1. HCM 6th Edition: Signalized Intersections
Today’s web briefing is focused on the signalized intersections evaluation methods that are in Chapter 19 of the newly released HCM 6th Edition.

2. Instructor
[Note: Instructor should show their name, title, affiliation, and HCM-related background. If the presentation is via webinar, then add a photo of instructor]
My name is: _______________. I will be the instructor for today’s presentation. I am a _______________ with ____________.

3. Overview and Background
Session 1
Overview and Background
Briefing series overview
Objectives and scope of briefing
Note: “HCM” → Highway Capacity Manual
Content and Structure of HCM
Methodology Basics
New Capabilities
This briefing is organized into four sessions. The first session is intended to provide some context for our examination of the Signalized Intersections chapter. In this session, I plan to review the schedule for this briefing series and outline the objectives of this presentation.
The second session will identify the content and structure of the HCM 6th Edition, as it relates to the signalized intersections chapter. The third session will provide an overview of the methodologies in this chapter and highlight some of the new terms and concepts that are used. The last session will highlight some of the new evaluation capabilities of the methodologies.

4. Briefing Series Overview
What’s New – HCM 6th Edition
New Features in Freeway Analysis Chapter
Freeway Reliability and Strategy Assessment
Urban Street Segments
Urban Street Facilities
Signalized Intersections
Signalized Intersection Planning Application
Roundabouts
Ramp Terminals and Alternative Intersections
Planning and Preliminary Engineering Guide
Today’s briefing is being offered as one in a series of ten briefings on the HCM 6th Edition. This briefing on Signalized Intersections is the sixth in this series.

5. Objectives and Scope Learning Objectives Scope of Presentation Focus
Learn about new capabilities of the signalized intersection chapter
Understand how the chapter can be used to evaluate signalized intersection operation
Scope of Presentation
HCM 6th Edition
Signalized Intersections chapters
Focus
Changes since publication of HCM 2010
There are two objectives for today’s discussion. One objective is to help you learn about the new capabilities of the Signalized Intersection chapter. A second objective is to help you understand how the chapter can be used to evaluate signalized intersection operation.
Our discussion centers on the methodologies in the Signalized Intersections chapter of the HCM 6th Edition. These methodologies are used to evaluate intersection operation. There is one methodology for evaluating the motorized vehicle travel mode, one for evaluating the pedestrian mode, and one for the bicycle mode.
Given the limited time that we have for this presentation, we will need to focus our discussion on a few key topics. To this end, I am planning to focus on the changes made to the methodologies since their publication in HCM 2010.

6. Presentation Overview
Session 1 – Overview and Background
Session 2 – Content and Structure
Session 3 – Methodology Basics
Session 4 – New Capabilities
We are now ready to transition to Session 2. In this session, we will discuss the content and structure of the HCM 6th Edition, as it relates to signalized intersections.

7. Session 2 Content and Structure HCM organization Chapter titles
Chapter outlines
For this session, I will show you the organization of the HCM and describe how it will be changed for the soon-to-be-published HCM 6th Edition.
My approach will be to list the HCM chapters related to signalized intersections, describe the changes to the chapter titles, and summarize the changes being made to chapter contents.
Let’s get started...

8. Volume 2 – Uninterrupted Flow Volume 3 – Interrupted Flow
HCM Organization
Volume 1 - Concepts
Volume 2 – Uninterrupted Flow
Volume 3 – Interrupted Flow
Volume 4 – Applications Guide
The HCM consists of four volumes. They are shown here. No changes to volume titles will be made for the HCM 6th Edition.
The first three volumes are included in the printed copy of the manual. The fourth volume is available from the Internet at the address shown.
The chapters we will be discussing today are located in Volumes 3 and 4. Let’s take a closer look at them...

9. Chapters HCM 2010 HCM 6th Edition Volume 3 Volume 4 Volume 3 Volume 4
18: Signalized Intersections (SI)
Volume 4
31: SI Supplemental
HCM 6th Edition
Volume 3
19: Signalized Intersections
Volume 4
31: SI Supplemental
The signalized intersection information is currently located in Chapters 19 and 31. Chapter 19 is located in Volume 3, and Chapter 31 is located in Volume 4.
For the HCM 6th Edition, the chapter titles remain the same but the chapter number of one chapter will be increased from 18 to No change is made to the number of Chapter 31.
Ok, now let’s take a look at the section titles in each chapter...

10. Volume 3 Chapter Outline
HCM 2010
Chapter 18
Introduction
LOS criteria
Input data
Methodology
Auto methodology
Pedestrian method.
Bicycle methodology
Applications
Example Problems
HCM 6th Edition
Chapter 19
Introduction
Concepts
LOS criteria
Motorized Vehicle Method.
Input data
Pedestrian Methodology
Bicycle Methodology
Applications
All of the chapters in Volume 3 have been reorganized slightly for the HCM 6th Edition. Most notable is that each of the methodologies in a chapter will be assigned its own separate section in the HCM 6th Edition. This approach concentrates all of the information needed to apply a specific methodology into one section.
For signalized intersections, the new Chapter 19 will have three “methodology” sections. There is one section describing the methodology for evaluating the motorized vehicle travel mode, one section for the pedestrian mode, and one for the bicycle mode.
I should also note that the example problems have been moved from Chapter 18 to Chapter 31, which is in Volume 4.

11. Volume 4 Chapter Outline
HCM 2010
Chapter 31
Traffic Signal Concepts
Capacity & Phase Duration
Queue Accumulation Polygon
Queue Storage Ratio
Quick Estimation Method
Field Measurement Tech.
Computational Engine
Simulation Examples
Service Volume Tables
HCM 6th Edition
Chapter 31
Introduction
Capacity & Phase Duration
Queue Accumulation Polygon
Queue Storage Ratio
Planning-Level Analysis Application
Field Measurement Tech.
Computational Engine
Use of Alternative Tools
Example Problems
Chapter 31 is focused on the motorized vehicle travel mode and the motorized vehicle methodology in Chapter 19. Several of the initial sections in Chapter 31 describe supplemental procedures for the methodology.
For example, the first section describes the procedure for computing the capacity of each lane group and the duration of each signal phase.
The second section describes the procedure for computing the queue accumulation polygon. This polygon is used to define uniform delay for each lane group.
The third section describes a procedure for computing the queue length and queue storage ratio.
There is a section describing a simplified version of the methodology, as is often needed for planning-level analysis applications.
There is also a section describing a technique for measuring saturation flow rate and delay in the field.

12. Questions on Content or Structure?
Content and Structure
HCM organization
Chapter titles
Chapter outlines
Questions on Content or Structure?
This concludes the session on Content and Structure of the HCM. Let’s take a few minutes to answer some questions.

13. Presentation Overview
Session 1 – Overview and Background
Session 2 – Content and Structure
Session 3 – Methodology Basics
Session 4 – New Capabilities
OK, let’s continue with Session 3 - Methodology Basics

14. Session 3 Methodology Basics Calculation framework New input data
For this session, we will review the sequence of calculations represented by the methodology, and then we will discuss the new types of input data that are needed to use the methodology.

15. Calculation Framework
Motorized Vehicle Methodology
Ten steps
Determine movement groups and lane groups
Determine movement group flow rate
Determine lane group flow rate
Determine adjusted saturation flow rate
Determine proportion arriving during green
Determine signal phase duration (if actuated)
Determine capacity and v/c ratio
Determine delay
Determine LOS
Determine queue storage ratio
The methodology for evaluating motorized vehicle travel through a signalized intersection consists of ten calculation steps. They are completed in sequence for a complete evaluation. All ten steps are shown here. They are... [read]
I should note that the sequence of steps has not changed for the HCM 6th Edition.

16. Calculation Framework
Pedestrian Methodology
Five steps
Determine street corner circulation area
Average sidewalk area per pedestrian (ft2/p)
Determine crosswalk circulation area
Average crosswalk area per pedestrian (ft2/p)
Determine pedestrian delay
Delay when crossing street
Determine pedestrian LOS score
Determine LOS
The methodology for evaluating the service provided to pedestrians at a signalized intersection consists of five calculation steps. They are completed in sequence (from top to bottom) for a complete evaluation. All five steps are shown here. They are... [read]
The pedestrian LOS score for the intersection is computed in Step 4. It represents a number from 1 to 6, where a “1” indicates the best service. The equation used to predict this score was calibrated using data from surveys of pedestrians who were exposed to a range of intersection traffic and road conditions.
I should note that the sequence of steps has not changed for the HCM 6th Edition.

17. Calculation Framework
Bicycle Methodology
Three steps
Determine bicycle delay
Determine bicycle LOS score
Determine LOS
The methodology for evaluating the service provided to bicyclists at an intersection consists of three calculation steps. They are completed in sequence (from top to bottom) for a complete evaluation. All three steps are shown here. They are... [read]
The three steps are similar to the steps that comprise the pedestrian methodology. They include steps to guide the calculation of a bicyclist LOS score for the intersection.
I should note that the sequence of steps has not changed for the HCM 6th Edition.

18. Motorized Vehicle Methodology Pedestrian Methodology
New Input Data
Motorized Vehicle Methodology
Unsignalized movement volume and delay
Pedestrian Methodology
No new input data
Bicycle Methodology
Striped parking lane width
There were a few enhancements made to the methodologies for the HCM 6th Edition. Some of these enhancements led to the need for additional input data. These new input data are listed on this slide. They include... [read]
The use of the unsignalized movement volume and delay input data is discussed in a subsequent slide.

19. Questions on Methodology Basics?
Calculation framework
New input data
Questions on Methodology Basics?
This concludes the session on Methodology Basics. Let’s take a few minutes to answer some questions.

20. Presentation Overview
Session 1 – Overview and Background
Session 2 – Content and Structure
Session 3 – Methodology Basics
Session 4 – New Capabilities
OK, let’s continue with Session 4 - New Capabilities

21. Session 4 New Capabilities Motorized Vehicle Methodology
Unsignalized movements
Saturation flow rate adjustment factors
Intersection v/c ratio
Pedestrian and Bicycle Methodologies
Level of service
For this session, we will briefly look at the procedures that were added, or underwent major revision, for the HCM 6th Edition.
For the motorized vehicle methodology, the calculation of approach delay was modified to include the delay incurred by unsignalized movements at the intersection. There were also some changes to the saturation flow rate prediction procedure. Finally, the procedure for calculating intersection v/c ratio was revised to provide better explanation of the treatment of permitted left-turn operation.
For the pedestrian and bicycle methodologies, the level-of-service thresholds were adjusted slightly to make them consistent with the thresholds used when the models were originally calibrated. Apparently, the thresholds used in HCM 2010 were incorrectly reported.
We will take a look at all of these changes in the next few slides.

22. Motorized Vehicle Methodology
Unsignalized Movements
New guidance
Unsignalized movement delay should be included in...
Approach delay
Intersection delay
Analyst must report whether unsignalized delay is (or is not) included in results
The HCM 6th Edition advises that the delay to unsignalized movements at signalized intersections should be considered when computing aggregated delay estimates (such as the approach delay and the intersection delay). The guidance is general and applies to any type of unsignalized movement; however, it most frequently going to be applied to the right-turn movement from an uncontrolled free-right-turn lane (as shown for the southbound right turn in the plan view).
The HCM 6th Edition also advises that the reporting of all aggregated delay estimates must be annotated with a footnote indicating whether the delay of unsignalized movements is (or is not) included.
HCM Page and HCM Equations & 19-29

23. Motorized Vehicle Methodology
Unsignalized Movements
New guidance
No procedure in HCM for estimating unsignalized movement delay
Delay estimation options
Field Measurement
Observing Similar Conditions
Special HCM Application
Simulation
The HCM 6th Edition does not contain a procedure for estimating the delay to unsignalized movements. This may be the topic of future research.
The HCM 6th Edition does recommend that the delay for unsignalized movements should be provided whenever these movements exist. It also advises that the level of effort expended for such estimation should be commensurate with the relevance the unsignalized delay has to the overall analysis. For example, high-volume or high-delay movements should be estimated carefully. Free-flow right turns can be assumed to have zero delay. HCM Page 19-32

24. Motorized Vehicle Methodology
Saturation Flow Rate Adjustment Factor
Combined heavy vehicle and grade
HCM 2010 factors
HCM 6th Edition factor
Negative Grade Non-Negative Grade
Heavy Vehicles
Grade
The HCM 6th Edition provides a new saturation flow rate adjustment factor to better capture the combined influence of heavy vehicles and grade.
The HCM 2010 currently has one adjustment factor to quantify the effect of heavy vehicles on saturation flow rate, and one adjustment factor to quantify the effect of grade. These current factors are shown in the middle of the slide.
The HCM 6th Edition will combine the two adjustments for heavy vehicles and grade into one factor. There is one combined adjustment factor equation for negative grades, and one equation for non-negative grades. These equations are shown at the bottom of the slide.
HCM Equations 19-9 and 19-10

25. Motorized Vehicle Methodology
0% heavy vehicles
Sat. Flow Factor
10%
25%
50%
This figure compares the new and the old equations. The figure has grade along the x axis and the saturation flow rate adjustment factor on the y-axis.
The solid trend lines represent the product of the heavy vehicle factor and the grade factor from HCM Four lines are shown, depending on the percentage of heavy vehicles.
The dashed lines represent the combined factor that will be in the HCM 6th Edition. They show a steeper slope than the solid lines indicating that grade has a larger effect on saturation flow rate than indicated by the current factor. Similarly, the effect of heavy vehicles is a little larger than the current factor.
HCM 2010 – solid lines
HCM 6th Edition – dashed lines

26. Motorized Vehicle Methodology
Saturation Flow Rate Adjustment Factor
Work zone presence on intersection approach
with
The HCM 6th Edition will include a new new saturation flow adjustment factor for work zone presence. It is used to compute the saturation flow rate when when a work zone is present on an intersection approach.
The new factor is a function of two variables. One variable is total approach lane width. The other variable describes the difference between the number of open lanes during the work zone and during normal operations.
HCM Equations thru 31-91
aw = approach lane width when work zone present (total of all open lanes), ft
no = number of left-turn and through lanes open during normal operation
nwz = number of left-turn and through lanes open when work zone present

27. Motorized Vehicle Methodology
Saturation Flow Rate Adjustment Factor
Example values
Factor values in column 4
Resulting saturation flow rate in column 5 4 5
This slide provides some sample values to illustrate the effect of work zone presence.
For example, consider the first row of the table. It describes an intersection approach on which the total number of left-turn and through lanes is 2. Under normal conditions the saturation flow rate of these lanes averages 1,800 veh/h/ln.
However, when the work zone is present, one of the lanes is closed, leaving one open lane with a width of 11 feet. The saturation flow rate adjustment factor for this case is This results in a saturation flow rate of 1,476 (= 1800 x 0.820).
By scanning the remaining rows, you can see that the saturation flow rate is lowest when there are more lanes closed.

28. Motorized Vehicle Methodology
Intersection v/c Ratio
Procedure for calculating intersection v/c ratio clarified for...
Lane groups served by permitted-only or protected-permitted operation
Clarifications include...
New guidance for computing average sat. flow rate during permitted period
New guidance for apportioning volume to protected period and permitted periods of prot-perm operation
The procedure for calculating the intersection v/c ratio has been with the HCM for since However, when HCM 2010 was published, the guidance was not as clear as needed for cases where one or more lane groups was served by a permitted left-turn operation.
The procedure has been clarified HCM 6th Edition. The clarifications include... [read].
HCM Pages thru 19-62

29. Pedestrian and Bicycle Methodologies
Pedestrian and Bicycle LOS
LOS thresholds corrected
LOS
LOS Score
HCM 2010
HCM 6th Edition A
≤2.00
≤1.50 B
>2.00–2.75
>1.50–2.50 C
>2.75–3.50
>2.50–3.50 D
>3.50–4.25
>3.50–4.50 E
>4.25–5.00
>4.50–5.50 F
>5.00
>5.50
There was one change for the pedestrian methodology. Specifically, the level-of-service thresholds were adjusted slightly to make them consistent with the thresholds used when the models were originally calibrated. Apparently, the thresholds used in HCM 2010 were incorrectly reported.
The thresholds for the HCM 6th Edition are shown in the last column of the table. They can be contrasted with those in HCM 2010, which are shown in the second column.
The thresholds for service levels A and B (i.e., 1.5 and 2.5) have been reduced for the HCM 6th Edition. This change will result in some of the better performing links having a lower level of service. For example, a link having a score of 1.8 was reported as having LOS A using HCM Using the HCM 6th Edition thresholds, this link will have a LOS B.
In contrast, the thresholds for service levels D, E, and F have been increased for the HCM 6th Edition. This change will result in some of the poorer performing links having a higher level of service.

30. Software Availability
HCS7 – Streets (McTrans)
Combines...
Signalized intersections
Urban street segments
Urban street facilities
Ramp terminals and alternative intersections
Automatic...
Supported users can download upgrade
There are several software developers that have (or will) implement the new methodology in their software products. One of them, McTrans, is developing a software tool called “Streets”. It will ...[read]

31. Questions on New Capabilities?
Motorized Vehicle Methodology
Unsignalized movements
Saturation flow rate adjustment factors
Combined heavy vehicle and grade
Work zone presence
Intersection v/c ratio
Pedestrian and Bicycle Methodologies
Level of service
Questions on New Capabilities?
This concludes the session on New Capabilities. Let’s take a few minutes to answer some questions.

32. Forthcoming Briefings
Closure
Forthcoming Briefings
Just a reminder of the remaining briefings. There are ___ left. The topics are: [read]