Performance-Based Analysis of Geometric Design of Highways 1 and Streets 2 3 4 5 Brian L. Ray, P.E. (corresponding author) 6 Kittelson & Associates, Inc. 7 610 SW Alder Street, Suite 700 8 Portland, OR 97205 9 PHONE: (503) 228-5230 10 FAX: (503) 273-8169 11 EMAIL: [email protected]12 13 Erin M. Ferguson, P.E. 14 Kittelson & Associates, Inc. 15 155 Grand Avenue, Suite 900 16 Oakland, CA 94612 17 PHONE: (510) 433-8066 18 FAX: (510) 839-0871 19 EMAIL: [email protected]20 21 Julia K. Knudsen, P.E. 22 Kittelson & Associates, Inc. 23 610 SW Alder Street, Suite 700 24 Portland, OR 97205 25 PHONE: (503) 228-5230 26 FAX: (503) 273-8169 27 EMAIL: [email protected]28 29 30 31 32 33 34 35 36 37 38 SUBMISSION DATE: November 8, 2014 39 40 WORD COUNT: 5858 41 42 NUMBER OF EXHIBITS: 6 = 1500 words 43 44 TOTAL WORD COUNT (including 250 words per exhibit): 7358 45 46
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Performance-Based Analysis of Geometric Design of Highways 1
The framework can be used throughout the stages of the project development process and within or outside 1
of an environmental review process. The project development stage can help guide the specific 2
considerations for each step in the framework. As shown in Exhibit 2, the framework is organized into 3
three broad phases including: 1) Project Initiation; 2) Concept Development; and 3) Evaluation and 4
Selection. 5
These contain activities to meet the needs of each phase and build incrementally through the steps needed 6
to initiate a project, develop concepts, evaluate options, and ultimately select or advance a project or design 7
recommendations. 8
The Project Initiation phase sets a foundation for understanding the project context and overarching 9
intended outcomes. Understanding the project context may be accomplished through examining existing 10
site constraints, reviewing current performance related to operations, safety, access, reliability and quality 11
of service, and identifying the surrounding land uses and future planned improvements. Outlining the 12
intended project outcomes can be achieved through understanding the motivations for a project, identifying 13
the target audience and desired performance characteristics. The goal of the Project Initiation phase is to 14
identify a clear understanding of the project purpose and the characteristics defining the current and desired 15
future of the project site. This information will lead help develop to a clear a set of performance measures 16
to be used to evaluate a design’s impact on the desired project purpose. 17
Concept Development focuses on developing potential solutions to address the intended project outcome 18
and may include evaluating discrete design decisions of a geometric element or configuration. At the 19
beginning stages of the project development process, Concept Development will include identifying 20
overarching alternatives, such as alternative intersection forms, roadway alignments, roadway cross-21
sections, or interchange forms. During later stages of the project development process, Concept 22
Development becomes more detailed, focusing on specific solutions, such as adjusting a horizontal curve. 23
Regardless of the project development stage, within the Concept Development phase there are geometric 24
features that will influence the performance of the ultimate roadway facility and a set of potential solutions 25
whose resulting performance can be evaluated to help determine which solution is preferred. Geometric 26
influences are the geometric characteristics or decisions that can influence a project’s performance as it 27
relates to the categories of Accessibility; Mobility; Quality of Service; Reliability; and Safety. It also 28
includes geometric characteristics or decisions influenced by the desired performance of a project. The 29
information is essential in developing potential solutions that make progress towards the intended project 30
outcomes. 31
The Evaluation and Selection phase uses the potential solutions outlined in the Concept Development 32
phase to directly integrate performance-based analysis to further refine those solutions. The two primary 33
steps within this phase include estimating performance and financial feasibility of a potential project. The 34
performance of a project is evaluated relative to the previously identified performance categories and 35
associated measures. Next, the financial feasibility of each alternative is considered to decide if there is an 36
alternative that sufficiently meets the project’s intended outcome and is financially feasible. This phase will 37
result in one of the following two outcomes: 1) Return to the Concept Development phase for further 38
solution development or refinement; or 2) A selected project. 39
Based on the results from the estimated performance and financial feasibility step described in the 40
Evaluation and Selection phase, a preferred alternative is selected or the project team may decide to 41
further refine alternatives and re-evaluate their performance. While there may be other external factors or 42
qualitative performance measures driving the decision to select a preferred alternative or further refine and 43
re-evaluate alternatives, there are some key questions that may help identify how to best advance a project 44
to the next stage in the project development process. These questions may include: 45
Are the performance evaluation results making progress towards the intended project 46
outcomes? 47
Do the alternatives serve the target audience and achieve the desired objectives? 48
Ray, Ferguson and Knudsen 9
Can reasonable adjustments be made to the geometric design elements most significantly 1
influencing project performance? 2
Do the performance measures help differentiate between the alternatives? 3
As noted previously, the framework can be used within or outside of an environmental review process. The 4
performance-based analysis framework can benefit practitioners in developing a draft EIS, selecting a 5
preferred alternative in the final EIS, and identifying the means to avoid and minimize environmental 6
impacts. The Project Initiation phase can be used to develop a clear and focused project purpose and need 7
statement. The Concept Development and Evaluation and Selection phases can be used to develop 8
reasonable alternatives that perform to a level to fulfill the project purpose and need while avoiding or 9
minimizing environmental impacts. The Evaluation and Selection phase can also be used to help identify 10
the preferred alternative. The overall performance-based analysis framework can also be used to facilitate 11
the comprehensive documentation needed within the EIS process. 12
Application 13
The performance-based analysis to inform geometric design decisions can be integrated into a wide range 14
of projects and tailored to fit the context of what the project team is striving to achieve. Chapter 6 of 15
NCHRP Report 785 presents a series of project examples illustrating how transportation professionals can 16
use the performance-based analysis framework across urban, suburban, and rural contexts for intersection 17
design considerations, streets, highways, and freeway and interchange system planning (3). Exhibit 3 18
summarizes the example projects contained in Chapter 6 of NCHRP Report 785 (3). 19
Exhibit 3. Summary of Project Examples in NCHRP Report 785. 20
Project Example
Site - Area and Facility Type
Project Development
Stage Performance Categories Project 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 Design
Safety 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.
4 SR 4 - Rural Collector Preliminary Design
Safety Reliability Quality of Service
Segment – Consider alternative shoulder widths and sideslopes to minimize impact to an environmentally sensitive area.
5 27th 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 rural
intersection to a grade-separated interchange.
Focus on selecting the appropriate interchange form and location (e.g., spacing considerations).
Source: NCHRP Report 785 (3) 21
Ray, Ferguson and Knudsen 10
The project examples were developed from actual projects that have integrated performance-based analysis 1
into design decisions and/or could have benefited from incorporating performance-based analysis into 2
design decisions. Some of the project examples were created to illustrate performance-based analysis 3
process and communicate key learning objectives. In each project example, the names are changed and do 4
not reflect the actual names of the facilities or agencies. 5
The following sub-sections provide a synopsis of three of the six project examples. The three project 6
examples that are touched on below address rural and urban contexts; application to intersections and 7
roadway segments; consider changes in roadway cross-section, intersection traffic control and roadway 8
alignment; address multiple performance categories; and include multiple modes. 9
Project Example 1: US 21/Sanderson Road Intersection 10
The US 21/Sanderson Road intersection example illustrates how the performance-based analysis 11
framework can be integrated into evaluations and decisions considered when evaluating alternative 12
intersection traffic control. This particular intersection is located on a rural two-lane roadway with a posted 13
of 55 mph. 14
The project example discusses the project context and defines the intended project outcomes. The outcomes 15
are focused on improving safety and enhancing the intersection to be a gateway to the adjacent community. 16
Safety is the primary performance category of interest within this project. Based on these intended 17
outcomes, a set of performance targets (e.g., reducing severe crashes) and related geometric design 18
decisions (e.g., intersection control) are identified. These help inform the project team in identifying and 19
developing potential solutions for the intersection. The alternatives considered for the intersection were: 1) 20
Single-lane roundabout (Exhibit 4); and 2) Traffic signal (Exhibit 4); and 3) Low-cost pavement marking 21
and signing enhancements to the existing two-way stop controlled intersection. Using performance analysis 22
resources such as the Highway Safety Manual (HSM) (14), the project example illustrates the expected 23
crash performance at the intersection with the different traffic control designs. It includes planning level 24
cost estimates to be able to gauge the cost effectiveness of the alternatives by calculating the cost per crash 25
mitigated over the design life of each alternative. 26
Exhibit 4. Roundabout Concept and Traffic Signal Concept. 27
Source: NCHRP Report 785 (3) 28
From the performance-based analysis process and results, the project team, including the agencies 29
involved, was able to objectively and quantitatively consider the relative safety performance of the different 30
alternatives relative to their costs. Based on this comparison, they selected the roundabout alternative in 31
combination with way-finding and gateway treatments. The application of performance-based analysis in 32
this project example is readily transferable to intersection design and traffic control feasibility studies in 33
other rural contexts, urban areas, and suburban communities. It can also be expanded to include other 34
Ray, Ferguson and Knudsen 11
performance measures discussed in NCHRP Report 785 such as mobility, quality of service for different 1
modes of travel, and accessibility (3). 2
Project Example #2: Richter Pass Road 3
The Richter Pass Road example illustrates incorporating performance-based analysis into a corridor study 4
for a rural two-lane roadway where surrounding land uses have evolved from rural to increasingly 5
suburban. The roadway traverses a hillside that has experienced increasing amounts of residential 6
development adjacent to the roadway and accessing the roadway. The roadway frequently has steep side 7
slopes with drop offs on one side and retaining walls or cuts through rock on the other side of the roadway. 8
The corridor has experienced a steady increase in traffic volume as well as crashes. 9
The project example discusses the project context and highlights the low-cost treatments previously 10
implemented along Richter Pass Road. A defining feature of the roadway is that the original design speed is 11
55 mph, the posted speed is 45 mph, and there are advisory speed signs for horizontal curves along the 12
roadway for as low as 15 mph. The topography the roadway traverses and the resulting alignment does not 13
create a consistent or predictable roadway for motorists. The intended project outcomes are focused on 14
reducing crash frequency and severity while maintaining a reasonable level of mobility the commuter 15