cold as “ice” – intersection control evaluation using...

Cold as “ICE” – Intersection Control Evaluation Using HCM6

Thursday, November 14, 20192:00-3:30 PM ET

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Purpose

To discuss how the new and updated methods in the Highway Capacity Manual (HCM) and its companion, Planning & Preliminary Engineering Applications Guide (PPEAG), can be an integral part of the ICE process.

Learning Objectives

At the end of this webinar, you will be able to:

• Apply ICE methodologies

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Cold as “ICE”Intersection Control Evaluation using the Highway Capacity Manual, 6th

Edition

Welcome

2

§ Paul Ryus, Principal Engineer, Kittelson & Associates, Inc.

Instructors

3

§ Lee Rodegerdts, Principal Engineer, Kittelson & Associates, Inc.§ Matt Kittelson, Senior Engineer, Kittelson &

Associates, Inc.

Agenda

4

1. Introduction to Intersection Control Evaluation2. Applicable Content within HCM6 & Supplemental

Documents for ICE Evaluations3. Discussion of Two Key Methods4. Case Studies

Intersection Control Evaluations

5

§ National trends toward cost-effective solutions• “Right-sizing” project solutions• Considering the likely value versus simply addressing

projections• Performance-based Practical Design (PBPD)• Performance-based Analysis of Geometric Design

of Highways and Streets (NCHRP Report 785)

§ Increasing number of states and cities with roundabout policies• Roundabouts “first” or “also”

National Intersection Control Evaluation Trends

6

§ Supported by FHWA’sEvery Day Counts Initiative• Shortening project delivery• Enhancing roadway safety• Protecting the environment

§ FHWA has supported development on relevant guides• Roundabouts (2000, 2010,

ongoing)• Alternative Intersections

and Interchanges (2014, ongoing)

“DOTs should consider and evaluate [roundabouts, diverging diamond interchanges (DDIs) and intersections with displaced left-turns or variations on U-turns] early in the project scoping, planning and decision-making stages, as they may serve as more efficient, economical and safer solutions than traditional designs.”-FHWAhttp://www.fhwa.dot.gov/everydaycounts/edctwo/2012/geometrics.cfm

State Progress on ICE Policies (Source: Jeff Shaw, FHWA)

7

Intersection Control Evaluation General Steps

§ Consider project context

§ Initial screening evaluation

§ Performance-based decisions• Operations • Safety• Multimodal Quality of Service• Project Phasing • Life Cycle Cost

8

HCM6 or supplemental documents can help!

ICE: Common Considerations and Factors

§ Considerations• Footprint

• Traffic Operations

• Multimodal Quality of Service

• User Types

• Safety Performance

• Service Life

• Expandability

• Initial Capital Costs

• Benefit/Cost

9

Influencing factors§ Rural/Urban Context

§ High-Speed Environments

§ Intersection Forms

§ Corridors versus Isolated

§ Adjacent Traffic Control

§ Freight Movement

§ Special Vehicles

§ Pedestrian and Bicyclist

§ Demand

§ Special User Needs

Here, too!

Two Common Stages of ICE Evaluations

10

§ Stage 1: High-Level Screening of Alternatives• Limited design or operational detail available• Looking for sufficiency and fatal flaws• Tools:§ CAP-X§ HCM planning-level tools§ SPICE

Two Common Stages of ICE Evaluations (cont.)

11

§ Stage 2: More Detailed Assessment of Selected Alternatives• Calculation of performance metrics for operations, safety,

etc. to enable comprehensive comparison of alternatives• Tools:§ HCM preliminary engineering and operational-level assessments§ Simulation§ HSM predictive tools§ Life-Cycle Cost Evaluation Tool (NCHRP Project 03-110)

Agenda

12



Highway Capacity Manual 6th Edition

13

§ Four-volume structure as with HCM 2010§ Two most relevant sections for ICE evaluations:

• Volume 3, Interrupted Flow• Volume 4, Supplemental Material

§ Note: Some of the following slides are adapted from material Christopher Kinzel presented in the HCM 6th

Edition workshop at the 2017 TRB Annual Meeting

Volume 3: Interrupted Flow Chapters

16. Urban Street Facilities17. Urban Street Reliability and ATDM18. Urban Street Segments19. Signalized Intersections20. Two-Way Stop-Controlled

Intersections21. All-Way Stop-Controlled

Intersections22. Roundabouts23. Ramp Terminals and Alternative

Intersections24. Off-Street Pedestrian and Bicycle

Facilities

14

Printed Chapters

6th Edition201016. Urban Street Facilities

17. Urban Street Segments18. Signalized Intersections19. Two-Way Stop-Controlled

Intersections20. All-Way Stop-Controlled

Intersections21. Roundabouts22. Interchange Ramp Terminals

23. Off-Street Pedestrian and Bicycle Facilities

Reliability = Facility operations aggregated temporally

Volume 3: Hierarchical View

15

17

16 Facility = Segment operations aggregated spatially

Segment = Operations of link plus boundary intersection

18

Signalized AWSC Roundabouts ICRT & Alt Ints

TWSC

21 22 2319 20

24 Off-Street Pedestrian and Bicycle Facilities

HCM Multimodal Philosophy

Allow trade-offs in the use of the right-of-way by different modes to be evaluated

Mode Affected

Impacting Mode

Auto & HV volumesTurning patterns

Lane configurations

Minimum green timeTurn conflicts

Mid-block xings

Turn conflictsPassing delay

Heavy vehicleBlocking delay: stops

Signal priority

Auto & HV volumesSignal cycle length

Driver yieldingTurn conflicts

Traffic separation

Sidewalk crowdingCrosswalk crowding

Cross-flows

Shared-path conflictsBicyclist yielding

Heavy vehicleTransit stop queuesBus stop cross-flows

Vehicle yielding

Auto & HV volumesAuto & HV speedOn-street parking

Turn conflictsTraffic separation

Shared-path conflictsMin. green time

Turn conflictsMid-block xings

Bike volumesHeavy vehicle

Blocking delay: stopsTracks

Auto volumesSignal timing

Ped. env. qualityMinimum green time

Turn conflictsMid-block xings

Bike environment quality

Bike volumesBus volumes

16

Chapter 19 – Signalized Intersections

17

Provides methods to evaluate signalized intersection operations

Detailed control-delay-based LOS, or planning-level v/c ratio.

Ped LOS score based on cross-section, motorized vehicle volume & speed, and signal-based pedestrian delay. Corner and Circulation areas can also be computed and compared to standard ranges.

Bike LOS score based on cross-section, motorized vehicle volume. Signal-based bicycle delay can be also be computed and compared vs. general thresholds.

0% heavy vehicles10%25%

50%

Grade

Sat Flow Adj Factor HCM 2010

HCM 6th Ed

Chapter 19/31 Changes in 6th Edition (1/2)

18

§ Delay for unsignalized movements at signalized intersections• Now considered in approach and intersection delay

calculations§ Heavy vehicle &

grade adjustmentfor saturation flow• Now combined

in a single factor

Chapter 19/31 Changes in 6th Edition (2/2)

19

§ New saturation flow adjustment factors• Work zone presence at intersection• Midsegment lane blockage• Downstream segment with sustained spillback

§ Pedestrian / Bicycle LOS thresholds• Adjusted to more closely match original research

E

E

D

D

C

C

B

B

A

A

0 1 2 3 4 5 6

2010

6th Ed

F

F

Ped Bike LOS score

Chapter 20 – Two-Way Stop-Controlled Intersections

20

Provides methods to evaluate TWSC intersections based on gap-acceptance theory.

Motorized vehicle LOS based on control delay by movement– a function of priority ranking, critical headway, and follow-up headway. Intersection-wide control delay can also be computed.

Ped LOS based on delay, also a function of gap acceptance.

No bike method included; some qualitative guidance given.

Chapter 21 – All-Way Stop-Controlled Intersections

21

Provides methods to evaluate AWSC intersections using phase-based probabilities.

Motorized vehicle LOS based on control delay – a function of each possible conflict configuration and the probabilityassociated with that configuration.

Minimal, qualitative guidance.

Chapters 20/21/32 Changes in 6th Edition

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§ Methodologies unchanged from HCM 2010§ Peak hour factor guidance clarified

• Recommendation to use single peak-hour factor for entire intersection to avoid over-conservative calculations.

Chapter 22 – Roundabouts

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Provides methods to evaluate roundabouts using principally empirical regression methods with calibration anchors to driver behavior factors.

Motorized vehicle LOS based on control delay – a function of flow patterns, vehicle fleet mix, and lane configuration. Intersection-wide control delay can also be computed.

Minimal, qualitative guidance.

Chapter 23 – Ramp Terminals and Alternative Intersections

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§ Provides methods to evaluate interchange ramp terminals and some alternative intersections§ More detail to come in upcoming webinar

Supplemental Material

•25

§ Highway Capacity Manual Applications Guidebook§ Planning & Preliminary Engineering Applications

Guide

§ Both available in Volume 4:• www.hcmvolume4.org

HCM Applications Guidebook

§ The HCMAG presents six case studies demonstrating typical HCM applications to operations & design§ Focus is on selecting

appropriate methods, gathering data, and interpreting results

26

Planning and Preliminary Applications Guide

§ NCHRP Project 07-22 was funded to develop a planning counterpart to the HCMAG that would describe:• Appropriate use of the HCM to a broad

spectrum of planning applications• Use of default values and other HCM

tools• Use of the HCM in scenario planning• Coordinated use of HCM with planning

models• Use of the HCM in evaluating

oversaturated conditions in a planning context

27

28

Simplified HCM Method

§ Most HCM operations methods require specialized software to implement§ Using the HCM method with defaults may require

more resources than available or appropriate for the analysis§ The Guide presents simplified methods that are

HCM-compatible, but can be performed by hand or implemented in a basic spreadsheet§ This makes these simplified methods ideal for first-

stage ICE evaluations: the quick screening of alternatives

29

PPEAG Content Relevant for ICE

§ Medium-Level Analyses§ High-Level Analyses§ Working with Traffic

Demand Data§ Predicting Intersection

Traffic Control§ Default Values§ Service Volume Tables

§ Freeway Analyses§ Multilane Highways§ Two-Lane Highways§ Urban Streets§ Signalized Intersections§ STOP-Controlled

Intersections§ Roundabouts§ Pedestrians, Bicyclists,

and Public Transit§ Truck Level of Service

Agenda

30



HCM Analysis Methods for ICE Evaluations

31

§ Planning Methods from PPEAG:• Signalized Intersections• STOP-Controlled Intersections• Roundabouts

§ Operational Analysis Methods from HCM 6th Edition:• Signalized Intersections• Two-Way STOP-Controlled Intersections• All-Way STOP-Controlled Intersections• Roundabouts

Signalized Intersection Planning Method

32

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o: L

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s

Signalized Intersection Planning Method

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§ HCM 2010 Quick Estimation Method (QEM)• Requires calculation of delay to complete evaluation

§ New Planning-Level Analysis Application• Two-part procedure• First part produces estimate of “sufficiency”§ “Under”, “Near”, or “Over” capacity

• Second part produces delay estimate and LOS§ This part is used if delay and LOS are desired

Calculation Framework

34

§ Part I – Sufficiency Assessment• Five steps§ Determine left-turn operation

– Protected, permitted, split phasing, protected-permitted§ Convert movement volumes to through passenger-car equivalents

– Adjust for heavy vehicle presence, turning vehicles, parking, lane utilization, and other conditions

§ Assign flow rates to lane groups§ Determine critical lane groups

– Critical movement analysis§ Determine intersection sufficiency

– Under, near, or over capacity

Calculation Framework

35

§ Part II – Delay and LOS(steps continue from Part I)• Two steps§ Calculate capacity§ Determine delay and LOS

§ Worksheets to Document Results• Input worksheet• Left-turn treatment worksheet• Intersection sufficiency worksheet• Delay and LOS worksheet

Uses and Applications

36

§ Objective• To assess whether the intersection’s geometry is sufficient

to handle the volume§ Potential Uses

• Assess lane geometry sufficiency• Evaluate geometric alternatives • Estimate signal phasing and timing• Educate about the fundamentals of traffic signal

operational performance• Monitoring system performance

Limitations of Application

37

§ Does not consider performance of non-motorized-vehicle travel modes§ Does not account for effects of actuated control§ Does not analyze all phasing combinations§ Does not consider effect of poorly timed signals§ Does not account for upstream or downstream

impedances and effects of short lanes

Roundabout Operational Analysis Method

38

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Roundabout Methodology:Calculation Framework Unchanged from HCM 2010

39

Step 1: Convert movement demand volumes to flow rates

Step 2: Adjust flow rates for heavy vehicles

Step 5: Determine the capacity of each entry lane and bypass lane as appropriate in passenger car equivalents

Step 8: Compute the volume-to-capacity ratio for each lane

Step 9: Compute the average control delay for each lane

Step 10: Determine LOS for each lane on each approach

Step 11: Compute the average control delay and determine LOS for each approach and the roundabout as a whole

Step 12: Compute 95th percentile queues for each lane

Step 3: Determine circulating and exiting flow rates

Step 4: Determine entry flow rates by lane

Step 7: Convert lane flow rates and capacities into vehicles per hour

Step 6: Determine pedestrian impedance to vehicles

HCM 6th Ed., Exhibit 22-10

39

New Roundabout Capacity Equations

HCM 6th Ed., Exhibit 22-6

0

200

400

600

800

1,000

1,200

1,400

1,600

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200

Capa

city

(pc/

h)

Conflicting Flow Rate (pc/h)

Capacity of one-lane entry or right lane of two-lane entry against two conflicting lanes

Capacity of either lane of two-lane entry against one conflicting lane

Capacity of one entry lane against one conflicting lane

Capacity of left lane of two-lane entry against two conflicting lanes

3-4340

Roundabout Analysis Method

41

§ Modified Capacity Equations• New coefficients for existing equations• Calibrated to recently collected data• Predicted capacity tends to be higher

Entry Lanes

Opposing Lanes

Capacity by HCM Version and Conflicting Volume, veh/h

HCM 2010 HCM 6th Edition

Vc = 0 vph Vc = 1000 vph Vc = 0 vph Vc = 1000 vph

1 2 1130 561 1420 607

Right 2 1130 561 1420 607

Left 2 1130 534 1350 538

1 1 1130 416 1380 498

R or L 1 1130 416 1420 572

41

Calibration of Capacity

§ Procedure can be calibrated to local data to better capture local driver behavior

§ HCM 6th Edition is anchored to FHWA TOPR 34 data (most recent national study – data collected in 2012)

§ Form of empirical regression model allows for direct calibration to local field conditions• Calibrate intercept parameter using follow-up time (simpler), or• Calibrate intercept and slope parameters using follow-up time

and critical headway

5-42

Agenda

43



ICE Products

§ Many factors should be considered, for example:• Traffic operations • Safety performance • Footprint-practical and context sensitive• Design/Service Life, Life-cycle cost• Supporting or not precluding future projects• Etc.

§ Focus today is on one aspect of the larger effort

44

Operational Analysis Options

45

Software Options

46

§ Microsimulation§ Variety of HCM application software packages§ Planning & Preliminary Engineering Applications

Guide methods• Computational engines available

Highway Capacity Manual Volume 4

47

www.hcmvolume4.org

Applications Guides

48

Planning Tools Available

49

Case Study: US 95/Styner-Lauder

50

619198

38 435

61

201

478

72

1529867

Case Study Scope

51

§ Consider operational trade-offs of:• Unsignalized intersection• Signalized intersection• Roundabout

§ Additional steps possible:• Multiple lane configurations• Volume sensitivities • Etc.

52

Unsignalized Intersection: Input Parameters

§ Unsignalized:• Stop Control = EB/WB• Free Movement = NB/SB

§ Traffic Conditions:• Peak Hour Factor = 1.0• Heavy Vehicle Percentage = 2%

§ Planning Method Assumptions:• No pedestrians• No median on major street• No two-stage gap movements• No platooning from upstream

signals• No short right-turn lanes• No U-turns

§ Data Input:• Hourly volumes by

movement§ Methods exist for estimating

turning movements based on approach volumes

• Peak Hour Factor• Intersection Geometry

§ Lane configuration§ Stop-control

• % Heavy Vehicles• Critical & Follow-up

Headways (defaults)

Unsignalized Intersection Computational Engine

53

54

Unsignalized Intersection Results

Movement

ControlDelay v/c

Eastbound Left 220.7 0.99

Eastbound Thru/Right 56.6 0.78

Westbound Left 111.1 0.73

Westbound Thru/Right 82.6 0.94

55

Signalized Intersection: Input Parameters

§ Signalized Intersection:• Maintain lane configuration• Use default signal

configuration parameters

§ Traffic Conditions:• Peak Hour Factor = 1.0• Heavy Vehicle Percentage = 2%

Case Study: US 95/Styner-Lauder

56

619198

38 435

61

201

478

72

1529867

Signalized Intersection: Step 1

57

Signalized Intersection: Step 1 (cont.)

58

Signalized Intersection: Step 2

59

60

Roundabout: Input Parameters

§ Roundabout:• Single lane on each

approach• Single circulating lane

§ Traffic Conditions:• Peak Hour Factor = 1.0• Heavy Vehicle Percentage =

2%§ Planning Method

Assumptions:• No pedestrians• No bypass lanes• No more than two lanes

within the roundabout• No more than two lanes on

an approach

§ Data Input:• Hourly volumes by movement

§ Methods exist for estimating turning movements based on approach volumes

• Peak Hour Factor• Intersection Geometry

§ Number of lanes on approach§ Number of circulating lanes

• % Heavy Vehicles• Capacity values (HCM defaults)

Roundabout Volumes

61

Roundabout Computational Engine

62

Analysis Result Takeaways

63

§ Unsignalized intersection configuration is nearing capacity§ Signalized intersection and roundabout option are both viable§ Signalized intersection alternative may support a smaller

footprint

§ Additional considerations for ICE:• Potential right-of-way constraints• Safety trade-offs• Construction costs• Life-cycle costs• Environmental impacts• Economic impacts• Etc.

Upcoming HCM 6 Webinars

64

“Innovative Alternative Intersections and Corridor Planning using the HCM6”

§ December 5, 2019, 2:00pm-3:30pm ET

Questions?

65

§ Type your questions in the Questions pod located in the GoToWebinar control panel.

§ We will answer as many questions as possible before the webinar time ends.

Today’s Speakers

• From Kittelson & Associates:–Paul Ryus, [email protected]

–Lee Rodegerdts, [email protected]

–Matt Kittelson, [email protected]

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