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NCHRP 15-34A Performance-Based Analysis of Geometric Design of Highways and Streets Kittelson & Associates, Inc. University of Utah January 2014 1.

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Presentation on theme: "NCHRP 15-34A Performance-Based Analysis of Geometric Design of Highways and Streets Kittelson & Associates, Inc. University of Utah January 2014 1."— Presentation transcript:

1 NCHRP 15-34A Performance-Based Analysis of Geometric Design of Highways and Streets Kittelson & Associates, Inc. University of Utah January

2 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 2

3 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 3

4 Project Background and Overview Past NCHRP Transition to NCHRP 15-34A Project Team Project Goals 4

5 Project Background – NCHRP Past NCHRP – The original intent of NCHRP project was to facilitate the transference of research findings and performance-prediction technologies to application within highway and street decision- making processes. Transition to NCHRP 15-34A – January 2007 Interim Report 1 – February 2007 Project Panel Meeting – Fall 2007 Principal Investigator Change – 2008/2009 Conduct Work – June 2009 Project Panel Meeting – March 2010 Project Stopped – Late Summer 2012 Project NCHRP 15-34A Initiated 5

6 Project Overview – NCHRP 15-34A Project Team – Kittelson & Associates, Inc. – Brian Ray and Erin Ferguson – University of Utah – RJ Porter – Dr. John Mason Project Goals – Review past material developed under NCHRP – Develop NCHRP Report 15-34A – Summarize research finding in the Supplemental Research Materials Report Archived material, additional research details, AASHTO Green Book revisions, and future suggested research 6

7 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 7

8 Information Gathering Key Materials Obtained from NCHRP – Original proposal – Original work plan – Phase I working files – First Interim Report – Framework Construction – Update on project activities – Draft of Second Interim Report – Kwon Final Thesis – Presentation files from TRB workshops – Panel comments to proposal and both interim reports – Panel Meeting notes from two panel meetings 8

9 Information Gathering Material to be archived – Information primarily from NCHRP First Interim Report (January 2007) definitions and timing of design decisions recommended performance measures capabilities of performance prediction tools sensitivity of performance measures to geometric design decisions NCHRP archived material is located: https://sites.google.com/site/nchrp1534archive/ 9

10 Information Gathering Material used NCHRP Report 15-34A – Similar project development process environmental clearance activities – Tables and matrix summaries of design elements, design decisions, and resources/software/tools available evaluate the performance effects of design decisions – Updated performance categories consistent with broader, national performance-based transportation decision making efforts – Specific recommended performance measures capture panel priorities more recent completed research 10

11 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 11

12 Project Work Plan – Develop NCHRP Report 15-34A Deliverables – Annotated Outline of the NCHRP Report 15-34A – Draft Report documents – Final Report documents NCHRP Report 15-34A Supplemental Research Materials Report Key Components – Coordinate with the panel to receive input – Consider past information gathered – Incorporate new research material available 12

13 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 13

14 NCHRP 15-34A Report Part A: Basis and Knowledge for Performance Based Analysis in Geometric Design of Highways and Streets – Chapter 1 through 4 Overview Part B: Applications Guidance for Conducting Performance Based Analysis – Chapter 5 - Framework – Chapter 6 - Project Examples 14

15 NCHRP 15-34A Report Part A – Chapter 1 – Introduction – Chapter 2 – Overview – Chapter 3 – Identify Project Outcomes – Chapter 4 – Geometric Design Elements Part B – Chapter 5 – Process Framework – Chapter 6 – Case Studies/Project Examples 15

16 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 16

17 Chapter 1 - Introduction Role of performance-based analysis in transportation activities Role and value in geometric design of highways and streets Guiding Principles – Intended outcomes – Connect to project development process – Performance measures of design decisions 17

18 Chapter 1 - Introduction Fundamental model of the approach 18

19 Chapter 1 - Introduction Performance-based analysis of geometric design – principles-focused approach that looks at the outcomes of design decisions as the primary measure of design effectiveness. Identifying project intended outcomes – basis for evaluating performance Geometric design performance – Influences whether a project achieves intended outcomes 19

20 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 20

21 Chapter 2 – Overview Overview of geometric design decisions 21

22 Chapter 2 – Overview Relationship between project-level and performance measures 22

23 Chapter 2 - Overview Geometric design and the project development stages – Planning Studies – not included – Alternatives Identification and Evaluation Project initiation, purpose and need, traffic analyses, preliminary alternatives, public outreach, technical studies, cost/benefit evaluations, refined analyses, selected alternative(s). 23

24 Chapter 2 - Overview Geometric design and the project development stages - continued – Preliminary Design Horizontal and vertical alignment, typical sections, grading plans, structures, traffic/ITS, signing and striping, illumination, and utilities. – Final Design – Construction 24

25 Chapter 2 – Overview Geometric design and environmental evaluations and clearance – Project Scoping – Purpose and Need – Alternatives Analysis – Effected Environment – Environmental Consequences – Mitigation 25

26 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 26

27 Chapter 3 – Identify Project Outcomes Fundamentally: Who are we serving? – Who are we serving? identifying the key road users and stakeholders for a given project and project context – What are we trying to achieve? identifying and articulating the core desired outcomes from the project 27

28 Defining Project Performance – Goals and Measures Chapter 3 – Identify Project Outcomes – US DOT’s Strategic Plan for Economic competitiveness Environmental sustainability Livable communities Organizational excellence Safety State of good repair 28 – Moving Ahead for Progress in the 21st Century Act (MAP- 21) Congestion Reduction Infrastructure Condition Environmental Sustainability Freight Movement and Economic Vitality Reduced Project Delivery Delays Safety System Reliability

29 Chapter 3 – Identify Project Outcomes Geometric Design Performance Categories – Accessibility ability to approach a desired destination or potential opportunity for activity using highways and streets (including the sidewalks and/or bicycle lanes). – Mobility ability to move various users efficiently from one place to another using highways and streets. – Quality of Service the perceived quality of travel by a road user. – Reliability consistency of performance over a series of time periods. – Safety expected frequency and severity of crashes occurring on highways and streets. 29

30 Chapter 3 – Identify Project Outcomes Role and Influence of Geometric Design Features 30 Performance Category Defined Role/Influence of Geometric Design Features Well Documented Moderate Documentation Limited Documentation Accessibility X Mobility X Reliability X Safety X Quality of Service X

31 Chapter 3 – Identify Project Outcomes Geometric Design Decisions – consider overall intended project outcomes, project performance, and transportation performance. How do the features or qualities of the features influence performance measures related to accessibility, mobility, quality of service, reliability, and safety? – may have incremental and cumulative effects – discrete choices may impact broader concepts sustainability, economic competitiveness, or livability – identifying project design controls leads to appropriate design criteria to meet those design control needs 31

32 Chapter 3 – Identify Project Outcomes Project Design Controls and Influences – Speed concepts and design decisions – Sight distance concepts – Design choices for segments and nodes 32

33 Chapter 3 – Identify Project Outcomes Design choices for segments 33 Example Design Decisions for Segments  Access points and density  Design speed and target speed  Horizontal alignment  Number of travel lanes  Sidewalk and pedestrian facilities  Bicycle accommodation features  Transit accommodation features  Design vehicle accommodation  Median provisions  Travel lane widths  Auxiliary lane widths  Type and location of auxiliary lanes  Shoulder width  Shoulder type  Lane and shoulder cross slopes  Superelevation  Roadside design features  Roadside barrier  Minimum horizontal clearance  Minimum sight distance  Maximum grade  Minimum vertical clearance  Vertical alignment  Bridge cross section  Bridge length/termini  Rumble strips

34 Chapter 3 – Identify Project Outcomes Design choices for nodes 34 Example Design Decisions for Nodes - Intersections and Interchanges  Intersection form, control type, and features  Interchange form and features  Design speed and target speed  Number and types of lanes  Sidewalk and pedestrian facilities  Bicycle accommodations facilities  Transit accommodations facilities  Special/vulnerable user treatments  Design vehicle accommodations  Traffic islands  Lane widths  Auxiliary lane lengths  Shoulder width and composition  Approach or ramp cross section  Horizontal alignment of approaches or ramp  Mainline ramp gores and terminals  Cross road ramp terminals  Vertical alignment of approaches or ramp  Auxiliary lane terminals and transitions  Pavement cross slope and superelevation  Intersection sight distance  Median opening configuration  Curve tapers & radii  Ramp roadside  Ramp barriers

35 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 35

36 Chapter 4 – Geometric Design Elements Introduction – Summarize critical or high priority known relationships between design elements and performance – Document the general relationship – Identify possibly performance trade-offs – Present resources and tools that can be used 36

37 Chapter 4 – Geometric Design Elements Overview – Key Resources AASHTO’s Highway Safety Manual (HSM) 2010 Highway Capacity Manual (2010 HCM) Transit Capacity and Quality of Service Manual, 2 nd Edition (TCQSM) FHWA’s Speed Concepts: Informational Guide Draft 2010 HSM chapters for freeways and interchanges (NCHRP Project 17-45) Interactive Highway Safety Design Model (IHSDM) 37

38 Chapter 4 – Geometric Design Elements Overview - Notations – Each characteristic/decision – performance measure category combination is classified as: Expected direct effect Expected indirect effect No expected effect 38

39 Chapter 4 – Geometric Design Elements Overview - Notations – Secondary notation classifies each relationship as one of the following : The relationship can be directly estimated by existing performance prediction tools; The relationship can be indirectly estimated using more than one existing tool or supplemental calculations; The relationship cannot be estimated by existing tools; or Not applicable (i.e., the relationship does not exist). 39

40 Chapter 4 – Geometric Design Elements Expected relationships between geometric design elements and performance categories – Segments – Nodes – Intersections and Interchanges 40 ● = expected direct effect □ = expected indirect effect -- = expected not to have an effect * = relationship can be directly estimated by existing performance prediction tools ◊ = relationship can be indirectly estimated using more than one existing tool x = relationship cannot be estimated by existing tools

41 Chapter 4 – Geometric Design Elements Segments 41 Segment Geometric Elements/CharacteristicsAccessibilityMobilityQuality of ServiceReliabilitySafety Access points and density●*●* ●*●* ●*●* □◊□◊ ●*●* Design speed and target speed--□◊□◊ □◊□◊ □◊□◊ □*□* Horizontal alignment--●◊●◊ ●◊●◊ □◊□◊ ●*●* Number of travel lanes●*●* ●*●* ●*●* □*□* ●*●* Sidewalk and pedestrian facilities●●*●* ●*●* □x□x ●x●x Bicycle accommodation features●●*●* ●*●* □x□x ●x●x Median provisions●◊●◊ ●*●* ●*●* □◊□◊ ●*●* Travel lane width(s)●◊●◊ ●*●* ●*●* □*□* ●*●* Auxiliary lane width(s)●x●x ●x●x ●x●x □x□x ●x●x Type and location of auxiliary lanes●◊●◊ ●*●* ●*●* □◊□◊ ●*●* Shoulder width(s) and composition●◊●◊ ●*●* ●*●* □*□* ●*●* Shoulder type(s)●◊●◊ ●x●x ●x●x □◊□◊ ●*●* Lane & shoulder cross slopes-- □x□x ●x●x Superelevation--●x●x ●x●x □◊□◊ ●*●* Roadside design features●x●x ●x●x ●x●x □x□x ●*●* Roadside barriers●◊●◊ ●*●* ●*●* □◊□◊ ●*●* Minimum horizontal clearances●◊●◊ ●*●* ●*●* □◊□◊ ●*●* Minimum sight distance●x●x ●x●x ●x●x □x□x ●x●x Maximum grade(s)□◊□◊ □*□* □*□* □◊□◊ □*□* Minimum vertical clearances●◊●◊ □x□x □x□x □x□x □x□x Vertical alignment(s)--●*●* ●*●* □*□* ●*●* Bridge cross section●◊●◊ ●*●* ●*●* □*□* ●*●* Bridge length/ termini-- □◊□◊ ●*●* Rumble strips●◊●◊ -- □x□x ●*●*

42 Chapter 4 – Geometric Design Elements Nodes – Intersections 42 Intersection Geometric Elements/CharacteristicsAccessibilityMobility Quality of ServiceReliabilitySafety Intersection form, control type, and features ●◊●◊ ●*●* ●*●* □x□x ●*●* Number and types of lanes ●◊●◊ ●*●* ●*●* □x□x ●*●* Sidewalk and pedestrian facilities ●*●* ●*●* ●*●* □x□x ●x●x Bicycle accommodation facilities ●*●* ●*●* ●*●* □x□x ●x●x Design vehicle accommodations □x□x □x□x □x□x □x□x □x□x Traffic islands ●x●x ●x●x ●x●x □x□x ●x●x Lane widths ●x●x ●x●x ●x●x □x□x ●x●x Auxiliary lane terminals and transitions ●◊●◊ ●*●* ●*●* □x□x ●x●x Shoulder width and composition ●x●x ●x●x ●x●x □x□x ●x●x Horizontal alignment of approaches ●x●x ●x●x ●x●x □x□x ●*●* Vertical alignment of approaches ●◊●◊ ●*●* ●*●* □x□x ●*●* Pavement cross slope and superelevation -- □x□x ●x●x Intersection sight distance ●x●x ●x●x ●x●x □x□x ●x●x Median opening configuration ●◊●◊ ●◊●◊ ●◊●◊ □x□x ●x●x Curve tapers and radii ●x●x ●x●x ●x●x □x□x ●x●x

43 Chapter 4 – Geometric Design Elements Nodes – Interchanges 43 Interchange Geometric Elements/CharacteristicsAccessibilityMobility Quality of Service ReliabilitySafety Interchange form and features ●◊●◊ ●◊●◊ ●x●x □x□x ●*●* Sidewalk and pedestrian facilities ●x●x ●x●x ●x●x □x□x ●x●x Bicycle accommodation facilities ●x●x ●x●x ●x●x □x□x ●x●x Auxiliary lane lengths ●◊●◊ ●*●* ●*●* □x□x ●*●* Horizontal alignment of ramp ●◊●◊ ●◊●◊ ●x●x □x□x ●*●* Vertical alignment or ramp ●x●x ●x●x ●x●x □x□x ●x●x Pavement cross slope and superelevation ●x●x ●x●x -- □x□x ●x●x Ramp cross section ●◊●◊ ●*●* ●*●* □x□x ●*●* Mainline ramp gores and terminals ●◊●◊ ●*●* ●*●* □x□x ●*●* Ramp roadside ●x●x ●x●x -- □x□x ●x●x Ramp barriers ●x●x ●x●x ●x●x □x□x ●*●* Cross road ramp terminals ●◊●◊ ●*●* ●*●* □x□x ●*●*

44 Chapter 4 – Geometric Design Elements Geometric Design Decisions and Performance – Accessibility ability to approach a desired destination or potential opportunity for activity using highways and streets (including the sidewalks and/or bicycle lanes). – Mobility ability to move various users efficiently from one place to another using highways and streets. – Quality of Service the perceived quality of travel by a road user. – Reliability consistency of performance over a series of time periods. – Safety expected frequency and severity of crashes occurring on highways and streets. 44

45 Chapter 4 – Geometric Design Elements Tables summarize the design elements/decisions and their relationship to performance measures from each of the transportation performance categories Key Resources AASHTO’s Highway Safety Manual (HSM) 2010 Highway Capacity Manual (2010 HCM) Transit Capacity and Quality of Service Manual, 2 nd Edition (TCQSM) FHWA’s Speed Concepts: Informational Guide Draft 2010 HSM chapters for freeways and interchanges (NCHRP Project 17-45) Interactive Highway Safety Design Model (IHSDM) NCHRP Report 687, Guidelines for Ramp and Interchange Spacing NCHRP 672, Roundabouts: An Informational Guide, 2 nd Edition 45

46 Chapter 4 – Geometric Design Elements Accessibility 46 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs SegmentDriveway Density Number of driveways per mile Access points and density Higher density of driveways associated with higher motor vehicle access Degrade bicycle LOS, Increase crash likelihood, Increase average travel speed Urban/ Suburban Segment Transit stop spacing Distance between transit stops along a roadway segment Transit accommodation features Higher frequency increases access for transit riders Increases transit travel time and may degrade mobility for other vehicle modes Segment Presence of Pedestrian Facility Presence of a sidewalk, multiuse path or shoulder Sidewalk and pedestrian facilities Greater connectivity and continuity of pedestrian network increases access for pedestrians Implementing pedestrian facilities in a constrained environment may require removing capacity or parking for vehicle mode Segment Presence of Bicycle Facility Presence of bicycle lanes, multiuse path, or shoulder Bicycle accommodation features Greater connectivity and continuity of bicycle network increases access for bicyclists Implementing bicycle facilities in a constrained environment may require removing capacity or parking for vehicle mode

47 Chapter 4 – Geometric Design Elements Mobility 47 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs Segment Average Travel Time The mean amount of time it takes a roader user to travel from one point to another point along a roadway segment. Number of travel lanes Increased vehicle lanes decrease average travel time for autos and increases vehicle speed. Degrades quality of service for pedestrians and bicyclists. Degrade mobility for pedestrians and bicyclists. Higher vehicle speeds are associated with higher severity crashes. SegmentInferred speed The maximum speed for which all critical design- speed-related criteria are met at a particular location. Horizontal alignment, vertical alignment, and cross- section Higher inferred speeds associated with higher free flow speeds and higher mobility. Higher vehicle speeds are also associated with higher severity crashes. Two-Lane Segment Average percent time spent following The average percent of total travel time that vehicles must travel in platoons behind slower vehicles due to an inability to pass. Horizontal and vertical alignment, sight distance, Type and location of auxiliary lanes Increased opportunities to pass slow moving vehicles reduces percent time spent following, providing a passing lane can reduce crashes. Increase vehicle speeds, increase potential for higher severity crashes.

48 Chapter 4 – Geometric Design Elements Mobility 48 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs Freeway Segment Freeway Speed The freeway speed down stream of an entrance ramp and before an exit ramp or another entrance ramp Ramp spacing dimensions as defined in NCHRP Report 687. Use of downstream auxiliary lane At relatively high exit ramp volumes, ramp spacing affects freeway speeds Decreased freeway speeds are possible with decreased ramp spacing. An auxiliary lane may improve freeway speeds Intersection Delay Average control delay experienced by road users at an intersection. Intersection form, control type, and features, Number and types of lanes Lower control delay for any road user improves mobility for that mode Often tradeoffs between delay experienced by different modes depending on the type of traffic control present. Volume to Capacity (v/c) Ratio The ratio of volume present or forecasted and the available capacity at the intersection. Intersection form, control type, and features, Number and types of lanes Increased vehicle capacity associated with lower v/c ratios. Degrades quality of service for pedestrians and bicyclists. Degrade mobility for pedestrians and bicyclists.

49 Chapter 4 – Geometric Design Elements Quality of Service 49 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs Urban/ Suburban Segment Pedestrian LOS A letter grade associated with the quality of travel experience for a pedestrian. Based on HCM 2010 methodology. Sidewalk and pedestrian facilities, width of pedestrian lanes, buffer from vehicle traffic, driveway density, crossing frequency Increasing width of pedestrian facility, increasing distance from vehicle traffic, decreasing driveway density, and increasing opportunities to cross a street improves pedestrian LOS Meeting performance metrics for pedestrians may degrade travel quality for other modes – e.g., on-street parking improves pedestrian LOS and degrades bicycle LOS Urban/ Suburban Intersections Pedestrian LOS A letter grade associated with the quality of travel experience for a pedestrian. Based on HCM 2010 methodology. Crossing distance, traffic control delay Decreasing pedestrian crossing distance and delay to cross a street improves pedestrian LOS Meeting performance metrics for pedestrians may degrade travel quality for other modes

50 Chapter 4 – Geometric Design Elements Quality of Service 50 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs Urban/ Suburban Segment Bicycle LOS A letter grade associated with the quality of travel experience for a bicyclist. Based on HCM 2010 methodology. Bicycle accommodation features, physical separation from motor vehicle traffic, access points and density, on street parking Increasing width of bicycle facility, decreasing driveway density, increasing separation from moving vehicle traffic, and removing on-street parking improves bicycle LOS Meeting performance metrics for bicyclists may degrade travel quality for other modes Urban/ Suburban Intersections Bicycle LOS A letter grade associated with the quality of travel experience for a bicyclist. Based on HCM 2010 methodology. Traffic control delay Decreased delay for bicyclists increases quality of travel experience Meeting performance metrics for bicyclists may degrade travel quality for other modes

51 Chapter 4 – Geometric Design Elements Quality of Service 51 Facility Type Performance MeasureDefinition Geometric Design ElementsBasic Relationship Potential Performance Tradeoffs Urban/ Suburban Segments and Intersections Transit LOS A letter grade associated with the quality of travel experience for a transit rider. Based on HCM 2010 methodology. Transit accommodations facilities (presence of transit only lane, bus pull out areas, bus merge/diverge lanes, bus queue jump lanes) Providing bus only lane, queue jump lanes, merge/diverge lanes decreases bus travel time and improves transit rider quality of travel Incorporating transit only features often comes at the expense of providing additional auto or bicycle capacity or treatments Urban/ Suburban Segments and Intersections Auto LOS Number and duration of stops along an urban/suburban corridor. Number of travel lanes, intersection form, control type, and features Reducing the number of stops and duration of stops along a corridor improves auto MMLOS Increased vehicle lanes and speeds degrades pedestrian and bicycle MMLOS Intersections and Segments Large Vehicle Turning and Off- Tracking Characteristics Ability and ease with which large vehicles are able to physically move through an intersection or along a segment Curve radii, curb radii, lane width Generally larger curve radii, larger curb radii and wider vehicle lanes enable easier navigation for larger vehicles Increasing curve radii, curb radii, and lane width often degrade pedestrian and bicycle MMLOS due to the longer crossing distances

52 Chapter 4 – Geometric Design Elements Reliability 52 On-going research to develop performance measures to connect reliability to specific geometric design elements Variation in travel time and variation in speed are two more common performance measures There are no clear performance measures available to easily integrate into design decision Additional reliability resources: – SHRP 2 L07: Evaluation of Cost-Effectiveness of Highway Design Features (9) – SHRP 2 L08: Incorporation of Travel Time Reliability into the Highway Capacity Manual (10) – SHRP 2 L09: Incorporation of Non-recurrent Congestion Factors into the AASHTO Policy on Geometric Design (11)

53 Chapter 4 – Geometric Design Elements Reliability 53 There are a number of design considerations that can be applied to highways and streets. These include the following tradeoffs: – Mobility gained in implementing peak period hard shoulder running on a freeway segments and risk associated with a disabled vehicle during the peak period. – Congestion pricing strategies on freeway segments to improve reliability and potential equity implications for lower income households. – Ramp metering strategies to preserve the quality of mainline traffic flow while at the expense of degrading mobility on adjacent local streets. – Implementing transit signal priority, bus only lane and/or queue jumps for transit vehicles along an urban corridor to improve the reliability of bus service with the potential impact of degrading mobility for side street vehicle traffic. – Implementing concrete median barriers with heights that eliminate distractions from incidents on opposing roadway lanes (“rubbernecking”) and the potential safety performance degradation by introducing a fixed object.

54 Chapter 4 – Geometric Design Elements Safety 54 Facility Type Performance MeasureDefinitionGeometric Design Elements Basic Relationship Potential Performance Tradeoffs Rural two-lane segments Crash frequency and severity Expected number of and severity of crashes Horizontal alignment, shoulder width and composition, shoulder type, lane width, type and location of auxiliary lanes, rumble strips, roadside design features, lighting, two-way left turn lane, grade See HSM Some safety improvements reduce mobility, reduce access (e.g., reducing driveway density), or negatively impact another performance measure. Rural two-lane intersection Intersection form, control type, and features, number and types of lanes, lighting, skew See HSM Rural multilane segments Shoulder width and composition, shoulder type, lane width, lane and shoulder cross slopes, median provisions, lighting, two- way left turn lane See HSM Rural multilane intersection Intersection form, control type, and features, number and types of lanes, lighting, skew See HSM

55 Chapter 4 – Geometric Design Elements Safety 55 Facility Type Performance MeasureDefinition Geometric Design Elements Basic Relationship Potential Performance Tradeoffs Urban/suburban segments Crash frequency and severity Expected number of and severity of crashes Basic cross-section,, access points and density, fixed object density, median provisions, on- street parking See HSM Some safety improvements reduce mobility, reduce access (e.g., reducing driveway density), or negatively impact another performance measure. Urban/suburban intersection Intersection form, control type, and features, number and types of lanes, signal phasing See HSM Freeway Segments Lane width, shoulder width and composition, ramp spacing, use of auxiliary lanes, ramp entrance/exit configurations See NCHRP Report Interchange Interchange form and features, number and types of lanes, horizontal alignment, cross section, roadside See NCHRP Report 17-45

56 Chapter 4 – Geometric Design Elements Opportunities to Expand Performance-Based Analysis – A key fundamental concept in performance-based analysis to inform design decisions is geometric sensitivity. – Geometric sensitivity The degree to which varying the dimensions related to a geometric element has an impact on performance. A relationship that shows an expected impact on some aspect of transportation performance as a direct result of a geometric design decision. – Level of sensitivity amount of the impact highly sensitive – number of travel lanes versus passenger car mobility less sensitive – lane width and average travel speed Certain relationships are sensitive only for certain ranges of geometric dimensions. 56

57 Chapter 4 – Geometric Design Elements Opportunities to Expand Performance-Based Analysis – NCHRP Report 687, Guidelines for Ramp and Interchange Spacing 57

58 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 58

59 Chapter 5 – Process Framework 59

60 Chapter 5 – Process Framework Project Initiation – Project Context existing site constraints current performance surrounding land uses planned improvements anticipated form and function – Intended Outcomes Clarity of the characteristics defining the current and desired future of the site; A clear and concise understanding of the primary project purpose; and A set of performance measures to be used to evaluate a design’s impact on the desired project purpose. 60

61 Chapter 5 – Process Framework Concept Development – Geometric Influences Identify the geometric characteristics that influence a project’s performance Identify the geometric characteristics or decisions influenced by the desired performance of a project. – Potential Solutions – specific awareness of the: Project context Intended outcomes Geometric characteristics and decisions 61

62 Chapter 5 – Process Framework Evaluation and Selection – Estimated Project Performance Selecting the evaluation resource – For the stage in the project development process. – Applicable to the project context – Financial Feasibility Total construction and maintenance cost Cost effectiveness Benefit/cost Ratio (B/C ratio) – Interpreting Results Estimated Project Performance Financial Feasibility 62

63 Chapter 5 – Process Framework Selection – Are the performance evaluation results making progress towards the intended project outcomes? – Do the alternatives serve the target audience and achieve the desired objectives? – Are there reasonable adjustments that can be made to the geometric design elements most significantly influencing project performance? – Do the performance measures help differentiate between the alternatives? 63

64 Chapter 5 – Process Framework Environmental Review Process – Environmental Checklist The 15-34A framework can be used to explore and consider project alternatives or adjustments to enable a project to be eligible for a Categorical Exclusion. – Environmental Assessment Project Initiation phase of the performance-based analysis framework can serve as a useful resource in developing a clear, sound, and concise project Purpose and Need statement. Concept Development and Evaluation and Selection phases of the framework are resources for developing alternatives that minimize the potential for environmental impacts. – Environmental Impact Statement The 15-34A framework can be beneficial to practitioners in developing a draft EIS, selecting a preferred alternative in the final EIS, and identifying the means to avoid and minimize environmental impacts. 64

65 NCHRP 15-34A Report Chapter 1 – Introduction Chapter 2 – Overview Chapter 3 – Identify Project Outcomes Chapter 4 – Geometric Design Elements Chapter 5 – Process Framework Chapter 6 – Case Studies/Project Examples 65

66 Chapter 6 – Case Studies/Project Examples Case Studies include a range of projects for: – Site - Area and Facility Type; – Project Development Stage; – Performance Categories, and – Project Type. 66

67 Chapter 6 – Case Studies/Project Examples 67 Case Study # Site - Area and Facility Type Project Development Stage Performance CategoriesProject Type 1 US 21/Sanderson Road - Rural Collector (Two-Lane Highway) Alternatives Identification and Evaluation Safety Intersection – Consider alternative intersection control to improve safety. 2 Richter Pass Road - Rural Collector Preliminary DesignSafety, Mobility Segment – Consider alternative horizontal curve radii to improve safety while minimizing costs and maintaining appropriate speed. 3 Cascade Ave - Suburban/Urban Arterial Preliminary Design Safety, Mobility, Reliability, Accessibility, Quality of Service Corridor – Retrofitting an existing auto- oriented urban arterial to incorporate complete street attributes. Focus on alternative street cross-sections. 4SR 4 - Rural CollectorPreliminary Design Safety, Reliability, Quality of Service Segment – Consider alternative shoulder widths and sideslopes to minimize impact to an environmentally sensitive area th Avenue - Urban Minor Arterial Alternatives Identification and Evaluation Quality of Service, Safety, Accessibility Segment – Alignment and cross-section considerations for new urban minor arterial being constructed to entice employers to a newly zoned industrial area. 6 US 6/Stonebrook Road - Rural Interchange Alternatives Identification and Evaluation Safety, Mobility Interchange - Converting an at-grade intersection to a grade-separated interchange. Focus on selecting the appropriate interchange form and location

68 Case Study #1 – US 21/Sanderson Road Alternatives identification and evaluation stage of an intersection project Rural two lane highway (i.e., rural arterial) Intended outcome - improve safety Performance category – safety – uses expected crash frequency as the primary performance metric The learning objectives of this case study include: – Illustrating the process of applying performance-based analysis; – Demonstrating the use of resources beyond typical design manuals within the project development process; and – Illustrating how a financial feasibility assessment can inform project selection. 68

69 Case Study #1 – US 21/Sanderson Road Project Initiation - Project Context Intersection Characteristics – Rural, two-lane highway (US 21) – Two-way stop controlled intersection – Primary entrance to a tribal reservation US 21 Highway - Regional east-west connection – Agricultural, undeveloped, wetlands, and low density residential – AADT is approximately 7700 vehicles per day – Posted speed is 55 mph, the 85 th percentile speed is 58 mph – Limited to no pedestrian or bicycle activity – Intersection operational level of service (LOS) is LOS B Safety Data - – Several fatal and serious injury crashes - Past 5 years 55% were angle or turning crashes 26% were rear-end crashes Failure to yield right-of-way (26% of crashes) and excessive speed (16% of crashes) Incremental solutions – adding illumination – Adding left-turn and right-turn lanes on US

70 Case Study #1 – US 21/Sanderson Road Project Initiation - Intended Outcomes 70 Tribe and the State Department of Transportation (DOT) – Initiated a study to identify additional safety projects Reduce the number and severity of crashes Enhance the intersection as the gateway to their community Accommodate a full range of motorists – agricultural equipment, logging trucks, local residents and visitors. Performance category - safety

71 Case Study #1 – US 21/Sanderson Road Concept Development 71 Design elements related to crash frequency/severity Performance TargetRelated Design ElementsRelated Design Considerations Reduce Total Number of Crashes; Reduce Severity of Crashes Intersection Control Two-way stop controlled All-way stop controlled Traffic Signal Roundabout Intersection Design Features Left-Turn Lanes Right-Turn Lanes Presence of Lighting Visibility of Intersection Increase Intersection Awareness/Visibility Cross-Sectional Elements on Intersection Approach Lane Width Rumble Strips Median (Painted or Splitter Island Type) Decrease Vehicle Speed on Intersection Approach Cross-Sectional Elements on Intersection Approach Lane Width Rumble Strips Median (Painted or Splitter Island Type) Alignment on Intersection Approach Roadway curvature Sight Distance Advanced Signing

72 Case Study #1 – US 21/Sanderson Road Concept Development The project team identified the following groupings of alternatives to explore: – Alternative intersection control; – Advanced signing and pavement markings; and – Changes in roadway cross- sectional features. 72

73 Case Study #1 – US 21/Sanderson Road Potential Solutions 73 Potential intersection configurations - to make the intersection more visible and more clearly identifiable as the main intersection to access the tribal land. – Implementing lane narrowing – Constructing a Single-Lane Roundabout; – Installing a Traffic Signal – Way-finding signs and landscaping Resources Used – AASHTO Green Book – NCHRP Report 672 Roundabouts: An Informational Guide, Second Edition – FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High-Speed Two-Lane, Two-Way Roadways – NCHRP Report 613 Guidelines for the Selection of Speed Reduction Treatments on High-Speed Intersections

74 Case Study #1 – US 21/Sanderson Road Potential Solutions Solution Development – Single Lane Roundabout 74

75 Case Study #1 – US 21/Sanderson Road Potential Solutions Design Decisions – Single Lane Roundabout – Appropriate size posted speed on US 21 design vehicles anticipated turning movement volumes – Number of entry and exit lanes on each approach anticipated turning movement volumes – Entry and exit curve radii design vehicles estimated entry, circulating and exiting vehicle speeds – Appropriate length of the splitter islands on US 21 to help make the intersection visible and support appropriate speed reduction from the roadway segment to the roundabout entry. Resource - NCHRP Report 672 Roundabout Informational Guide, Second Edition 75

76 Case Study #1 – US 21/Sanderson Road Potential Solutions Solution Development – Traffic Signal 76

77 Case Study #1 – US 21/Sanderson Road Potential Solutions Design Decisions – Traffic Signal – Appropriate length of the approach medians on US 21 to help make the intersection visible – Number of lanes and lane arrangement based on anticipated turning movement volumes – Appropriate curve radii based on design vehicles – Appropriate taper lengths and deceleration lane lengths based on posted speed 77

78 Case Study #1 – US 21/Sanderson Road Evaluation and Selection Primary intent of the project – reduce the frequency and severity of crashes Secondary consideration – incorporate way-finding and gateway treatments at the intersection Performance evaluation and financial feasibility – evaluating safety effectiveness as related to the likelihood of reducing crash frequency and severity 78

79 Case Study #1 – US 21/Sanderson Road Evaluation and Selection Estimating Performance – Design Elements Related to Crash Frequency/Severity 79 Performance Target Related Design Elements Related Design ConsiderationsTools or Resources to Evaluate Performance Reduce Total Number of Crashes; Reduce Severity of Crashes Intersection Control Two-way stop controlled All-way stop controlled Traffic Signal Roundabout Highway Safety Manual, Chapter 10 and Chapter 14 (5) Supporting Software Tools: HiSafe; IHSDM Intersection Design Features Left-Turn Lanes Right-Turn Lanes Presence of Lighting Visibility of Intersections Highway Safety Manual, Chapter 10 and Chapter 14 (5) Supporting Software Tools: HiSafe; IHSDM FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High- Speed Two-Lane, Two-Way Roadways (3) NCHRP Report 613 (4)

80 Case Study #1 – US 21/Sanderson Road Evaluation and Selection Estimating Performance – Design Elements Related to Crash Frequency/Severity 80 Performance Target Related Design Elements Related Design ConsiderationsTools or Resources to Evaluate Performance Increase Intersection Awareness/Visibility Cross-Sectional Elements Lane Width Rumble Strips Median (Painted or Splitter Island Type) FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High- Speed Two-Lane, Two-Way Roadways (3) NCHRP Report 613 (4) Decrease Vehicle Speed on Intersection Approach Cross-Sectional Elements on Intersection Approach Lane Width Rumble Strips Median (Painted or Splitter Island Type) FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High- Speed Two-Lane, Two-Way Roadways (3) NCHRP Report 613 (4) Alignment on Intersection Approach Roadway curvature Sight Distance Advanced Signing FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High- Speed Two-Lane, Two-Way Roadways (3) NCHRP Report 613 (4)

81 Case Study #1 – US 21/Sanderson Road Evaluation and Selection Incorporating Financial Feasibility – identify the relative cost effectiveness of each alternative 81 Location - Solution Expected Crashes/ Year Estimated Percent Reduction # of Crashes Mitigated/Y ear Design Life (Years) Planning Level Cost Estimate $/Crash Mitigated Over Design Life Sanderson Road Intersection TWSC- FHWA Lane Narrowing 2.231%0.75$45,000$13,196 Sanderson Road Intersection TWSC - FHWA Splitter Island 2.268%1.55$112,500$15,040 Sanderson Road- Single Lane Roundabout 2.271%1.620$3.15 million$100,832 Sanderson Road - Traffic Signal 2.236%0.820$5.61 million$354,167

82 Case Study #1 – US 21/Sanderson Road Selected Alternative Tribe and DOT decided to implement a roundabout at the US 21/Sanderson Road intersection – way-finding and gateway treatments Roundabout Alternative – Long-term potential for reducing the intersection crash frequency and severity – Opportunities for gateway treatments at and on approach to the intersection – Create definitive visual cues and changes in roadway geometry to capture motorists’ attention and aid in reducing approach speeds. 82

83 Case Study #3 – Cascade Avenue Reconstructing an existing auto-oriented urban arterial – complete street attributes – alternative street cross-sections Local business owners would like to see the corridor revitalized The learning objectives of this case study include: – Incorporating performance measures and decisions related to accommodating multiple modes; – Illustrating tradeoffs between modes considering measures beyond mobility; and – Capturing considerations and tradeoffs within a constrained physical environment. Geometric design performance categories of quality of service for multiple modes, safety, access, reliability and mobility. 83

84 Case Study #3 – Cascade Avenue Project Initiation - Project Context Cascade Avenue – Urban arterial – North-south connection between the downtown and university – AADT volume 22,000 vehicles per day – Three different fixed transit routes - 45% of riders within the City – Frequently used by bicyclists – Posted speed on Cascade Avenue is 35 mph 84

85 Case Study #3 – Cascade Avenue Intended Outcomes 85 Target audience – Business community stakeholders – Transit riders, pedestrians and bicyclists – Local residents and existing motorists Intent of the Study – Improve the road user experience – Provide access to road users not previously served – Enhance the economic vitality and activity of the street Performance categories – quality of service, safety, accessibility, reliability, and mobility Performance measures – Quality of Service – Multimodal Level of Service (MMLOS) – Safety – Crash frequency and conflict points – Accessibility – Type and presence of facilities and transit service characteristics – Mobility – Average travel time – Reliability – Consistency in travel time

86 Case Study #3 – Cascade Avenue Concept Development 86 Roadway cross-sectional elements were selected as the primary geometric elements likely to influence the performance measures – Lane width – Number of automobile through lanes – Bicycle facility presence and type – Sidewalk width – Landscaped buffer between sidewalk and travel lanes – On street parking – Bus only lanes – Central roadway median

87 Case Study #3 – Cascade Avenue Potential Solutions 87 The four basic alternatives : – Alternative 1 – Existing cross-section oriented towards serving automobiles Baseline for comparison – Alternative 2 – Transit oriented cross-section Serve transit vehicles and riders – Alternative 3 – Bicycle and pedestrian oriented cross-section Serve bicyclists and pedestrians – Alternative 4 – Hybrid of transit, bicycle and pedestrian features. Serve transit, bicyclists and pedestrians Resources Used to Develop Solutions – Urban Streets Design Guide published by the National Association of City Transportation Officials (NACTO) – NACTO’s Urban Bikeway Design Guide – AASHTO Guide for the Development of Bicycle Facilities, 4 th Edition – City’s local design guides and standards

88 Case Study #3 – Cascade Avenue Potential Solutions – Solution Development Each alternative cross-section has a modal emphasis in contrast to the existing auto-oriented cross-section A common element among the alternatives is the lack of on-street parking. – More pedestrian space – City’s goals and policies focus on projects serving person-trips rather than only auto trips – Creates concern for on-street parking in adjacent residential areas Other tradeoffs considered – allocating lanes for specific modes – Transit-only lane improve mobility and reliability for transit riders more predictable operating conditions negatively impacts mobility (and potentially reliability) for automobiles – Providing bicycle lanes and wider sidewalks for pedestrians Alternatives include a central landscaped median – documented safety benefits for autos and pedestrians – Space to implement landscaping to help improve the aesthetics of the corridor 88

89 Case Study #3 – Cascade Avenue Potential Solutions – Primary Alternative Evaluation 89

90 Case Study #3 – Cascade Avenue Potential Solutions – Primary Alternative Evaluation 90

91 Case Study #3 – Cascade Avenue Potential Solutions – Primary Alternative Evaluation Common elements across the alternatives – Falls within the existing 82 feet of right-of-way width no additional right-of-way required – Requires changing the existing curb locations revised storm water management and drainage along the corridor – Reduces the capacity for automobiles Two-lanes in each direction to one-lane in each direction – Removes on-street parking – Increases sidewalk width for pedestrians Differentiating factors across the alternatives – Amount of space designated for bicyclists – Presence of a central median – Presence of a physical buffer for pedestrians and bicyclists from motor vehicles – Type of space allocated for transit vehicles Additional critical considerations – Logistics of truck loading and unloading for the businesses – Defining transition areas on approach to intersections or major driveways Manage conflict areas within transit-only and/or bicycle lanes – Traffic control and lane configurations at intersections 91

92 Case Study #3 – Cascade Avenue Evaluation and Selection Performance categories – Safety crash frequency, crash severity, and conflict points – Mobility average travel time – Reliability Variation in travel time – Accessibility Type and facility presence and transit service characteristics – Quality of service multimodal level of service 92

93 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Summary of Resources 93 AlternativeSafetyMobilityReliabilityAccessibility Quality of Service #1 – Existing ConditionHSM, Chapter 12HCM 2010 Qualitative Assessment HCM 2010 #2 – Transit Oriented HSM, Chapter 12 Principles HCM 2010 Qualitative Assessment HCM 2010 #3 – Bicycle and Pedestrian Oriented HSM, Chapter 12 Principles HCM 2010 Qualitative Assessment HCM 2010 #4 – Hybrid of Transit, Bicycle and Pedestrian HSM, Chapter 12 Principles HCM 2010 Qualitative Assessment HCM 2010

94 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Safety – AASHTO’s HSM methodologies – Safety performance for urban/suburban arterials roadway cross- sections Cross-sections ranging from two-lane undivided to five-lanes – Estimate the long-term annual safety performance of Cascade Avenue if no changes to the cross-section were made. – Remaining features that cannot be evaluated using the HSM The transit lanes present in Alternative 2 and 4; The buffered bicycle lane present in Alternative 3; and The traditional bicycle lane in Alternative 4. Qualitative considerations based on the alternative’s ability to separate conflicting modes and provide protected space for vulnerable users. 94

95 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Mobility – Highway Capacity Manual (HCM) 2010 methodologies Average travel time from one end of Cascade Avenue to the other. – morning, mid-day and evening weekday periods – Saturday mid-day peak period. Travel time for motorists and transit vehicles 95

96 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Reliability – On-going research to develop performance measures and a means to strengthen the connection between reliability and geometric design decisions – Current approach for urban arterials Variation in travel time is the best means for estimating relative consistency for motorists and transit riders on Cascade Avenue Simulated traffic operations along the corridor 96

97 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Accessibility – Qualitative assessment of access low, moderate, or high presence of facilities for specific modes and the transit service characteristics reflected in each alternative. 97

98 Case Study #3 – Cascade Avenue Evaluation and Selection Estimating Performance – Quality of Service – Multimodal Level of Service (MMLOS) - HCM 2010 Provides a letter grade A through F to indicate the quality of the travel experience from specific road users’ perspective. May result in one street cross-section having different quality of experiences depending on whether a person is walking, biking, taking transit or driving an automobile. Captures some of the benefits from project elements the HSM cannot; such as bicycle lanes. 98

99 Case Study #3 – Cascade Avenue Evaluation and Selection Performance Evaluation Results 99 AlternativeSafety Mobility: Average Travel Time (min) Reliability: Variation in Travel TimeAccessibility Quality of Service: MMLOS #1 – Existing Condition PedestrianLow-- D BicycleLow-- F TransitLow to 5.26ModerateD AutoLow to 3.17HighA #2 – Transit Oriented PedestrianHigh--ModerateC BicycleModerate-- E TransitHigh to 4.76HighB AutoHigh to 3.60LowC #3 – Bicycle and Pedestrian Oriented PedestrianHigh-- B BicycleHigh-- C TransitHigh to 6.00ModerateD AutoHigh to 6.10LowD #4 – Hybrid of Transit, Bicycle and Pedestrian PedestrianLow--ModerateC BicycleModerate-- D TransitModerate to 4.78HighB AutoLow to 3.56LowC

100 Case Study #3 – Cascade Avenue Evaluation and Selection Incorporating Financial Feasibility – identify the relative cost effectiveness of each alternative 100 AlternativeCost per Mile Alternative #1 – Existing Condition$0 Alternative #2 – Transit Oriented$1.4 million Alternative #3 – Bicycle and Pedestrian Oriented$1.6 million Alternative #4 – Hybrid of Transit, Bicycle and Pedestrian$1.0 million

101 Case Study #3 – Cascade Avenue Selected Alternative City and project stakeholders - Alternative 2 – provides improved safety, reliability, access, and quality of service for transit riders, pedestrians and bicyclists. Local business community - Alternative 3 – City plans to integrate Alternative 3 attributes into Alternative 2 landscaping along the sidewalks characteristics to better serve bicyclists 101

102 NCHRP 15-34A Report Summary Performance-based analysis of geometric design – principles-focused approach that looks at the outcomes of design decisions as the primary measure of design effectiveness. Geometric Design Performance Categories – Accessibility, Mobility, Quality of Service, Reliability, Safety Process Framework – Project Initiation – Project Context and Intended Outcomes – Concept Development – Geometric Influences and Potential Solutions – Evaluation – Estimated Performance and Financial Feasibility – Selected Alternative 102

103 Presentation Outline Project Background and Overview Information Gathering Project Work Plan NCHRP Report 103

104 NCHRP 15-34A: Performance-Based Analysis of Geometric Design of Highways and Streets Questions? Brian Erin Richard J. Porter 104


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