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From page 61... ... 61 C H A P T E R 6 6.1 Introduction These project examples are intended to help users apply the concepts, models, and performance evaluation framework element presented in Chapters 1 through 5. The project examples are based on a variety of specific projects, amalgams of projects, or project considerations that can be commonly found in practice. Read the entire page →
From page 62... ... 62 Performance-Based Analysis of Geometric Design of Highways and Streets 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. Read the entire page →
From page 63... ... Project Examples 63 information regarding the actions and considerations within each stage of the framework. Chapter 3 provided an overview of project performance categories and associated performance measures that might be used in evaluating project solutions. Read the entire page →
From page 64... ... 64 Performance-Based Analysis of Geometric Design of Highways and Streets 6.2.1.2 Intended Project Outcomes Authors' Note: The following summarizes the key information related to whom the project is intended to serve, what the project is intended to achieve (i.e., intended project outcome) , the applicable project performance category (or categories) Read the entire page →
From page 65... ... Project Examples 65 Identifying the design elements with the potential to influence crash frequency and severity serves as a starting place for brainstorming and exploring potential solutions. For example, there may be types of solutions that form a single alternative or a solution set that could be common across each alternative. Read the entire page →
From page 66... ... 66 Performance-Based Analysis of Geometric Design of Highways and Streets visible and more clearly identifiable as the main intersection to access the tribal land. This project considered the following: • Implementing lane narrowing -- pavement markings and rumble strips consistent with FHWA publications on low-cost treatment (see reference below) Read the entire page →
From page 67... ... Project Examples 67 wayfinding and related additional elements are an example of solution types that could be transferable across broader alternatives to help achieve project goals. The design decisions reflected in Exhibit 6-4 include the following: • Appropriate size (e.g., inscribed circle diameter) Read the entire page →
From page 68... ... 68 Performance-Based Analysis of Geometric Design of Highways and Streets Similar to the roundabout alternative, the key reasons for considering these design elements in the alternatives development and evaluation stage is to determine their impact on performance (safety and operations) , assess the feasibility of the traffic signal, and estimate potential rightof-way impacts of the alternative. Read the entire page →
From page 69... ... Project Examples 69 this project, the cost per mitigated crash was used as the performance measure to gauge the relative economic performance for an alternative. The evaluation did not quantify the potential benefits of reduced vehicle speeds, the wayfinding, or the gateway treatments because it is not currently possible to relate those attributes directly to anticipated reduction in crash frequency. Read the entire page →
From page 70... ... 70 Performance-Based Analysis of Geometric Design of Highways and Streets 6.2.3.2 Selected Alternative Authors' Note: Section 5.4.2 presents considerations with respect to selecting a preferred project alternative or determining the appropriate specific geometric design decisions (e.g., radius of a horizontal curve) Read the entire page →
From page 71... ... Project Examples 71 • Use Speed Concepts and the concept of inferred speed in informing design decisions • Illustrate the design flexibility agencies have to not select the alternative with the lowest predicted number of crashes 6.3.1 Project Initiation 6.3.1.1 Project Context Authors' Note: Using the considerations noted in Section 5.2.1, we are able to identify key characteristics of the project context likely to help inform the intended project outcomes, performance category, and performance measures we will use to develop and evaluate potential solutions. The following summary of the project context sets the foundation for the remaining activities within the performance-based analysis framework. Read the entire page →
From page 72... ... 72 Performance-Based Analysis of Geometric Design of Highways and Streets With the steady increase in traffic volume along the roadway, there has also been an increase in crashes. The majority of crashes, approximately 72% within the last 3 years, were run-off-theroad crashes. Read the entire page →
From page 73... ... Project Examples 73 performance categories, and supporting performance measures. In this project example, safety and mobility are the performance categories of interest. Read the entire page →
From page 74... ... 74 Performance-Based Analysis of Geometric Design of Highways and Streets The critical balancing act in developing potential solutions for Richter Pass Road, and ultimately selecting the preferred solution, will be the project costs. The terrain and topography through which Richter Pass Road passes likely necessitates cut, fill, and retaining walls for nearly any change in horizontal alignment or shoulder width. Read the entire page →
From page 75... ... Project Examples 75 benefit. If an investment is made to add shoulder width, the county and DOT would like to see sufficient shoulder width to enable a disabled vehicle to pull to the side and leave a total of 22 ft available for other motorists to pass and incident response activities. Read the entire page →
From page 76... ... 76 Performance-Based Analysis of Geometric Design of Highways and Streets values of a shoulder width of 4 ft and the horizontal curve radius, length, and superelevation for 35 mph (for Alternative 3) and 55 mph (for Alternatives 2 and 4) Read the entire page →
From page 77... ... Project Examples 77 are key characteristics of the horizontal alignment in Alternative 2. This corresponds to higher inferred speeds, lower predicted crashes, higher cut/fill volumes, and higher construction costs relative to Alternative 3. Read the entire page →
From page 78... ... 78 Performance-Based Analysis of Geometric Design of Highways and Streets 6.3.3 Evaluation and Selection 6.3.3.1 Estimated Performance and Financial Feasibility Authors' Note: Sections 5.4 and 5.4.1 provide information and considerations regarding (1) how to estimate the performance of project alternatives or specific geometric design decisions and (2) Read the entire page →
From page 79... ... Project Examples 79 Incorporating Financial Feasibility. The project team developed cost estimates for each alternative. Read the entire page →
From page 80... ... 80 Performance-Based Analysis of Geometric Design of Highways and Streets and mobility performance goals at a financially feasible level of investment. The agencies were able to look beyond the traditional approach (i.e., Alternative 2) Read the entire page →
From page 81... ... Project Examples 81 Despite the lack of bicycle facilities on Cascade Avenue, it is already a frequently used route by bicyclists traveling between downtown and the university campus as it is the most direct route between those two origins-destinations. The posted speed on Cascade Avenue is 35 mph. Read the entire page →
From page 82... ... 82 Performance-Based Analysis of Geometric Design of Highways and Streets and existing motorists. The project will need to balance the impacts on existing automobile and transit service. Read the entire page →
From page 83... ... Project Examples 83 6.4.2.2 Potential Solutions Authors' Note: Section 5.3.2 provides useful information and considerations for how to develop potential solutions given the specific project context, intended project outcomes, performance measures, and influential geometric elements. The primary constraint and challenge in developing solutions for Cascade Avenue is serving the range of existing and desired road users within the existing right-of-way. Read the entire page →
From page 84... ... 84 Performance-Based Analysis of Geometric Design of Highways and Streets example, providing a transit-only lane has the ability to improve mobility and reliability for transit riders by reducing the average travel time along the corridor for transit riders. It also provides more predictable operating conditions for transit vehicles in peak traffic conditions. Read the entire page →
From page 85... ... Project Examples 85 • Alternative 4 -- Hybrid of Transit, Bicycle, and Pedestrian Alternatives: Four-lane undivided roadway with transit-only lanes, bicycle lanes, and a wider sidewalk. Alternative 4 is shown in Exhibit 6-18. Read the entire page →
From page 86... ... 86 Performance-Based Analysis of Geometric Design of Highways and Streets • Definition of transition areas on approach to intersections or major driveways where vehicle turning movements will occur; these conflict areas will need to be managed particularly within alternatives providing transit-only and/or bicycle lanes • Revisiting, confirmation, and possibly modification of intersection control, lane configurations, and/or signal timing (if a signal is present) to better align with the selected cross section For example, if Alternative 2, the transit-oriented cross section, is selected, the city may want to implement transit signal priority to help maintain consistent and reliable transit service along the corridor. Read the entire page →
From page 87... ... Project Examples 87 The project team faced several challenges in being able to quantitatively assess each alternative across the range of selected categories and associated performance measures. The primary challenge was the gap in existing research findings. Read the entire page →
From page 88... ... 88 Performance-Based Analysis of Geometric Design of Highways and Streets experience from specific road users' perspectives. Therefore, it is possible for the same alternative to produce a LOS C for bicyclists and LOS B for pedestrians. Read the entire page →
From page 89... ... Project Examples 89 vehicles moving in the opposite direction and provides a pedestrian refuge for pedestrian crossings at intersections and mid-block. These alternatives also include separate facilities designated for auto, transit, and bicycles. Read the entire page →
From page 90... ... 90 Performance-Based Analysis of Geometric Design of Highways and Streets Given these considerations purely based on performance evaluation results, the project team and broader stakeholders felt Alternatives 2 and 3 had performance characteristics best reflecting the attributes they desired for Cascade Avenue. The following section discusses the financial feasibility considerations. Read the entire page →
From page 91... ... Project Examples 91 Avenue that are not through residential areas. For those reasons, it was of high importance to the city to maintain a reasonable degree of mobility and reliability for motorists and transit, while better serving other modes. Read the entire page →
From page 92... ... 92 Performance-Based Analysis of Geometric Design of Highways and Streets metropolitan area to help preserve and limit the impact to the wetlands surrounding SR-4. The agency does recognize SR-4 is a critical alternate route to US-9 that should be maintained so it is able to continue to safely and reliably serve motorists and cyclists. Read the entire page →
From page 93... ... Project Examples 93 continue to use SR-4. The DOT is the primary agency stakeholder as it has jurisdiction over the roadway; the local FHWA environmental office is also a key governmental stakeholder within the project. Read the entire page →
From page 94... ... 94 Performance-Based Analysis of Geometric Design of Highways and Streets alternative and enables the DOT to address the basic question of whether investing in any of the alternatives provides sufficient value relative to how the existing condition is expected to perform. • Basic Alternative 2 -- Wide Shoulders: Increases shoulder widths to standard width for roadway functional classification and maintains similar sideslopes to the existing condition. Read the entire page →
From page 95... ... Project Examples 95 The key considerations influencing the selection of specific shoulder widths was the standard shoulder width dimension for a rural two-lane highway within the state. Another consideration was the approximate incremental safety effectiveness of wider shoulders, as documented in AASHTO's HSM (5) Read the entire page →
From page 96... ... 96 Performance-Based Analysis of Geometric Design of Highways and Streets Exhibit 6-22. Cross section of existing roadway. Read the entire page →
From page 97... ... Project Examples 97 physical size of the roadway prism footprint and the additional impervious area the alternative would add to account for the potentially negative impact of additional stormwater runoff into the adjacent wetlands. 6.5.3 Evaluation and Selection 6.5.3.1 Estimated Performance and Financial Feasibility Authors' Note: Sections 5.4 and 5.4.1 provide information and considerations regarding (1) Read the entire page →
From page 98... ... 98 Performance-Based Analysis of Geometric Design of Highways and Streets • Alternative 3 performs consistently in between Alternatives 2 and 3 with moderate results across the performance measures. Based on the performance results and assessment of the impact to the adjacent environmentally sensitive area, the DOT is considering Alternative 4 because of its safety performance, recoverable sideslopes to mitigate the probability of severe roadway departure crashes, and the no net gain in impervious area. Read the entire page →
From page 99... ... Project Examples 99 in impervious surface area. As a result, the DOT and project stakeholders did not want to oversimplify or omit performance measures they felt to be critical in selecting an alternative for SR-4. Read the entire page →
From page 100... ... 100 Performance-Based Analysis of Geometric Design of Highways and Streets evaluate the alternative solutions. This project example is first introduced within Sections 3.1.1 and 3.1.2 in the discussion regarding how to identify whom a project is serving and what is trying to be achieved. Read the entire page →
From page 101... ... Project Examples 101 accessibility, quality of service, and safety are the geometric performance categories of interest. We used Sections 4.4.1 (Accessibility) Read the entire page →
From page 102... ... 102 Performance-Based Analysis of Geometric Design of Highways and Streets 27th Avenue, the city will need to avoid, and demonstrate there is no, significant impact to the hillside from the 27th Avenue construction. If it is unable to demonstrate no significant impact, the city will need to produce an EIS. Read the entire page →
From page 103... ... Project Examples 103 following design parameters to explore because of their direct relationship to the previously mentioned performance measures: • Intersection geometry as it relates to being able to accommodate large vehicles (e.g., radius of curb returns) • Lane width • Bicycle facility presence and type (e.g., bicycle lanes) Read the entire page →
From page 104... ... 104 Performance-Based Analysis of Geometric Design of Highways and Streets Solution Development. In this project, the project team was challenged to consider a range of options for an alignment as well as cross-section characteristics to try to achieve the varied performance measures previously discussed. Read the entire page →
From page 105... ... Project Examples 105 nificant environmental impact. The potential connections to regional transportation facilities include the following: • US-33 -- A highway serving as a key transportation freight corridor reaching from coastal communities west of the industrial area to urban, suburban, and rural mountain communities east of the industrial area. Read the entire page →
From page 106... ... 106 Performance-Based Analysis of Geometric Design of Highways and Streets • Alternative 2 -- Freight with Bicycle Accommodations: Two-lane roadway with 12-ft-wide travel lanes and a 14-ft-wide two-way center left-turn lane (total three-lane cross section) Read the entire page →
From page 107... ... Project Examples 107 The exhibits show there are a few common elements across the alternative cross sections: • A two-way center turn lane to facilitate access to future industrial uses fronting 27th Avenue • Sidewalks to separate pedestrian activity and vehicle movement • One through travel lane in each direction, which was deemed sufficient given 27th Avenue will be primarily facilitating internal circulation 6.6.3 Evaluation and Selection 6.6.3.1 Estimated Performance and Financial Feasibility Authors' Note: Sections 5.4 and 5.4.1 provide information and considerations regarding (1) how to estimate the performance of project alternatives or specific geometric design decisions and (2) Read the entire page →
From page 108... ... 108 Performance-Based Analysis of Geometric Design of Highways and Streets employers from having to evaluate and/or seek environmental clearance to move into the newly zoned area. • Provides a connection to US-33 in two different locations. Read the entire page →
From page 109... ... Project Examples 109 As shown in Exhibit 6-34, each of the cross sections is estimated to have the same number of crashes per year even though across the alternatives there are changes in lane width, bicycle lane presence and width, and sidewalk width. The reason the expected crashes per year do not change across the alternatives is because the methodology in Chapter 12 of the HSM applicable to urban and suburban facilities is not able to quantify the safety effects of changes in lane width, presence or width of bicycle lanes, or the presence or width of sidewalks (5) Read the entire page →
From page 110... ... 110 Performance-Based Analysis of Geometric Design of Highways and Streets 6.6.3.2 Selected Alternative Authors' Note: Section 5.4.2 presents considerations with respect to selecting a preferred project alternative or determining the appropriate specific geometric design decisions (e.g., radius of a horizontal curve) Read the entire page →
From page 111... ... Project Examples 111 Over the last two decades, development from the urban and suburban communities in the west has gradually pushed further east. As a result, there has been a higher volume of cross-street traffic at several locations along US-6 in what was once a rural and remote area. Read the entire page →
From page 112... ... 112 Performance-Based Analysis of Geometric Design of Highways and Streets Section 3.1 provides guidance and anecdotal examples of how to identify whom the project is intended to serve and what the project is intended to achieve. Sections 3.2 and 3.3 describe the overarching relation ship and differences between defining project performance and geometric design performance. Read the entire page →
From page 113... ... Project Examples 113 existing two-way stop-controlled intersection to (1) traffic signal control, (2) Read the entire page →
From page 114... ... 114 Performance-Based Analysis of Geometric Design of Highways and Streets Interchange Form. The range of potential interchange forms appropriate for a given location are initially governed based on the type and function of the roadway facilities being connected by the interchange. Read the entire page →
From page 115... ... Project Examples 115 Interchange Form Alternatives. This subsection presents schematics of the three alternative interchange forms: • Diamond Interchange: Diamond interchange providing access to and from Stonebrook Road and US-6. Read the entire page →
From page 116... ... 116 Performance-Based Analysis of Geometric Design of Highways and Streets Stonebrook Road and eliminates the westbound left-turn movement from westbound US-6 onto southbound Stonebrook Road. Shown in Exhibit 6-39. Read the entire page →
From page 117... ... Project Examples 117 Road for constructing the on-/off-ramps for the new interchange. From a constructability perspective, that may not be sufficient space to keep the existing Stonebrook Road open to traffic throughout construction. Read the entire page →
From page 118... ... 118 Performance-Based Analysis of Geometric Design of Highways and Streets available and can be used to predict crash frequency and severity for different interchange and ramp terminal configurations. However, the final report for NCHRP Project 17-45 (14) Read the entire page →
From page 119... ... Project Examples 119 ramps within the two-quadrant Parclo A and Parclo B forms is associated with higher expected crashes. Delay for Stonebrook Road was not estimated for each of the interchange forms because that performance metric is directly related to the ramp terminal intersection control. Read the entire page →
From page 120... ... 120 Performance-Based Analysis of Geometric Design of Highways and Streets their right-of-way impacts would be constrained to fewer quadrants of the interchange. The circular ramps for the two-quadrant Parclo A and Parclo B ramps also create some opportunities for on-site stormwater management treatments that are reflected as potential cost savings relative to the diamond interchange. Read the entire page →
From page 121... ... Project Examples 121 to the new suburban residential development and shopping center. The DOT and county held several meetings with the new residents within the development, the developer in the process of selling the remaining homes, and the businesses within the new shopping center. Read the entire page →
From page 122... ... Abbreviations and acronyms used without deﬁnitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) Read the entire page →

From page 61...

... 61 C H A P T E R 6 6.1 Introduction These project examples are intended to help users apply the concepts, models, and performance evaluation framework element presented in Chapters 1 through 5. The project examples are based on a variety of specific projects, amalgams of projects, or project considerations that can be commonly found in practice.