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Publication Number: FHWA-RD-98-166
Date: July 1999
Guidebook on Methods to Estimate Non-Motorized Travel: Supporting Documentation
2.14 Pedestrian Potential and Deficiency Indices
Descriptive Criteria: What is It?
Authors and Development Dates:
City of Portland (1994)
The city of Portland, OR has developed two indices to help prioritize proposed pedestrian projects: the Pedestrian Potential Index and the Deficiency Index. The Pedestrian Potential Index identifies locations with high potential for pedestrian trip-making. The Deficiency Index identifies areas in which the quality of existing pedestrian facilities is low. The two indices are used in combination to identify projects in areas of high-demand potential and with significant existing deficiencies.
Pedestrian Potential Index - The Pedestrian Potential Index uses three main factors:
1. Policy factors that deem certain areas (i.e., urban activity centers) as critical for pedestrians.
2. Proximity factors that identify whether the segment is close to pedestrian generators such as schools, parks, transit, or neighborhood shopping.
3. Pedestrian potential factors that describe the likelihood of walking based on five environmental factors, namely, mixed use/density, proximity to destinations, street connectivity and continuity characteristics, average parcel size, and slope. The factors were developed as described under "Calibration/Validation Approach."
A geographic information system (GIS) using MapInfo was developed to help visualize and analyze the three factors. Street segments were assigned a point value depending on if they qualify as critical pedestrian corridors, are pedestrian generators or have high-pedestrian volumes.
Deficiency Index - The Deficiency Index uses surrogates for ease of street crossing (e.g., traffic speed, traffic volumes, and roadway width), sidewalk continuity (i.e., sidewalk inventory data), and street connectivity (i.e., street segment length). These factors were based in part on factors established by 1,000 Friends of Oregon (1993) in developing Pedestrian Environment Factors (PEFs) for the region. Pedestrian accident locations also are considered. Like the Pedestrian Potential Factor, the Deficiency Index tabulates the factors separately then combines the points, and illustrates the high-, medium-, and low-deficient areas using GIS.
To identify pedestrian factors for the Pedestrian Potential Index, Portland Metro developed a model using trips of two miles or less that were taken from the 1994 regional household travel survey and then geocoded by address. Using the Metro Regional Land Information System (RLIS) model, variables were developed such as intersection density per acre, average parcel size, slope, number of households and employment within one-half mile of each activity center. The travel data and variables were used to construct a binomial logit equation that showed the likelihood of walking for a given trip. The variables that were chosen for the Pedestrian Potential Index were well correlated with pedestrian demand.
Pedestrian Potential Index: The following data are used for developing this index:
Deficiency Index: Sidewalk inventory data, traffic speed, traffic volume, roadway width, length of the street segment, and pedestrian crash locations are used for developing this index.
Potential Data Sources:
The method uses a GIS. The software package MapInfo was used; other GIS packages could also be used.
A user should be proficient in GIS because the method uses spatial analysis tools to determine the highest potential and most deficient areas.
It is assumed that the potential pedestrian activity in the area can be adequately indicated using the available land use and activity variables.
Facility Design Factors:
The method uses two indices to account for facility design factors: Pedestrian Potential Index and Deficiency Index. The factors considered in each are listed under "Inputs/Data Needs."
The output consists of points according to street segment and factor, which are combined into two separate groups to formulate the Pedestrian Potential Index and the Deficiency Index. The street segments are classified by color in the GIS to illustrate the pedestrian potential or the deficiencies of the physical environment. The priority projects for future funding would be projects that rank high for both indices.
The city of Portland, OR analyzed 91 projects that were classified as Pedestrian Districts, Main Street and Pedestrian Corridor projects. Each project received a Pedestrian Potential score and a Deficiency score that combined the street segment index points that were within the projects' boundaries.
The final proposed projects were prioritized using the Potential and Deficiency Index rankings, community input, and cost-effectiveness evaluations.
Ellen Vanderslice, City of Portland, OR, Office of Transportation, Transportation Engineering and Development, 1120 SW 5th Avenue, Room 802, Portland, OR 97204.
City of Portland, OR, Office of Transportation. Identifying Priorities for Pedestrian Transportation Improvements. Pedestrian Master Plan Project Development: Final Report, June 1997.
Evaluative Criteria: How Does It Work?
The method provides two different ways to calculate the potential benefits of proposed pedestrian facilities. The first approach highlights the high-potential pedestrian areas that tend to have a functioning pedestrian environment while the second method focuses on functionally deficient areas where pedestrian activity is less likely to occur. These two indices were developed in recognition that there are two philosophies about how to spend pedestrian monies: improving high-pedestrian potential areas or improving areas of high deficiencies.
Use of Existing Resources:
The method uses an existing travel survey as well as land use information.
Travel Demand Model Integration:
The method was not designed for model integration.
Applicability to Diverse Conditions:
Variations of the indices could potentially be applied in other areas, based on local data availability. However, not all metropolitan areas will have land use data at the level of detail used in these specific indices.
Usage in Decision-Making:
The method was developed to help prioritize proposed pedestrian projects in the city of Portland's Pedestrian Master Plan. Neighborhood support and cost-effectiveness evaluations also were used. For the most part, projects that scored high for Pedestrian Potential scored low for Pedestrian Deficiencies, indicating that areas with high potential had already been developed for the most part with a functioning pedestrian environment. Nevertheless, the indices were still viewed as useful for helping prioritize projects.
Ability to Incorporate Changes:
The inputs can be easily revised in the GIS.
The use of GIS allows the user to easily understand the inputs and their effects on the final output.
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Keywords: Bicycle, Pedestrian, Travel demand, Forecasting methods, Estimate.