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101 A p p e n d i x F The Roadway Information Database (RID) was built on an underlying, route-measure-based linear referencing system (LRS). Other roadway features, such as those identified in S04B, have been conflated to this LRS and are represented as individual features within an Esri ArcGIS geodatabase. Each feature also possesses corresponding LRS-based route and measure values. Therefore, the RID supports both attribute- and spatial-based queries, as well as dynamic segmentation. Dynamic segmentation may be used to overlay multiple, inde- pendently maintained, and disparate data sets to identify loca- tions satisfying specific conditions. Below is a step-by-step example of how the process can be used to answer a research question. The research objective for this example is to identify rural, two-lane horizontal curves in North Carolina with shoulder widths less than 6 ft. (This was completed before the final miles in North Carolina were collected in 2013.) F.1 Step 1: identify data needed Identify the data sets necessary to satisfy the objective. The following are the required data sets and corresponding sources: ⢠Two-lane roads: S04B Lane data. ⢠Shoulder width: S04B Shoulder data. ⢠Horizontal curves: S04B Alignment data. ⢠Rural areas: U.S. Census urban area boundaries data. F.2 Step 2: Select Two-Lane Highways The S04B lane data provide the number of lanes and lane types for all roadways collected in both directions. This step uses an attribute-based query to select only two-lane roads. 1. Import S04B Lanes data. 2. Open the selection tool Select By Attributes. 3. Use the query shown in Figure F.1, which uses the Through- Lanes, LeftTurnLanes, and RightTurnLanes attributes from the S04B Lanes data. 4. Right-click on the S04B Lanes layer, select Data, select Export Data . . . 5. Export the selected lanes as TwoLaneHighway.shp (Fig- ure F.2). This shapefile is used in Step 6. Because the S04B data are collected in both directions, a value of one for ThroughLanes would select any two-lane roadways. The LeftTurnLanes and RightTurnLanes attributes were used to remove any locations with turn lanes. F.3 Step 3: Select Shoulders Less Than 6 ft The S04B Shoulder data provide shoulder type and width for all roadways collected. This step uses an attribute-based query to select shoulders that have a width less than 6 ft. 1. Import S04B Shoulder data. 2. Open the selection tool Select By Attributes. 3. Use the query shown in Figure F.3, which uses the Width attribute to select shoulders that are less than 6 ft. 4. After the selection, right-click on the S04B Shoulder layer, select Data, select Export Data . . . 5. Export the selected shoulders as ShoulderLessThanSix.shp (Figure F.4). This database file is used in Step 7. The S04B Shoulder data provide the shoulder width as part of the Width attribute. A âless thanâ query was used because the research objective is to find all shoulders less than 6 ft. Roadway Information Database Operating Procedures
102 Figure F.1. Query to select two-lane highways. Figure F.2. Export selected two-lane highways.
103 Figure F.3. Query to select shoulders less than 6 ft. Figure F.4. Export shoulder less than 6 ft.
104 F.4 Step 4: Select Curves The S04B Alignment data define whether a roadway is a tan- gent or curve, along with the radius of the curve. This step again uses an attribute-based query to select the curve from the S04B Alignment data. 1. Import S04B Alignment data. 2. Open the selection tool Select By Attributes. 3. Use the query shown in Figure F.5, which uses the Tangent attribute to select only the curves. 4. Right-click on the S04B Alignment layer, select Data, select Export Data . . . 5. Export the selected curves as Curves.shp (Figure F.6). This shapefile is used in Step 5. The S04B Alignment database uses the Tangent attribute to distinguish between tangents and curves. A value of zero for Figure F.5. Query to select curves. Figure F.6. Export selected curves.
105 Figure F.7. Query to select rural curves. this attribute is used to identify curves. The curves are reduced further in Step 5. F.5 Step 5: Select Rural Curves This step uses the Curves.shp created in Step 4 and the Urban Boundary from the census data to select curves located in rural areas. A spatial selection is used to select all curves within the urban boundaries. 1. Import Urban Boundary from census data and Curves.shp from Step 4. 2. Open the selection tool Select By Location. 3. Use the settings shown in Figure F.7 to use the spatial selection. This selects all the curves within the urban boundaries. 4. Because all rural curves are desired, the selection must be reversed. Right-click on the Curves layer and select Open Attributes Table. 5. Select Switch Selection ( ), which switches the selection from urban curves to rural curves. 6. The selected curves can now be exported. Right-click on the Curves.shp, select Data, select Export Data . . . 7. Export the selected rural curves as RuralCurves.shp (Fig- ure F.8). This shapefile is used in Step 6. F.6 Step 6: dynamic Segmentation of Rural Curves and Two-Lane Highways The first dynamic segmentation is completed using the Rural Curves.shp from Step 5 and the TwoLaneHighway.shp from Step 2. This step selects any locations where both attributes are present. 1. Import TwoLaneHighway.shp from Step 2 and RuralCurves .shp from Step 5. 2. Under the Linear Referencing Tools, select Locate Features Along Routes (Figure F.9). 3. To perform dynamic segmentation, use the RouteID, FrMeasure, and ToMeasure attributes from each database file, as shown in Figure F.10. These are part of the linear referencing system and are used to select rural curves and two-lane highways that are at the same location on the network. 4. For the Output Event Table, name the table RuralTwoLane Curve. The table created from this will be a database file that can be plotted using the linear referencing system. 5. To plot the RuralTwoLaneCurve event table created, the S04B Routes data needs to be imported. 6. Right-click on the RuralTwoLaneCurve event table and select Display Route Events . . .
106 Figure F.8. Export rural curves. Figure F.9. Dynamic segmentation tool. Figure F.10. Dynamic segmentation of rural curves and two-lane highways.
107 8. Right-click on the FinalCurve Events, select Data, select Export Data . . . 9. Export the selected rural two-lane curves with shoulders less than 6 ft as FinalCurve.shp. Exported is a layer with the final list of curves that are located in a rural area, on a two-lane highway, and with a shoulder less than 6 ft. All the attribute data from the S04B Lanes, S04B Align- ment, and S04B Shoulders have been retained and included in the final layer. These steps resulted in three reductions of the curves using three S04B data elements (Figure F.13). North Carolina originally had 8,414 curves as part of the mobile data collec- tion, which was reduced to 854 curves of interest. The result is a layer with all locations that are on a curve, on a two-lane highway, have a shoulder less than 6 ft, and are in a rural area in North Carolina. Multiple other data elements can be used to refine the results further. Other attributes can also be used to narrow/broaden results for each data element. Figure F.11. Display route events. 7. Use the selections shown in Figure F.11, which create a RuralTwoLaneCurve Events layer. 8. Right-click on the RuralTwoLaneCurve Events, select Data, select Export Data . . . 9. Export the selected rural two-lane curves as RuralTwoLane Curve.shp. This shapefile is used in Step 7. The RuralTwoLaneCurve.shp now shows all locations where the rural curves and two-lane highway are both present. This shapefile now contains all data from both layers and can be used again for dynamic segmentation. F.7 Step 7: dynamic Segmentation of Rural Two-Lane Curves and Shoulders with Width Less Than 6 ft The second dynamic segmentation uses the RuralTwoLane Curve.shp from the first dynamic segmentation in Step 6 and ShoulderLessThanSix.shp from Step 3. The same process is followed as in Step 6. 1. Import RuralTwoLaneCurve.shp from Step 6 and Shoulder LessThanSix.shp from Step 3. 2. Under the Linear Referencing Tools, select Locate Features Along Routes (Figure F.9). 3. To perform dynamic segmentation, use the RouteID, FrMeasure, and ToMeasure attributes from each database file, as shown in Figure F.12. 4. For the Output Event Table, name the table FinalCurve. 5. To plot the FinalCurve event table created, the S04B Routes data needs to be imported. 6. Right-click on the FinalCurve event table and select Display Route Events . . . 7. Use the selections shown in Figure F.11, which will create a FinalCurve Events layer.
108 Figure F.12. Dynamic segmentation of rural curves on two-lane highways and less than 6 ft shoulder. â Figure F.13. Dynamic segmentation curve reduction.
