The combined score is then penalized by subtracting the barriers index, sidewalk and bike lane gap index, and estimated average cycling time to the four adjacent cells. Recognizing that these factors impede, but generally do not completely prevent cycling access, each penalty criteria is discounted by 50% to reduce its overall impact on the score. The cycling time was estimated using the Google Directions API, and averaged across four of the nearest cells, providing an estimate of how connected a cell is to neighboring cells. The longer the cycling time, the higher the penalty. A cell with high network density, bike lane lengths, and services within a mile; and low sidewalk/bike lane gaps, barriers, and walking time is assigned a high (cycling accessibility) potential index. An example calculation for the Cycling Accessibility Index is provided in Table 4.
Table 3. Criteria used to develop the Cycling Accessibility Index.
Criteria Services
Description
Combined
Density of nonresidential parcels within a 1-mile radius of the center of the grid cell (based on DOR code). Density of roadway intersections within a grid cell (excluding culs de sac and major roadways).
Network
Bike lane
Total bike lane length within the cell.
Local Roadway
Centerline length of local roadway within a grid cell. Local roads were selected by their approximate speed limit (<=25) Subtract the barrier index from the combination above. Subtract the sidewalk gap index from the combination above Subtract the average bicycling time to the four closest adjacent cells.
Subtract (Discount each by 50%)
Barriers
Gaps in Sidewalks and Bike lanes Estimated Google Directions Bicycling Time
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