108 1,015 45 50 1,405 135

Step 2. 3rd period results: signal control

Sub-problem 3a: Oversaturated Intersection Analysis

Exhibit 1-33. Lane Group Capacity, Control Delay, and LOS Determination at

Styner-Lauder under Signal Control (4:30 - 4:45 pm) (Dataset17)

Approach EB WB NB SB

Movement LT TH/RT LT TH/RT LT TH/RT LT TH/RT

Adj flow rate 45 269 55 235 108 1060 50 1540

Lane group capacity 257 421 227 430 132 2092 246 2078

v/c ratio 0.18 0.64 0.24 0.55 0.82 0.51 0.20 0.74

Green ratio 0.25 0.25 0.25 0.25 0.58 0.58 0.58 0.58

Control delay 19.1 36.0 20.5 24.5 571.6 8.3 5.5 10.2

Lane group LOS B D C C F A A B

Approach delay 33.6 23.7 60.4 10.1

Approach LOS C C E B

Intersection delay 30.9 Intersection LOS C

Exhibit 1-32. Service Volumes vs. Demand Volumes at Styner-Lauder under Signal

Control (4:30 - 4:45 pm)

Eastbound Westbound Northbound Southbound Time Period LT TH RT LT TH RT LT TH RT LT TH RT

Initial demand (veh/hr), time period 3 45 60 175 55 85 150 20 1,015 45 50 1,350 130

Excess demand from time period 2 6 28 88 54 5

Final demand (veh/hr), time period 3 45 66 203 55 85 150 108 1,015 45 50 1,405 135

Step 2. 3rd period results: signal control

HCM chapter 34 provides information on simulation models

Microscopic simulation has several distinct attributes: Individual vehicle interactions Detailed operation of traffic

controllers Oversaturated conditions can

be directly modeled Multiple period inputs Probabilistic nature of traffic

flow and driver behavior More data are required Needs to be calibrated to

local conditions

Sub-Problem 3b: Using a Microscopic Simulation Model

Microscopic simulation models

Sub-Problem 3b: Using a Microscopic Simulation Model

Screen capture from a typical CORSIM animated display

What insights can we draw from a comparison of CORSIM and HCM results?

Problem 3c:Critical movement analysis

What is critical movement analysis? What data are needed? What outputs are produced? Are the results any more or less valid than the results

produced by the HCM or by microscopic simulation models?

Why is there virtually no difference between estimated delay on the eastbound and westbound approaches to the intersection?

What is the effect of grade and heavy vehicles? How do changes in vehicle mix affect the intersections

when the intersection operates near or at capacity? What effects do heavy vehicles have on the

intersection beyond changes to saturation flow rate?

Problem 3c:Critical movement analysis

Exhibit 1-36. Intersection Performance Assessment by Critical Volume Sum of Critical Volumes (v/hr) Intersection Performance Assessment

0-1,200 Under capacity 1,201 - 1,400 Near capacity

1,401 and above Over capacity

What is critical movement analysis? What data are needed to conduct critical movement analysis?

Critical movement analysis is a method to determine whether the projected volumes at a signalized intersection will be under, near, or over the intersection's capacity to accommodate them.

Data necessary to conduct a critical movement analysis include:

- Approach volume- Number of lanes- Lane configuration on each approach

Problem 3c:Critical movement analysis

Are the results from critical movement analysis any more or less valid than the results produced by the HCM or by microscopic simulation models?

Why is there virtually no difference between estimated delay on the eastbound and westbound approaches to the intersection?

What is the effect of grade and heavy vehicles? How do changes in vehicle mix affect the intersections

when the intersection operates near or at capacity? What effects do heavy vehicles have on the

intersection beyond changes to saturation flow rate?

Problem 3c:Critical movement analysis

Exhibit 1-37. Critical Movement Analysis at Styner-Lauder/U.S. 95

Intersection for peak event (Signal Control)

Conflicting Movements

Conflicting Volumes Conflicting Movements

Conflicting Volumes

EB LT volume 50 NB LT volume 215

WB TH/RT volume 205 SB TH/RT volume 1,070

Total conflicting volume 260 Total conflicting volume 1,285

WB LT volume 55 SB LT volume 59

EB TH/RT volume 450 NB TH/RT volume 522

Total conflicting volume 505 Total conflicting volume 581

Critical movement EW approaches

Conflicting

Volumes Critical movement

NS approaches

Conflicting

Volumes

WB LT

EB TH/RT 505

NB LT

SB TH/RT 1,285

Sum of critical movements 1,790

Assessment (under, near, above capacity) Above capacity

What is the primary result of critical movement analysis? What are the limitations of critical movement analysis?

Problem 3: Analysis

The ability of a traffic signal to handle fluctuations is a function of the signal timing that is in the controller in the field. In time period 3 (4:30 - 4:45 pm) of our previous analysis, we changed the green ratio slightly to serve the traffic at the post-game traffic at the intersection.

Would this green ratio be possible under the existing pre-timed control?

Problem 3: Discussion

Will the consideration of actuated traffic controller settings affect our analysis?

End of Problem 3