Draft Indicator for Future Blueprint Update: Landscapes - Greenways & Trails

Greenways and trails
This layer is a draft landscapes indicator for use in a future version of the South Atlantic and Southeast Blueprints. It is an index that evaluates the natural condition and connected length of greenways and trails.

Reason for Selection
This indicator captures the recreational value and opportunities to connect with nature provided by greenways and trails. Greenways and trails provide many well-established social and economic benefits (ITRE 2018).

Supplemental Legend Info

Monitoring Approach
Locations of greenways and trails are regularly updated through the open source database OpenStreetMap. Data on condition are updated every 5 years through the National Land Cover Database (NLCD).

Input Data
– OpenStreetMap data “roads” layer (accessed 4/9/2018): A line from this dataset is considered a potential greenway/trail if the value in the “fclass” attribute is either bridleway, cycleway, footway, or path.
– National Land Cover Database 2011 (NLCD 2011): Percent developed imperviousness

Mapping Steps
The greenways and trails indicator score reflects both the natural condition and connected length of the greenway/trail.

Natural condition
Natural condition is based on the amount of impervious surface surrounding the greenway/trail. Since perceptions of a greenway’s “naturalness” are influenced both by the immediate surroundings adjacent to the path, and the greater viewshed, natural condition was calculated by averaging two measurements: local impervious and nearby impervious. Local impervious is defined as the percent impervious surface of the 30 meter pixel that intersects the trail. Nearby impervious is defined as the average impervious surface within a 300-m radius circle surrounding the path (note: along that 300 m stretch of trail, we only count the impervious surface within a 45 m buffer on either side of the trail, since pixels nearer the trail have a bigger impact on the greenway/trail experience). The natural classes are defined as follows:

3: Mostly natural: average of local and nearby impervious is <=1%
2: Partly natural: average of local and nearby impervious is >1 and <10%
1: Developed: average of local and nearby impervious is >=10%

Connected length
The connected length of the path is calculated using the entire extent of the potential greenways/trails dataset. Length thresholds were defined by typical lengths of three common recreational greenway activities: walking, running, and biking. The 40 km threshold for biking was based on the standard triathlon biking segment of 40 km (~25 mi). Because a 5K is the most common road race distance, the running threshold was set at 5 km (~3.1 mi) (Running USA 2017). The 1.9 km (1.2 mi) walking threshold was based on the average walking trip on a summer day (U.S. DOT 2002).

Final scores
As a final step, if the potential greenway/trail did not have a value in the “name” field, it was considered a sidewalk and given a value of 1 to separate sidewalks from what most people think of as a trail or greenway. If a pixel did not intersect a potential greenway/trail, it was coded with a value of 0. This is consistent with the use of the value 0 in other indicators used in the Blueprint. Final indicator values were assigned as follows:

7: Mostly natural and connected for >40 km
6: Mostly natural and connected for 5-40 km or partly natural and connected for >40 km
5: Mostly natural and connected for 5-1.9 km, partly natural and connected for 5-40 km, or developed and >40 km
4: Mostly natural and connected for <1.9 km, partly natural and connected for 1.9-5 km, or developed and connected for 5-40 km
3: Partly natural and connected for <1.9 km or developed and connected for 1.9-5 km
2: Developed and connected for <1.9 km
1: Sidewalk or other path
0: Not a greenway, trail, sidewalk, or other path

Defining the Spatial Extent of Ecosystems
Landscapes and waterscapes indicators were defined as features that applied across all terrestrial and aquatic ecosystems and no refined extent was needed.

Known Issues
– Greenway length is sometimes underestimated when connections route under bridges or along abandoned dirt roads. Most of these issues have been fixed in the region from Southeast Virginia to North Florida, but are likely more prevalent in other areas of the South where there’s been less actively testing and improvement.
– Greenway segments that are not named in OpenStreetMap are scored too low. The name attribute is currently used to separate greenways and trails from sidewalks.
Most of these issues have been fixed in the region from SE Virginia to North Florida, but are likely more prevalent in other areas of the South where there’s been less actively testing and improvement.
– Sidewalks that are not greenways and trails, but are named in OpenStreetMap, may be mistakenly included as greenways and trails. The name attribute is currently used to separate greenways and trails from sidewalks. Most of these issues have been fixed in the region from SE Virginia to North Florida but are likely more prevalent in other areas of the South where there’s been less actively testing and improvement.
– When calculating nearby impervious for one greenway, and there’s another greenway within 300 m, impervious surface from the different but overlapping greenway buffer area is also used to compute natural condition. This is an unintended issue with the analysis methods. Investigation into potential fixes is ongoing.– The indicator doesn’t currently include areas where future greenways are planned.

Indicator Overview
The South Atlantic ecosystem indicators serve as the South Atlantic LCC’s metrics of success and drive the identification of priority areas for shared action in the Conservation Blueprint. To learn more about the indicators and how they are being used, please visit the indicator page. Check out the Blueprint page for more information on the development of the Blueprint, a living spatial plan to conserve our natural and cultural resources.

Literature Cited
American Planning Association. 2018. Unpublished draft report: Using the South Atlantic Conservation Blueprint to Improve Integration between the Natural and Built Environments.

Institute for Transportation Research and Education (ITRE) & Alta Planning and Design. February 2018. Evaluating the Economic Impact of Shared Use Paths in North Carolina: 2015-2017 Final Report. https://itre.ncsu.edu/wp-content/uploads/2018/03/NCDOT-2015-44_SUP-Project_Final-Report_optimized.pdf

Running USA. 23 March 2017. U.S. Road Race Trends. Road race finisher total experiences slight year-over-year decline in 2016. https://www.runningusa.org/2017-us-road-race-trends

U.S. Department of Transportation. National Highway Traffic Safety Administration and the Bureau of Transportation Statistics. 2002. National Survey of Pedestrian & Bicyclist Attitudes and Behaviors: Highlights Report. https://www.bts.gov/sites/bts.dot.gov/files/docs/browse-statistical-products-and-data/bts-publications/archive/203331/entire-1.pdf

Xian, G., Homer, C., Dewitz, J., Fry, J., Hossain, N., and Wickham, J., 2011. The change of impervious surface area between 2001 and 2006 in the conterminous United States. Photogrammetric Engineering and Remote Sensing, Vol. 77(8): 758-762.