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Gap-Filling Strategy

Aerial view photography of bicyclist | Photo courtesy Getty Images

RTC’s TrailNation™ Playbook curates case studies, best practices and tools to accelerate trail network development nationwide. Explore each section for lessons learned that can support trail planners, municipalities, states and regions working to advance trail network projects.

Project Vision | Coalition BuildingMapping and Analytics | Gap-Filling Strategy | Investment Strategy | Engagement

TrailNation Playbook Gap-Filling Strategy logo by RTC

Converting trail network gaps—whether identified planned trails or more conceptual desired connections—into well-supported projects that attract investment will require strategies that leverage political, natural and economic capital. Once the trail network is defined, a more detailed assessment of the gaps will yield project priorities that can be harnessed to accelerate trail network completion and build momentum for the overall project vision. This process leverages expertise and resources among coalition partners, and builds upon mapping and analytics by taking a network-based approach to trail planning and development.

A corridor gap in a trail network vision is the physical space between two or more existing trails. It is the absence of a trail or other accessible connecting corridor. Whether the gap is many miles or just a short distance, the result is the same. The absence of completed trail prevents the trail network from being fully connected and creates a barrier that discourages use of the network as a bicycling and walking route to everyday destinations because it is inconvenient, unsafe or both. These trail network gaps can create real problems for trail planners and trail users, but they also represent opportunity to address challenges within the neighborhoods connected by the trail and provide new, equitable access to active transportation and spaces to be physically active.

Corridor gaps present challenges to everyone who uses trails for recreation, commuting, health and exercise. When a trail gap exists in a network, a trail segment may terminate in a location where there are no longer separated bicycle and pedestrian facilities—like trails, separated bicycle lanes or sidewalks—putting bicyclists and pedestrians in real physical danger. Trail network and wayfinding signage can also be difficult to navigate in gap locations. This can also mean that certain destinations are not accessible to people using active transportation or that the trail network is not accessible to those living and working within a gap segment. Regionally these gaps present challenges to interconnectivity between economies, transportation systems and other assets that can contribute to regional economic advantage.

There are many types of bicycle and pedestrian facilities that make up regional trail networks, but many envision an interconnected system of shared-use paths, or multiuse trails, separated from motor vehicles. Trail, bicycle and pedestrian design guidance and standards are important resources in determining how gaps might be filled and which facility types make feasible connections.

Trail network gaps are established through the mapping process and may be identified as a planned trail, a conceptual route or an area where no route is identified but a connection from one trail to another is desired. Some trail networks focus on connecting off-road shared-use paths like the Capital Trails Coalition in Washington, D.C., while others may use a combination of facility types to connect the network like the Caracara Trails in the Lower Rio Grande Valley in Texas.

Types of Trail Network Connections

There are many types of trail connections that can be considered in the gap-filling process. Consider what existing linear corridors or rights-of-way might be feasible for trail development and, where necessary, what on-street bicycle facilities may help bridge gaps in the network.

Rail-trails are multipurpose public paths created from former railroad corridors. There are nearly 25,000 miles of rail-trails across the United States, and many existing rail-trails are considered “spines” of regional trail networks.

Rails-with-trails are shared-use, or multiuse, paths adjacent to or within an active railroad corridor. This growing trend in trail development co-locates a trail with passenger, freight, transit, excursion, short line or other type of active railroad to maximize the corridor’s unique character as an uninterrupted linear connection between points.

Utility corridors may provide opportunity for trail development along the same uninterrupted linear corridors that water, gas and electric companies use to traverse the landscape with minimal impact on adjacent land uses, thus reducing the amount of property negotiations needed to build a trail across a distance. Locating trails on utility corridors requires significant relationship building and planning but pays off when trail development benefits the trail user, trail manager and utility company.

Greenways are linear spaces with a focus on connecting people and places, often featuring paths, amenities like playgrounds and pocket parks, and other green features. Many rail-trails and other shared-use paths can be considered greenways.

Cycle tracks are exclusive bike facilities that combine the user experience of a separated path with the on-street infrastructure of a conventional bike lane. Where on-street connections are the only options for trail network connectivity, cycle tracks provide a desired user experience.  

A collaborative and systematic mapping process will provide a solid foundation for performing analytics that guide project prioritization and gap filling and support equitable trail development planning practices. After the gaps are identified, coalitions often begin to assess how these planned connections should be prioritized to focus their planning and advocacy efforts. Many different factors may determine project priorities, including existing equity, economic health and environmental plans of individual jurisdictions within the trail network; available budgets or access to funding; right-of-way access and ownership; political will and support; and more.  

The Capital Trails Coalition in the Washington, D.C., metro area used an analytical process to prioritize new trail projects based on threefold criteria. The criteria required that the trail network intersect the boundary of high-population-density areas with low-income Communities of Color that are also designated Metropolitan Washington Council of Governments (MWCG) Activity Centers, where MWCG recommends that growth be concentrated. The coalition also asked each member jurisdiction to submit its own top trail development priorities. The coalition then overlaid the two lists. This process yielded 40 featured trail projects, which were organized based on their priority status—stated jurisdictional priorities, priorities that emerged through the mapping and analytics stage, or both.


In southeast Wisconsin, Rails-to-Trails Conservancy (RTC) conducted a study on behalf of the Route of the Badger coalition to understand access to trails and bicycle connectivity throughout the city of Milwaukee. The study found that neighborhoods experiencing inequality in Milwaukee—those where a concentration of the population live under the poverty line, are unemployed, do not have a high school degree, do not own a vehicle, and are either African American or Latino—disproportionately lack access to biking and walking facilities.

Using BikeAble™, RTC’s GIS-modeling platform that analyzes the bicycle connectivity of a community to determine the best low-stress route for bicycling between a set of user-specified origins and destinations, the study demonstrated that the completion of two key Milwaukee corridors that are part of the Route of the Badger network would create new trail access for more than 200,000 people in the city. This type of analysis provides direction to trail planners and advocates seeking to use equitable decision-making tools for project prioritization.


Another example of project prioritization that is essential to defining a gap-filling strategy is the Central Ohio Greenways Regional Trail Vision Prioritization. Setting the stage for a strategic trail implementation phase, Central Ohio Greenways analyzed how segments of its proposed trail network vision in Franklin County support regional priorities around land use, transportation and recreation. The Franklin County Engineer’s Office, the City of Columbus Department of Public Service and the Mid-Ohio Regional Planning Commission developed criteria related to connectivity, health, the environment, social equity and economic development to inform the prioritization analysis of the network, ranking segments of the proposed vision that have the potential to impact the region most dramatically.


Trail network gaps are identified through the mapping process, which should include a thorough plan review, stakeholder input and ground-truthing. Visiting identified gaps in person to verify mapping data can also provide opportunities to explore existing conditions and connections. Early site visits give trail planners and advocates the perspective of what the trail may look and feel like, which can also be essential in public engagement efforts. Together with equitable trail planning practices, the following steps may occur after gaps are identified, and any project prioritization efforts or analyses may inform how and when trail planning occurs.

Strategies for Maximizing Planning

During the planning phase, consider these strategies to bring maximum benefit to the project.

  • Explore opportunities for trail connections with stakeholders and members of the coalition. Use site visits to evaluate feasibility together and to strengthen partnerships and community needs.
  • Conduct SWOT (Strengths, Weaknesses, Opportunities and Threats) analyses to more thoroughly understand opportunities and risks in the landscape and communities of each corridor option.
  • Build awareness and political will to develop and implement trail plans. Feasibility studies are a good first step to raise public awareness of the opportunity and engage stakeholders broadly in solutions-oriented problem solving that can come from filling in gaps in the trail network.
  • Working with stakeholders and champions, advance the gap-filling concept in the early planning stages of the process using feasibility studies and preliminary concept development to engage the community. This is a good time to engage and even develop community-led processes to define how a trail can best meet local residents’ needs.
  • Work with local leaders and local governments to make sure the gap-filling strategy is included in official planning documents such as master plans, vision plans, community development plans and regional blueprints. This endorsement can accelerate the trail development process.

Examples of effective trail-network planning efforts can be seen across RTC’s TrailNationTM projects.

View of the 30th Street corridor in Milwaukee, looking south from the North Avenue Bridge (2020) | Photo courtesy RTC
View of the 30th Street corridor in Milwaukee, looking south from the North Avenue Bridge (2020) | Photo courtesy RTC


30th Street Corridor Shared-Use Trail Preliminary Feasibility Study

This study analyzes the feasibility of a shared-use trail along Milwaukee’s 30th Street rail corridor as part of the Route of the Badger initiative in southeast Wisconsin. The study answers important technical questions that will likely arise as project development continues, while also setting the stage for an engagement process to define how a trail could best meet community needs. Next steps include working with neighborhood leadership to craft and implement an equitable development plan on the intersectional issues at play in the neighborhoods surrounding the 30th Street corridor. The process will ensure that any future shared-use trail project is a driver of far-reaching, sustaining benefits for current residents.

Western Reserve Greenway | Photo by TrailLink user vicky1960
Western Reserve Greenway | Photo by TrailLink user vicky1960


Connecting Ashtabula to Pittsburgh by TrailConnecting Cleveland to Pittsburgh by Trail and Connecting Parkersburg to Pittsburgh by Rail-Trail

These feasibility studies examine key gaps within three major corridors of the Industrial Heartland Trails network, which will one day connect across 1,500 miles between Pennsylvania, West Virginia, Ohio and New York. The studies serve as blueprints for gap filling by identifying funding sources, partnership opportunities, and the planning and municipal processes required to complete the undeveloped gaps. Complementary economic impact studies were produced to demonstrate the annual return on investment from two existing trails—Mon River Trail System and Ohio & Erie Canal Towpath Trail—within these corridors, and serve as a tool to demonstrate the untapped economic potential of the trail networks when complete.

Gurney Street Trail Ribbon Cutting (2018) | Photo courtesy RTC
Gurney Street Trail Ribbon Cutting (2018) | Photo courtesy RTC


Richmond Industrial Trail Feasibility Study

Motivated by a major railroad corridor cleanup effort, the City of Philadelphia created an opening for trail development on a 1.87-mile corridor that would provide new access to the regional 800-mile trail network, the Circuit Trails. In 2018, RTC extended the exploration of a conceptual trail and completed an initial study of the corridor that analyzed previous planning efforts and transportation corridors within this focus area, engaged community-level stakeholders, and ultimately provided a series of recommendations for advancing this important trail.


Visioningcoalition building, and mapping and analytics will help trail planners and partners identify and prioritize gaps, while engagement and investment strategies will leverage resources to fill in the gaps. In particular, many of the strategies and practices developed and implemented during visioning and coalition building also apply to gap filling. For example, power-mapping exercises can be useful in identifying stakeholders along a planned segment of the trail network, determining local champions, and building a coalition of partners who will advocate and focus on gap filling at the local level.

Within the larger coalition, working groups could be developed to specifically address trail network gaps or to focus on individual projects. These action teams can report back to and use the advocacy leverage of the larger coalition to advance planning, outreach, design and construction of the trail to complete priority projects and fill in trail network gaps.

While public investment in trail networks helps demonstrate a community’s commitment to the vision, private sector investment can expedite a gap-filling strategy. Once a gap is identified as a priority project in an official plan, it may become easier to engage the philanthropic or private sectors in advancing trail design or construction to assist the public sector in completing the trail network. Local or national philanthropic organizations may see the opportunity to assist the public trail-building entity as aligning with their public service-oriented missions.

In communities across the country, foundations have supported preliminary design, planning or outreach work. This philanthropically funded preliminary work can then be used by local municipalities as a match to become eligible for state or federal dollars essential to advancing the trail design or construction. In other cases, the philanthropies have funded trail network construction directly. This is only possible when there is a clear strategy that articulates the public benefit, commitment from the municipality and community need, all of which can be identified through a SWOT analysis.   

A SWOT analysis is a powerful tool for gap filling and provides an opportunity for input among a diverse coalition. In some cases, a thorough SWOT analysis of landowners in a corridor gap may reveal a large landowner such as a university, anchor institution or utility with an incentive to be located on a trail. This can lead to land donations, easements, trail maintenance support or even assistance building the trail to connect the network.

Other private sector partners to consider are property developers and economic development professionals along a corridor gap. If ground is being broken on a brownfield or greenfield for a housing, commercial, business or institutional development, talk with the developers to understand their goals. Find out if bringing a trail into their plans brings mutual benefit to the development and the connection to the broader community. Developers and real estate professionals may understand the inherent value in having their properties accessible by yet another mode of transportation and will recognize the benefits of being connected to a trail network, like helping offset project costs for the trail network by building segments of the trail as part of their site development.

Maintaining relationships with community groups, community development corporations, trade groups, chambers of commerce, and public and private economic development professionals as well as the design community (architects, planners, landscape architecture firms) is also essential to identifying potential private sector partners and potential future investment opportunities.

Foundations Advancing Regional Trail Network Development

The William Penn Foundation was an early supporter of efforts to develop the Circuit Trails network in greater Philadelphia. The foundation has invested more than $33 million in capital funding to Circuit Trails through the Delaware Valley Regional Planning Commission since 2010 and continues to help fuel its success. The foundation recognizes “that trails provide important co-benefits, like economic growth, job creation, human health, accessible transportation routes and an improved climate.”

The Valley Baptist Legacy Foundation has invested millions of dollars in trail planning, design and construction as part of its focus on community health and wellness in Texas’ Lower Rio Grande Valley. Through the foundation’s support of a regional active transportation and tourism plan, Caracara Trails was formed to realize the vision for a 428-mile trail network that will link the rich natural, cultural and historical resources the area is known for—creating a unified regional identity for outdoor tourism, promoting healthier lifestyles and generating a new sense of community pride for everyone who lives there.


Project Vision | Coalition BuildingMapping and Analytics | Gap-Filling Strategy | Investment Strategy | Engagement | Engagement

Each element of the playbook to build trail networks is integrated. While the process is not linear, each aspect plays an important role. When developing a process and strategy for gap filling, consider these points: