Performance Based Analysis & Practical Design

Performance Based Analysis in support of “practical design” solutions Transportation Education Series April 15, 2010 John M. Mason, PhD, PE Brian L. Ray, PE

Presentation Outline What is “practical design”? “ Standards” and practical design Performance based tools Design variances and documentation Discussion

What is “practical design”? A response to project budget and program funding issues that attempts to: Generally do more with less money Better tailor solutions to the project purpose and need Complete “good” projects not “GREAT” projects Consider less than long term solutions Focus on the benefits gained over existing versus gaps to the “ideal” project Provide flexibility in the defining design solutions Resources: Derived from MODOT, ITD, PENNDOT, ODOT

What “practical design” IS NOT! “Value Engineering” on steroids Marginal long range plan chopped back to meet budget “Full standards” on as much as we can afford Long range forecast needs interpolated back to nearer term needs Proposing nearer term plan based on long term versus current needs Neglecting long term needs and considerations Designing inflexible solutions Proposing solutions that preclude future flexibility and opportunities Discarding fundamental operations, design, and safety principles just to be “practical” Practical solutions may be simpler but require more care and thought than traditional approaches

Who is doing “practical design”? Many states are initiating or exploring practical design programs Missouri DOT (2005) PennDOT (Smart transportation 2005) Kentucky Transportation Cabinet Minnesota DOT Idaho Transportation Department Oregon DOT (2010) Others? This is just the beginning…

What are key elements of “practical design”? Common themes among states Continued emphasis on “Safety” Increased emphasis on project scoping Project teams Stakeholder engagement Better defining the project context Focus on the “system” or “network” Reducing Costs Focusing spending where it’s most effective Flexible approaches to design solutions Documentation, documentation, documentation

What are key examples of “practical design”? Missouri DOT 15 miles of roadway and shoulder improvement versus traditional typical section for fewer miles.

What are key examples of “practical design”? Missouri DOT Reduced fatalities by focusing on high risk areas versus “chasing” crashes around the state

What are key examples of “practical design”? PennDOT Consider lower cost but high value projects even if they are not the “ultimate fix”

What are “standards”? Uniform approaches to provide consistency in design Tools to match criteria to similar design environments Representative approaches that represent the standards of care of our profession What else?

What are “standards”? “ Standards” have become safety surrogates Are the following true? If it meets standards it must be safe If it doesn’t meet standards it is not as safe If there is no standard for it, it must not be allowable If a design exception is needed it must be “bad” … but what is the research behind our standards?

What are the origins of our “standards”? Late 1930s and 1940s Bureau of Public Roads and AASHO Looking for uniformity on roadway designs No research done to establish “standards of care” A synthesis of practical knowledge to address issues i.e., Physics to cover vehicles in motion on a curve “Pamphlets” based on consensus of the practice Compiled in a 3 ring notebooks These were combined to form “policies” based on committees, agency leaders, and professionals consensus of the practice

AASHTO (AASHO) Geometric Design Policies Title Year Policy on Criteria for Marking, Signing No-Passing-Zones on Two- and Three-Lane Roads 1940 A Policy on Sight Distance for Highways 1940 A Policy on Highway Types (Geometric) 1940 A Policy on Highway Classifications 1938

AASHTO (AASHO) Geometric Design Policies Design Standards: Interstate System, Primary System, and Secondary and Feeder Roads 1945 A Policy on Grade Separations for Intersecting Highways 1944 A Policy on Rotary Intersections 1941 A Policy on Intersections at Grade 1940 Title Year

What are the origins of our “standards”? Late 1950s and 1970s Interstate system founded on military applications Pavement studies Roadway clearances Bridge capacities Initially primarily focused on rural design (“blue book”) but urban freeways and arterials needs expanded (“red book”) Need for consistency in interstate system led to policies that were still not based on research

AASHTO (AASHO) Geometric Design Policies A Policy on Design of Urban Highways and Arterial Streets 1973 A Policy on Arterial Highways in Urban Areas 1957 A Policy on Geometric Design of Rural Highways 1954 1965 Policies on Geometric Highway Design 1950 Title Year

What are the origins of our “standards”? 1980s The origins of AASHTO’s “Green Book” Combine “Blue Book” and “Red Book” “ Purple Book” at that time was for 3-R Guidance Hence the birth of the “Green Book” in 1984 1980s-1990s NCHRP research efforts on new and emerging topics; exploring basis of some existing topics (i.e., SSD) 2000’s Numerous supplemental guidance documents for topics of interest.

AASHTO (AASHO) Geometric Design Policies A Policy on Design Standards – Interstate System 1991 2005 Guidelines for the Geometric Design of Very Low Volume Local Roads (ADT≤400) 2001 A Policy on Geometric Design of Highways and Streets 1984 1990 1994 2001 2004 Title Year

AASHTO (AASHO) Geometric Design Policies Highway Capacity Manual, Special Report 209 (TRB) 2000 Prediction of the Expected Safety Performance of Rural Two-Lane Highways. Report No. FHWA-RD-99-207 2000 Speed Prediction for Two-lane Rural Highways. Report No. FHWA-RD-99-171, Federal Highway Administration 1999 NCHRP Report 279: Intersection Channelization Design Guide 1985 Title Year

AASHTO (AASHO) Geometric Design Policies Neighborhood Street Design Guidelines: An ITE Proposed Recommended Practice (ITE) 2003 Transportation and Land Development (ITE) 2002 Geometric Design Criteria for Highway-Rail Intersections (Grade Crossings) [ITE] 2001 Roundabouts: An Informational Guide (FHWA) 2000 Title Year

AASHTO (AASHO) Geometric Design Policies Geometric Design Handbook: Freeway and Interchange Design (ITE) 2005 Context Sensitive Solutions in Designing Major Urban Thoroughfares for Walkable Communities: An ITE Proposed Recommended Practice (ITE) 2005 Signalized Intersections: Informational Guide (FHWA) 2004 Access Management Manual, Transportation Research Board 2003 Title Year

What if we can’t meet “standards”? Employ your “engineering judgment” Look for flexible approaches to design values Apply fundamental operations and design principles for that condition Evaluate and understand safety and operational trade offs of our choices Document our decisions

Missouri DOT Practical Design Implementation “ Primary Guidance”—Overarching considerations “ Discussion”—Information to support choices Addressing: Type of Facility Typical Section Elements Horizontal and Vertical Alignment Pavements Structures & Hydraulics Roadside Safety Incidental/Misc.

Performance based applications aren’t new… Aeronautical engineering Pavement management systems Concrete and steel design Traffic operations Design consistency and operational uniformity

Operational Performance Tools Operational performance tools you probably know : HCM CORSIM Synchro/Sim Traffic VISSIM Traffic Analysis Module of IHSDM Operational/Reliability Analysis – SHRP2 …… but what about design tools?

Performance Based Concepts Operation uniformity to test design consistency 4.10 ft/sec 6.56 ft/sec ∆ V85 > 12 mph Poor 2.92 to 4.10 ft/sec 4.85 to 6.56 ft/sec 12mph ≥ ∆V85 ≥ 6 mph Fair 1.77 to 2.92 ft/sec 3.28 to 4.85 ft/sec ∆ V85 ≤ 6mph Good Acceleration Rate Deceleration Rate Speed Change Rating

Performance Based Applications FHWA, Exhibit 6-2, p. 131 Roundabouts employ an iterative design process to optimize safety and operations Typical “linear” process

Performance Based Applications Roundabout performance objectives: Low speed on entry: less than 30 mph Low and consistent speeds between geometric elements: less than 12 mph Low relative speeds between conflicting traffic streams.

Performance Based Tools IHSDM: Design Consistency Module Output

Performance Based Concepts IHSDM HSM Base Models Accident Modification Factors Estimates predicted number of crashes/year The evolution of safety tools:

IHSDM Crash Prediction Module Output

Performance Based Concepts Highway Safety Manual (HSM) Available in late 2010 Will contain: Predictive Methods Accident Modification Factors “Principles” of HSM can be applied now and could support Practical Design solutions

Part A – Introduction and Fundamentals 1: Introduction 2: Human Factors 3: Fundamentals Part B – Roadway Safety Management 4: Network Screening 5: Diagnosis 6: Select Countermeasures 7: Economic Evaluation 8 Prioritization 9: Safety Effectiveness Evaluation Part C – Predictive Method 10: Two-Lane Rural Highways 11: Multilane Rural Highways 12: Urban and Suburban Arterials Part D – Accident Modification Factors 13: Roadway Segments 14: Intersections 15: Interchanges 16: Special Facilities 17: Networks Glossary HSM Content

Performance Based Concepts Objectives & Scope: Developing a guide for conducting performance-based designs throughout project development Considers each stage of the project development process. NCHRP Project 15-34: Performance-Based Analysis of Geometric Design of Highways & Streets

Performance based applications for Practical Design Solutions: Corridor Case Study Intersection Evaluation

Airport Way Improvements Reconnaissance Study “ Practical solutions for an evolving corridor” Fairbanks, Alaska

Arterial Corridor with Frontage Roads

Vision Concepts: Freeways to Unlimited Access Balance between Mobility & Access

Evaluating and screening solution concepts

Selecting recommended alternatives

Vision Concepts, Concepts, Alternatives Initial Concepts Most-Promising Alternatives Refined Concepts Applying the same evaluation criteria consistently with increasingly detailed evaluations on fewer solutions

OR 34 at Seven Mile Lane Intersection Design Study “ Considering solutions within available project funding” Linn County, Oregon

Project Location OR 34 – Regional Highway Seven Mile Lane – Major Collector Half mile east of I-5/OR 34 interchange Two-way stop controlled Operates at LOS “F” Signal warrants 1 and 2 satisfied for 2008 traffic conditions Linn County ODOT

Comparing the two alternatives Less impact to traffic More impact to traffic Construction $650,000 to $800,000 $1,500,000 to $1,800,000 Cost Acceptable Not Acceptable 2030 Traffic Conditions Acceptable Acceptable 2008 Traffic Conditions Considerations

Comparing safety qualitatively Minor and major crashes Minor crashes More severe crashes Less severe crashes High, variable speeds Lower, consistent speeds Multiple decision points Simplified decision making 32 vehicle conflict points 8 vehicle conflict points

Outcomes Linn County continued forward with the original signalized plan Some of their considerations The signal better served the predominant State Highway through volumes The improvements are needed immediately and conducting a redesign would delay the much needed project Construction costs are a significant factor for this rural county The qualitative safety benefits of the roundabout did not outweigh the operational and cost considerations

Performance Based Tools Applying the Highway Safety Manual to practical design solutions Two examples: Using HSM “predictive methods” to support alternatives cross section design evaluations Considering Accident Modification factors in design decisions

Part C – Predictive Method 10: Two-Lane Rural Highways 11: Multilane Rural Highways 12: Urban and Suburban Arterials Part D – Accident Modification Factors 13: Roadway Segments 14: Intersections 15: Interchanges 16: Special Facilities 17: Networks Glossary Part A – Introduction and Fundamentals 1: Introduction 2: Human Factors 3: Fundamentals Part B – Roadway Safety Management 4: Network Screening 5: Diagnosis 6: Select Countermeasures 7: Economic Evaluation 8 Prioritization 9: Safety Effectiveness Evaluation HSM Content

Predicting Safety for Alternative Cross Sections Condition 1: Existing Cross Section Condition 2: Alternative Cross Section Photo Courtesy of Yolanda Takesian

Performance Based Concepts Select SPF and estimate base conditions Apply AMFs to modify base conditions to site specific conditions Apply calibration factor Apply EB when appropriate N i = SPF *(AMF 1i *AMF 2i )*Ci Using predictive safety Performance to evaluate design alternatives

Performance Based Predictive Safety Results Future No Build Condition Future Alternative Condition N rs = 41 crashes/year N rs = 36 crashes/year Photo Courtesy of Yolanda Takesian

Part C – Predictive Method 10: Two-Lane Rural Highways 11: Multilane Rural Highways 12: Urban and Suburban Arterials Part D – Accident Modification Factors 13: Roadway Segments 14: Intersections 15: Interchanges 16: Special Facilities 17: Networks Glossary Part A – Introduction and Fundamentals 1: Introduction 2: Human Factors 3: Fundamentals Part B – Roadway Safety Management 4: Network Screening 5: Diagnosis 6: Select Countermeasures 7: Economic Evaluation 8 Prioritization 9: Safety Effectiveness Evaluation Highway Safety Manual

Performance Based Predictive Safety Results Horizontal Curve Design: Scenario: How do we use the Highway Safety Manual to support flexible design approaches to minimizing cost and impacts? Modify curve radius and transitions “ Add” advisory signage support the design of modified curve and radius and transitions

Horizontal Alignment AMFs: Modify Horizontal Curve Radius and Length, and Provide Spiral Transitions Applies to: Rural Two-Lane Roads The probability of an accident generally decreases with longer curve radii, longer horizontal curve length, and the presence of spiral transitions. Where, Lc= Length of horizontal curve including length of spiral transitions, if present (mi) R= Radius of curvature (ft) S= 1 if spiral transition curve is present; 0 if spiral transition curve is not present

Horizontal Alignment AMFs: Install Combination Horizontal alignment/ Advisory Speed Signs Applies to: Rural Two-Lane Roads, Rural multi-lane highways, Expressways, Freeways, Urban and suburban arterials Combination horizontal alignment/advisory speed signs are installed prior to a change in the horizontal alignment to indicate that drivers need to reduce speed. Potential Crash Effects of Installing Combination Horizontal Alignment/ Advisory Speed Signs (W1-1a, W1-2a)

Design Variances and Documentation We will cover… Practical Design and Risk Risk Management Design Variances

Practical Design and Risk Chief Engineer Implemented initiative without seeking legal council Implemented practical design WITHOUT guidance documents Told staff to design what they NEED not based on the criteria Legal Council “ Acceptable engineering practice” is focal consideration in court Using “engineering judgment” is less risk than “ I followed the standards” “ I followed the standards” is not as strong a defense as it used to be How did/does MODOT approach practical design?

Practical Design and Risk Management Let’s get this out of the way... You are always at risk of being sued…… “ Full” Standards “ Context Sensitive Solutions” “ Practical Design” … The key is to not be “negligent”

Practical Design and Risk Management An agency can manage risk by having: Appropriate and defined management structures Well defined project development processes Well defined design criteria Clear design decision making practices Consistent documentation practices.

Practical Design and Risk Management Best Practices for Risk Management Consider multiple alternatives Evaluate and document design decisions Maintain control over design decision making Demonstrate a commitment to mitigate safety concerns Monitor design exceptions to improve decision making Document, Document, Document!

What is a design variance or “exception”? Transportation Agencies prepare design & construction plans. Typical Goal is: Safety, Efficiency, Economic It is not always practical to meet design standards. Typical Goal is: Reduce costs or minimize impacts Design variance is an is deviation from criteria. FHWA (13 controlling criteria) or Agency Design variances require a process to document the “design exception”

Design Exception Issues Right of Way Construction Costs Environmental Impacts Historic/Scenic Preservation Safety Traffic Operations

13 FHWA Controlling Criteria Design Speed Lane Width Shoulder Width Bridge Width Structural Capacity Horizontal Alignment Vertical Alignment Grade Stopping Sight Distance Cross Slope Superelevation Vertical Clearance Horizontal Clearance (other than clear zone) But does meeting criteria values make a project safe? Or…. Are these criteria “surrogates” for safety?

Most Common Design Deviations/Variances Source: NCHRP Synthesis 316 Design Exception Practices

FHWA Controlling Criteria and the HSM 1. Design Speed 2. Lane Width 3. Shoulder Width 4. Bridge Width 5. Structured Capacity 6. Horizontal Alignment 7. Vertical Alignment 8. Grade 9. Stopping Sight Distance 10. Cross Slope 11. Superelevation 12. Vertical Clearance 13. Horizontal Clearance Of these criteria in the HSM, what information do we really know about them?

13 FHWA Controlling Criteria: AMFs and Trends by Facility Types

Applying the HSM to support the OR 213 Design Exception request Oregon City, Oregon

Objective To provide additional safety information to support a Design Exception request To address concerns regarding the potential safety impacts of: Reduced lane widths Shoulder/Shy distance Median

Constrained bridge cross section

Reduce dimensions and add a NB lane

Assessing Safety What are the potential safety impacts of the modified cross section on OR 213? Apply NCHRP 17-36: First Edition the Highway Safety Manual (HSM) Accident Modification Factors (AMF) Adding lanes to a freeway by narrowing existing lanes and shoulders, and maintaining existing right-of-way * The treatment could result in benefit, disbenefit, or no safety effect based on standard deviation

HSM applications for predicted crashes Five to six lane conversion by narrowing existing lanes and shoulders AMF = 1.03 (standard deviation 0.08) 0.95 to 1.11 (1.03 +/- 0.08) Average crashes per year OR 213 at the bridge = 2.0 Impact to yearly crashes decrease to 1.9 crashes per year OR increase to 2.2 crashes per year What type of crashes? How significant are they?

Considering potential mitigation strategies Median Barrier “ Positive benefit” – no specific AMF Roadway illumination AMF = 0.72 for injury crashes AMF = 0.83 for non-injury crashes Continuous rolled-in shoulder rumble strips on shoulder AMF = 0.82 Do we need to “mitigate” if we don’t know if there is or isn’t a “problem”? Monitor and then take action if needed?

Analysis Summary 2.00 1.60 1.70 1.40 0.92 0.72 0.10 0.82 Single-veh run-off-road, all severities Install Continuous Rolled Rumble Strips on Shoulder 2.00 1.70 1.70 1.40 0.90 0.76 0.07 0.83 All types, nighttime, non-injury Install Illumination 1.70 1.50 1.50 1.30 0.78 0.66 0.06 0.72 All types, nighttime, nonfatal, injury 2.20 1.90 1.11 0.95 0.08 1.03 All types, all severities Maintain Existing ROW, Add Lanes by Narrowing Existing Lanes and Shoulders 2.00 n/a n/a n/a All types, all severities Maintain Existing Cross Section OR 213 Annual Crash Frequency AMF Range Std Dev AMF Accident Type/Severity Treatment Description

Conclusions supporting design decisions The proposed modifications does NOT demonstrate a significant increase in crash frequency If additional safety mitigation strategies are applied a reduction in crash frequency is likely

Closing thoughts—Integrating Safety and Operations The quantitative (predictive) safety analysis is at its infancy and there are many opportunities to engage Operations and safety performance-based evaluations offer a means of tailoring solutions to meet practical design and context sensitive solutions needs New tools can support practical design decision making: SafetyAnalyst IHSDM FHWA Crash Reduction Factor Desktop Reference

Closing thoughts-- Performance Based Evaluations Supporting Practical Design Our profession is moving towards performance-based planning and design The profession now has the ability to begin to more fully integrate operations and safety into the design decision process We have a responsibility to understand what we know…and what we don’t… about the tools we apply The tools and concepts that support those tools can guide and support practical design approaches to transportation solutions

Performance Based Analysis & Practical Design

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