Practices for Adding Bicycle and Pedestrian Access on Existing Vehicle Bridges (2023)

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7   Review of Literature and Practice This chapter discusses the current status of identification, evaluation, and prioritization of bridge retrofit projects to incorporate bicycle and pedestrian accommodations, factors to deter- mine accommodation strategies, and performance measures to monitor the benefits associated with these projects. This discussion is based on two types of analyses. The first type was the review of academic literature, guidebooks, reports, and technical resources as identified through the Transportation Research Information Database, U.S. DOT, various internet search engines, and professional associations. The second type included the creation of an inventory of state DOT guidelines that addresses pedestrian and bicycle accommodations. Project Selection/Prioritization Many bridges, although originally designed only for motorized vehicles, can provide connections for local, active road users as well. Alternatives that require the construction of standalone structures (e.g., parallel pedestrian bridge) can be difficult to justify due to funding and management chal- lenges (Nance 2012). Retrofitting is a more feasible way to extend the life of a bridge while ensuring adequate accommodations are in place. Typical conditions that constitute a retrofit include: • The bridge is old and has undergone substantial degradation. • The bridge has a surge in traffic volume. • The bridge has a unique feature that limits its functionality (e.g., a drawbridge to accommo- date canal vessels). • The bridge is being used by bicyclists and pedestrians for essential services and employment. • The general security of the area needs to be improved for pedestrians. • Crime in the area deters pedestrian and bicyclist crossings. • The bridge exacerbates the existing equity issues in its area. Bridges are also often selected to be retrofitted to address the gap in bicycle-pedestrian con- nectivity in various iterations of transportation plans—notably the complete street initiative that many state DOTs are adopting (Hourdos et al. 2017). Advocacy groups also help set such infra- structure projects in motion by stating equity and safety performance concerns (Nance 2012). Opportunities for transportation in anything but a passenger vehicle are limited in areas with low population densities, segregated land uses, and a lack of multimodal infrastructure. Three factors are imperative for incorporating active transportation modes into the capital program- ming process: • Dedicated funding sources. • Advocates who fully understand the programming schedule. • Mechanisms to assess the benefits of such investments with traditional highway investments (Miller and Ohlms 2014). C H A P T E R 2

8 Practices for Adding Bicycle and Pedestrian Access on Existing Vehicle Bridges Strategies to Accommodate Pedestrians and Bicyclists When bridge owners develop funding proposals to incorporate active transportation accommodations, extra care must be taken during project scoping to identify feasible alter- natives and develop accurate cost estimates. To alleviate project scoping and cost-estimation challenges, the owner agencies must have access to a methodology and a tool to evaluate a site for the best possible alternatives and to develop corresponding cost estimates (Attanayake et al. 2015). Two distinct strategies to provide bicycle and pedestrian accommodations include bridge retro fit alternatives and new bridge construction. The retrofit alternative expands or adds missing bicycle and pedestrian accommodations on the existing bridge as opposed to constructing a new separate bridge for exclusive use by active transportation users (Nance 2012). The new bridge alternative is usually much more costly and difficult to implement due to geometry and right-of-way limitations. Attanayake et al. (2015) identified two broad categories of alternatives to accommodate active transportation users on bridges. The first category is to accommodate active transportation users within the bridge (listed 1–5). The second category is to accommodate active transportation users outside the bridge (listed 6–8): 1. Shared-use path and shared lanes with no special provisions. 2. Sidewalk and wider shared lanes. 3. Sidewalk and bike lanes. 4. Shared-use path and wider shared lanes. 5. Shared-use path and bike lanes. 6. Cantilevered structure for active transportation users. 7. Hanging structure for active transportation users. 8. Free-standing structure for active transportation users. Alternatives 6–8 are chosen when the geometry of a bridge does not allow for pedestrian and bicycle accommodations within the bridge. Additionally, alternatives 6 and 7 require a bridge condition assessment and a detailed analysis of the existing structure (Attanayake et al. 2015). In the study, the authors compare costs associated with different alternatives, find that there is not much difference among these alternatives, and suggest the alternatives that provide the greatest level of user comfort. Interventions can also be categorized by scale and complexity, such as temporary measures that may be less costly (Nance 2012). Typical countermeasures to improve access for active trans- portation users include lane re-striping, signage, lighting improvements, bridge railing renewal, storm drain grate renewal, and debris pickup (Nance 2012). Factors Affecting the Selection of Strategies In many cases, bridges cross different jurisdictions and therefore have different owners, which means changes require the involvement of multiple agencies. This factor could limit or alter the option of alternatives to retrofit a bridge, both physically and administratively (Nance 2012). The projected demand and user volume are also tied to the demographics, concentration of jobs, and amenities around a bridge site and what the bridge connects (Nance 2012). Environmental impacts are also a factor affecting the selection of strategies. For example, the construction of separate structures to accommodate active transportation users (Dover/Kent County MPO 2012) could be less suitable due to concerns for the environment (Nance 2012). Potential environmental concerns include:

Review of Literature and Practice 9 • Habitats of threatened or endangered species in the vicinity of the site. • Air quality impact from the construction. • Noise pollution from construction. • Bank erosion of the waterway (Multnomah County 2010, Nance 2012). Nance (2012) stresses that retrofit projects do not always pose a direct environmental threat. When there is a threat, an enhancement to nearby natural habitats can provide mitigation oppor- tunities to offset the impact of construction (Nance 2012). Aside from effects on the environment, a project to accommodate pedestrians and bicyclists on bridges can hamper the fulfillment of the transportation agency’s goals, such as those regarding motor vehicle travel time and delay. Alternatives that address bicycle and pedestrian access need to further the goals of the city or region to be competitive (Nance 2012). The method developed by Attanayake et al. (2015) evaluates a bridge site and identifies the most suitable and cost-effective alternative to provide pedestrian and bicycle access across an existing bridge. As Figure 3 shows, the method incorporates bridge geometric parameters, site characteristics, safe passage alternatives, and specification/guideline requirements and is based on AASHTO specifications as well as relevant guidelines and information from the Americans Source: Attanayake et al. (2015). Figure 3. Method to consider pedestrian and bicyclist access on bridges.

10 Practices for Adding Bicycle and Pedestrian Access on Existing Vehicle Bridges with Disabilities Act (ADA). The process starts with identifying whether the bridge is considered for replacement. If it is, planners must provide facilities for active transportation users. If it is not, planners evaluate how to add pedestrian and bicycle accommodations across the existing bridge. Site information such as road classification, traffic speed, average daily traffic volume, lane width, and number of lanes is used to aid decisions. Guidelines such as AASHTO are reviewed for iden- tifying minimum space for active travelers. The alternatives to accommodate active transporta- tion users within the bridge are considered and selected. If the available space is greater than the minimum space required, alternatives within the bridge are evaluated. If available space is not greater than the minimum space required, the alternatives outside of the bridge are evaluated. Analysis in this method is automated using Excel/Visual Basic. Additional AASHTO and ADA guidelines for railings, ground surface, and surface elevations related to pedestrian and bicyclist facilities are included. These horizontal design criteria and specifications can be used to evaluate accommodation alternatives for a given bridge configuration (Attanayake et al. 2015). After the analysis, if accommodating pedestrians and bicyclists is not suggested, the author notes that non-compliant design exceptions can be submitted for the approval of the chief engineer of the respective highway department (Attanayake et al. 2015). Performance Measurement Attanayake et al. (2015) obtained 10 case examples from various state DOTs with an over- view of each bridge, the site conditions of each bridge, and the identification of alternatives employed to accommodate active transportation users. Each review also included the diagram of the bridge’s cross section and detailed graphics of the accommodations. These bridges include: • Route 10 bridge over the St. Jones River, Delaware. • Ashley River bridge in Charleston, South Carolina. • Novi Road bridge over I-96, Michigan. • Huron Street bridge over I-94, Michigan. • M-43 bridge over US-13, Michigan. • Mosel Avenue bridge over the Kalamazoo River, Michigan. • US-131 underpass for the Kalamazoo River Valley Trail, Michigan. • Meadowbrook Road bridge over I-96, Michigan. • Scio Road bridge over I-94, Michigan. • Ann Arbor-Saline Road bridge over I-94, Michigan. In the review, Cohn and Sperling (2016) identified that providing bicycle and pedestrian access to bridges during a bridge rehabilitation project could facilitate active travel network connectivity and improve safety performance. It also could enhance access for active travel users to essential destinations, increase the level of physical activity, decrease greenhouse gas emissions, and promote social equity. Adding a bicycle or pedestrian facility during a bridge rehabilitation project is more cost-effective than providing the same facility on a completed project or constructing a standalone bicycle and pedestrian bridge. Attanayake et al. (2015) implemented the aforementioned analysis process on three existing bridges without pedestrian and bicycle accommodations to demonstrate the method. Cost esti- mations were prepared using data from past project documents. Input data provided by MDOT and local engineering firms were also included for every alternative. The three existing bridges include the following: • 9th Street bridge over I-94, Michigan. • 44th Street bridge over I-196, Michigan. • 102nd Avenue bridge over US-131, Michigan.

Review of Literature and Practice 11 Three critical limitations of this analysis process were discovered: • The current version of the program is limited to providing alternatives within the bridge. • The alternative analysis is solely based on quantitative data. Qualitative data could complement the analysis and provide a more comprehensive evaluation. • Only the direct cost of the specific alternative is presented (Attanayake et al. 2015). Different types of bicycle facilities and multimodal designs are implemented for safe, effi- cient infrastructure for cyclists, yet comparatively few of these designs have been evaluated. County and municipal engineers have identified gaps in the technical guidelines associated with the lack of evaluation (Hourdos et al. 2017). To assess and evaluate a potential bridge project, Hourdos et al. (2017) identified two questions that should be answered by transporta- tion agencies: 1. What effects do the construction of a certain intervention of the retrofit project have on the choice of riding location by bicyclists? 2. Does the construction of an intervention affect the frequency or type of interactions between active transportation users and motor vehicles? (Hourdos et al. 2017) Hourdos et al. (2017) evaluated the practice of constructing accommodations for bicyclists crossing the Veteran’s Memorial Bridge over the Minnesota River. The project involved narrowing the motor vehicle travel lanes and widening the existing sidewalks to make them into shared- use paths. Pre-construction bicycle facilities consisted of on-street 6-foot shoulder/bike lanes (i.e., a shoulder with a fog line adjacent to travel lanes) running eastbound and westbound. The post-construction cross section included 3-foot shoulders with no marked bicycle facility and a new shared-use path on both sides of the roadway. To evaluate the safety performance of the new bicycle/pedestrian facilities, they used manual reduction of video recordings categorizing the results of the defined criteria and assessed lane choices by bicyclists as well as changes in bicyclist-driver interactions following construction. They discovered that by changing shoulder/ bike lanes into the shared-use path (i.e., merged sidewalk and bike lane plus minimal shoulder), the following actions occurred: • Cyclists shifted from the shoulder to fully utilize the shared-use path. • Cyclist-pedestrian conflicts decreased, because bicyclists often rode on the sidewalk in the pre-construction conditions conflicting with pedestrians. After the shared-use path was installed, the two modes had fewer conflicts. • A high proportion of vehicle drivers increased the distance between their motor vehicles and the bicyclists when overtaking cyclists on the shoulder. • Bicycle traffic on the road decreased. While increasing active transportation users is usually one of the goals of bridge retrofit projects (Nance 2012), it is difficult to evaluate quantitative metrics in short-term observations, since users might need extra time to learn about and use the newly implemented facilities. However, the immediate change in user behaviors, such as providing increased passing dis- tance, can show that bridge retrofits increase safety performance on existing bridges (Hourdos et al. 2017). In the future development of retrofit projects, it will be appropriate to evaluate operational and demand impacts such as changes in vehicle delay and bicycle frequency. This information will be needed to calculate the cost to accommodate bicyclists (Miller and Ohlms 2014). On a national level, a better understanding of the safety performance of treatments is needed. One example would be studying the impact of lane widths on same-direction motor vehicle sideswipe crashes, given the variation in geometry and operational characteristics (Miller and Ohlms 2014).

12 Practices for Adding Bicycle and Pedestrian Access on Existing Vehicle Bridges Guidance Documents Various guides have been developed to inform the practices of providing a safe passage for active transportation and motor vehicle facilities. The following list includes some of these guides: • AASHTO Guide for the Development of Bicycle Facilities (2012). • AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities (2021). • AASHTO Guide on Geometric Design of Transit Facilities on Highways and Streets (2014). • AASHTO A Guide on Achieving Flexibility in Highway Design (2004). • AASHTO A Policy on Design Standards, Interstate System (“AASHTO Interstate”) (2016). • AASHTO A Policy on Geometric Design of Highways and Streets (“Green Book”) (2018). • Federal Highway Administration (FHWA) Achieving Multimodal Networks (2016a). • FHWA Small Town and Rural Multimodal Networks (2016b). • FHWA Update to Controlling Criteria (2022). • National Association of City Transportation Officials (NACTO) Urban Street Design Guide (2013). • NACTO Urban Bikeway Design Guide (2014). • NACTO Transit Street Design Guide (2016). • Massachusetts Highway Department. Project Development and Design Guide (2006). • MassDOT. Separated Bike Lane Planning and Design Guide (2015). In addition, several state DOTs have adopted design guidelines for accommodating pedestri- ans and bicyclists when retrofitting existing bridges. The table in Appendix D lists takeaways in select state DOT guides and manuals. Summary of the Literature Review Findings Retrofitting bridges to include bicycle and pedestrian facilities is a relatively new practice of state DOTs. While many states adopted transportation plans focusing on multimodal planning and Complete Streets projects a decade or two ago, providing access to active transportation users on bridges is a more recent activity, as state DOTs take the opportunity to improve con- nectivity and create a more balanced multimodal transportation system (Hourdos et al. 2017). The benefits that bicycle and pedestrian accommodations on bridges provide include con- nectivity and safety (Hourdos et al. 2017) as well as accessibility, health, sustainability, cost savings, and social equity (Nance 2012, Cohn and Sperling 2016). However, it can be challenging to incorporate non-automobile modes into the capital programming process without dedicated funding, advocates, and the ability to assess the benefits of providing accommodations (Miller and Ohlms 2014). In terms of processes that are suggested for the selection of bicycle and pedes- trian accommodations in bridge retrofit projects, it is crucial to take the following actions: 1. Evaluate the safety aspects of all potential pedestrian and bicyclist passage alternatives. 2. Perform traffic safety studies to determine the number of pedestrian and bicyclist conflict points and develop suggestions to improve safety performance. 3. Evaluate available live-load models and analyze procedures to develop a unified approach in the final selection of alternatives (Attanayake et al. 2015). Federal guidelines may be helpful to states and cities looking for support when making decisions during the planning, design, and construction phases of bridge retrofit projects. As discussed in this literature review, state DOTs have been working to include accommodations for active transporta- tion users in their bridge retrofit projects in recent years.