3.2 Study Area Zones for Origin/Destination Analysis
3.2.1 Definitions of Zones Zones: polygons used to aggregate trips. These are treated as origins and destinations within the study area. Nodal zones are based on aggregating areas of activity (nodes) and activity areas within communities. Trips: is a representation of activity based on the Streetlight Trip Index. May sometimes be refer red to as traffic. “StreetLight Trip Index represents trip activity but does not indicate actual number of trips or vehicles. The values are provided on an index. Personal and Commercial values use different indices. Projects in the US and Projects in Canada also use different indices.” 3 The index approach allows samples from the same areas and time periods to be comparable. Personal: A StreetLight designation that defines trips for personal non-commercial use. It is based on a sample from smart-phone applications. Commercial: A StreetLight designation that defines trips for commercial non-personal use. It is based on a sample from GPS data. Gates: polygons used to determine trips that pass through specific roads. For example, a gate on the north side of the study area placed on I-75 was used to determine the number of trips that pass through that roadway. Trips based on the StreetLight Index. Home-Based Work (HBW ) : StreetLight attribute used for trip purpose, travel between home and work in either direction. “To calculate this metric, all trips in the analysis are evaluated to determine whether their origin zones are also the devices’ expected home or work locations. (In contrast, our Simple Trip Purpose Metrics use the parcel data associated with trips’ orig in zones to assign a trip purpose of ‘residential, commercial, or other.’)” 4 Home-Based Other (HBO): StreetLight attribute used for trip purpose, travel to or from home, to anywhere other than work. See above for how this metric is calculated. Non-Home Based (NHB): StreetLight attribute used for trip purpose, all travel not to or from home. See above for how this metric is calculated. 3.2.2 Methods for Identifying Zones Zones used for the OD analysis were derived in two ways. Nodal zones were developed by aggregating major activity areas within communities. From these nodal boundaries, a 5-minute walking (10-minute biking) service area was used to expand activity areas to encompass areas that were within a reasonable walking/biking distance. To derive the service area, all land use centroids within the areas of activity (node) were selected, and the ArcGIS Network Analyst extension was used to calculate a 10 minute bicycle
3 Gische, Kimberly 2018 “StL Trip Index”, https://support.streetlightdata.com/hc/en -us/articles/360018552772-StL- Trip-Index 4 Gische, Kimberly 2018 „July 11 th , 2017” https://support.streetlightdata.com/hc/en -us/articles/360017709491-July- 11th-2017
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