PLACER COUNTY TAAS SEGMENT ANALYSIS TOOL USER MANUAL
Prepared By: Fehr & Peers 2990 Lava Ridge Court Suite 200 Roseville, CA 95661 916.773.1900
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PLACER COUNTY TAAS SEGMENT ANALYSIS TOOL USER MANUAL
SUMMARY
Placer County-Maintained Routes
The TAAS Segment Analysis Tool segments Placer County’s roadway data (in GIS-compatible format) according to user-provided criteria, including segment length and percent segment overlap. The Segment Analysis Tool is programmed to locate and enumerate collisions near each segment. If traffic count information is available, a traffic rate calculation is performed. However, the results of this calculation should not be considered definitive in some cases, as robust collision rate calculations are dependent upon the extent and availability of traffic count data (see the process description in the “Running the Tool” section for additional details). The Segment Analysis Tool produces a layer within ArcMap identifying high incidence collision locations. Depending on the use of the tool’s optional analysis, the attribute table associated with the layer may include fields containing number of collisions per segment or corridor, the number of collisions that occurred at intersections, collision density, and collision rate.
USAGE
Traffic Counts
Collisions
Segment Analysis
Output Layer Identifying High Incidence Locations
CONTACT INFORMATION Amy Smith Fehr & Peers 916.262.7377 a.smith@fehrandpeers.com
Number of Collisions at Intersections
Tool Outputs
Number of Collisions per Segment
This tool may be used to analyze collision frequency along Placer County Maintained Routes. Collision rate can be calculated along County Maintained Routes where traffic volume information is available in GIS format. Collision densities can be reported for general roadway network data.
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Placer County Roadway Network Tool Inputs
The TAAS Segment Analysis Tool is a custom GIS tool that works within ArcMap. The tool uses route, network, and collision data to locate and assess collision patterns along roadway segments in Placer County.
Collision Density
Collision Rate
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TABLE OF CONTENTS Opening the Tool
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Tool Inputs
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Running the Tool
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Tool Outputs
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Finding Information
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Additional Resources
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OPENING THE TOOL How to open the tool from your MXD 1. 2.
Extract the “TAAS_Segment AnalysisTool.zip” archive provided by Fehr & Peers. Double click to open “TAAS_SegmentAnalysis.mxd”. ArcMap will load the map document, which contains the following layers: • • • • • • • • •
Collisions_2010* trafficCounts* CountyMaintainedRoutes* RoadNetwork Intersections PlacerCityLimits Hydro_Linear Hydro_Poly PlacerCountyBoundary
*Provided by Placer County Department of Public Works - Transportation
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3.
Navigate to the Placer County Tools toolbox in the ArcMap Catalog window. If the Catalog window is not open, click on Windows > Catalog.
4. Double click on the “TAAS Segment Analysis Tool” to open the tool dialog box.
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TOOL INPUTS About the Input Fields The Segment Analysis Tool inputs are available as layers included in the SegmentAnalysis.mxd map document and associated geodatabase (SegmentAnalysis.gdb). Enter inputs by 1) Dragging and dropping from the Catalog Window into the appropriate input field, 2) Selecting layers from the drop-down menu, or 3) browsing to inputs on a file system. Optional inputs are indicated by the term “Optional” in parentheses. Click the “Show Help” button and select any input field to learn more about individual inputs. The Segment Analysis Tool includes three analysis options: 1) Segment Analysis (default analysis), 2) Collision Rate Analysis (optional), and 3) Road Network Analysis (optional). Below is a screen capture of the Segment Analysis component of the Segment Analysis Tool dialog box with suggested inputs.
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The Segment Analysis component of the Segment Analysis Tool is the default analysis and is required when running the tool. This analysis segments the County Maintained Routes layer according to a user-defined study segment length and percent overlap and performs a spatial query to locate nearby collisions. Segment Analysis inputs Include: • Input Workspace (SegmentAnalysis.gdb Geodatabase): The geodatabase containing the input features. • Required Features Included in the SegmentAnalysis.gdb Geodatabase Workspace: 1. County Maintained Routes (Line Feature Class with M Values*) 2. Collisions (Point Feature Class) 3. Study Segment Length (Miles) 4. Study Segment Overlap (Percent) • Optional Features Included in the SegmentAnalysis.gdb Geodatabase Workspace: 1. Intersections (Polygon Feature Class) 2. Traffic Counts (Line Feature Class) 3. Road Network (Line Feature Class) • County Maintained Routes: Routes (line feature class) to be analyzed using the TAAS Segment Analysis Tool. • Feature class must include: 1. “ROADNUM” field containing alphanumeric identifier for county-maintained routes. 2. M values* • Collisions: Collisions (point feature class) to be included in the analysis. • Study Segment Length (Miles): Length of route segments in miles. • Study Segment Overlap (Percent): Percent at which segments will overlap. For example, if a ¼ mile long segment is specified in the “Study Segment Length” input field with a 25% overlap, the number of collisions within a ¼ mile segment will be recorded, then the analysis segment will advance 1/16 mile and the number of collisions within this new ¼ mile segment will be recorded. • Intersections (optional): A polygon feature class representing the area surrounding an intersection within which any collisions are considered to have occurred at an intersection. This feature class can be generated by creating a buffer around intersection points in a network. A buffer of 150 feet will classify all collisions falling within the buffer as intersection collisions. • Segment Analysis Output Feature Class: The name and location of the feature class to contain the results of the segment analysis.
* M values are used to measure distances along linear features. M values can be generated for linear features using the ArcGIS Linear Referencing toolbox. Visit this site to learn more: http://resources.arcgis.com/en/help/main/10.1/index.html#//003900000002000000
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Below is a screen capture of the Collision Rate Analysis component of the Segment Analysis Tool dialog box with suggested inputs.
The Collision Rate component of the Segment Analysis Tool is optional. The Collision Rate Analysis uses traffic count data provided by Placer County. Traffic count features are included in the SegmentAnalysis.gdb geodatabase. When selected, this analysis associates traffic count data with nearby segments to estimate collision rate for each segment. Collision Rate Analysis Inputs Include: • Traffic Counts: Traffic counts (line feature class) for use in calculating collision rate for county-maintained roads with available data. • Feature class must include: 1. Text/String field containing the date of each traffic count, formatted as “d/m/yyyy” (See “Date Field” input below) 2. Numeric field containing Average Daily Traffic (ADT) volumes for county-maintained roads (See “ADT Field” input below) 3. “ROADNUM” field containing alphanumeric identifier for county-maintained routes. • Date Field: Text/String field containing the date of each traffic count, formatted as “d/m/yyyy”. The most recent traffic counts will be applied in the Collision Rate analysis. • ADT Field: Numeric field containing Average Daily Traffic (ADT) volumes for county-maintained roads. Volumes will be aggregated according to route, such that each route is associated with one ADT volume value. • Number of Years: Number of years included in the collision analysis. • Selected Route ADT: ADT value associated with selected county-maintained route. This input is optional and should only be provided when an individual county-maintained route is selected for analysis.
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Below is a screen capture of the Road Network Analysis component of the Segment Analysis Tool dialog box with suggested inputs.
The Road Network component of the Segment Analysis Tool is optional. The Road Network Analysis calculates the number of recorded collisions for individual roadway features. Road Network features are included in the SegmentAnalysis.gdb geodatabase. Road Network Analysis Inputs Include: • Road Network: The road network (line feature class) to be analyzed. • Road Network Analysis Output: The name and location of the feature class to contain the results of the road network analysis.
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How to Enter Inputs Segment Analysis Tool inputs can be entered using the following methods: 1. Dragging and dropping from the Catalog Window into the appropriate input field. 2. Selecting layers from the drop-down menu. 3. Browsing to inputs on a file system. Click the “Show Help” button and select any input field to learn more about individual inputs.
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RUNNING THE TOOL How to Run the Tool The Segment Analysis Tool is designed to run within the SegmentAnalysis.mxd map document in ArcMap. To run the tool: 1. Open the SegmentAnalysis.mxd map document and navigate to the Segment Analysis tool in the Catalog Window. If the Catalog window is not open, click on Windows > Catalog. 2. Double click on the “TAAS Segment Analysis Tool” to open the tool dialog box. 3. Enter input parameters from SegmentAnalysis.gdb geodatabase (see “Tool Inputs” section for more information on required and optional input parameters). 4. Click “OK” to run the tool. The screen capture below shows the Segment Analysis Tool dialog box with suggested inputs.
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Process Description The Segment Analysis Tool performs a step-wise scan of County Maintained Routes based on two user-defined settings: 1. Analysis segment length. 2. Percent overlap. For example, if a ¼ mile long segment was selected with a 25% overlap, the number of collisions within a ¼ mile segment would be recorded, then the analysis segment would advance 1/16 mile and the number of collisions within this new ¼ mile segment would be recorded. The scan would proceed step-wise for the length of each route. The Segment Analysis Tool is capable of performing the step-wise scan for a subset of specified route(s) or for the entire network of County Maintained Routes as described above. If the final segment of a roadway is shorter than the user-defined analysis segment length, the Segment Analysis Tool will append it to the preceding analysis segment. Consequently, there will be some variability in analysis segment length (up to two times the user-defined setting) so that small portions of the roadway network at its boundaries are not left out of the step-wise scan. The Segment Analysis Tool accounts for intersection-related collisions in the scan of the County Maintained Routes. An intersection is defined to include 150 feet of each approach leading into the intersection. Intersection-related collisions will be included in collision data used by the Tool. The Tool will provide ranked listing of top collision locations, which includes the intersection-related collisions. The tool output identifies the number of intersection-related collisions as well as segment-related collisions. The user has the option to deselect any segments from the ranked list based on engineering judgment. The optional Collision Rate Analysis component of the Segment Analysis Tool includes the ability to use the traffic volume information within the GIS to calculate collision rates where traffic counts are available. This component uses only the most recent traffic count data included in the input traffic count feature class. Due to varyiations in the extents of segment geometry and traffic count input geometry, traffic volumes in the input data may represent only a portion of each segment being analyzed. The optional Road Network Analysis component of the Segment Analysis Tool identifies the number of collisions, roadway length, and collision density (collisions per mile) on all roadways in the provided road network feature class.
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TOOL OUTPUTS About the Outputs The Segment Analysis Tool outputs will vary depending on user-defined inputs for default and optional components. Results can be viewed both graphically as symbolized map layers and in tabular format using output layer attribute tables. The results of the default Segment Analysis component will always include a line feature class representing segmented County Maintained Routes. An additional feature class will be created if the appropriate inputs are entered for the optional Road Network Analysis component. The optional Collision Rate component will add additional fields to the Segment Analysis output feature class attribute table. These results can be accessed by opening the Segment Analysis output feature class attribute table. Below is a description of output feature classes and associated fields included in the attribute tables of the output feature classes. Segment Analysis Output The Segment Analysis Tool output will automatically be added to the map document and symbolized according to number of collisions located along each segment. Segments with the highest incidences of collisions are demarcated in red. Below is a screen capture displaying an example of the Segment Analysis Tool defult output that is automatically added to the SegmendAnalysis.mxd map document. Feature symbolization can be adjusted in the map layer’s properties dialog box.
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In addition to the graphical output, Segment Analysis results can be accessed in tabular format by opening the attribute table of the output feature class (see example table below). To open the attribute table, right click on the layer name in the map document table of contents and select “Open Attribute Table” from the menu. The Segment Analysis output table will include all fields associated with the County Maintained Routes feature class as well as the following additional fields: • FROM_: This field contains the post mile at which the segment begins. • TO: This field contains the post mile at which the segment ends. • INTERSECTION: This field contains the number of collisions occuring at an intersection. Any collision falling within 150 feet of two intersecting roadway features is considered an intersection collision. • COLLISIONS: This field contains the total number of collisions located along each segment. • ROAD_NAME: This field contains the road name of the segment. Fields not listed here may be included in the table if the Collision Rate component was included in the analysis, or if additional analysis was performed using the Segment Analysis output feature class.
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Collision Rate Analysis Output If the user provides the appropriate inputs for the Collision Rate component of the Segment Analysis, the following fields will be added to the Segment Analysis output feature class attribute table: • ADT: This field contains traffic volumes derived from the user-specified Traffic Counts input feature class. • DATE: This field contains the traffic count date derived from the user-specified Traffic Counts input feature class. • DISTANCE: This field contains the length of the segment, which determines whether a spot collision rate or segment collision rate is calculated (see the “Process Description” section for more on how collision rate is calculated). • SPOT_RATE: If the segment length indicated in the DISTANCE field is less than or equal to 0.5 miles and Traffic Count features are available along the segment, this field will contain the spot collision rate. • SEG_RATE: If the segment length indicated in the DISTANCE field is greater than 0.5 miles and Traffic Count features are available along the segment, this field will contain the segment collision rate.
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Road Network Analysis Output If the appropriate Road Network Analysis inputs are specified by the user, the Road Network Analysis output will automatically be added to the map document and symbolized according to number of collisions located along each individual roadway feature. Features with the highest incidences of collisions are demarcated in red. Below is a screen capture displaying an example of the Roadway Network Analysis output that is automatically added to the SegmendAnalysis.mxd map document if included when running the tool. Feature symbolization can be adjusted in the map layer’s properties dialog box.
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In addition to the graphical map output, Roadway Network results can be accessed in tabular format by opening the attribute table of the output feature class (see example table below). To open the attribute table, right click on the layer name in the map document table of contents and select “Open Attribute Table” from the menu. The Segment Analysis output table will include all fields associated with the Roadway Network input feature class as well as the following additional fields: • LEN_MILES: This field contains the length of the roadway feature in miles. • COLL_DENS: This field contains the collision density (collisions per mile) for each roadway. • INTERSECTION: This field contains the number of collisions occuring at an intersection. Any collision falling within 150 feet of two intersecting roadway features is considered an intersection collision. • COLLISIONS: This field contains the total number of collisions located along each segment.
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FINDING INFORMATION Viewing Output Layers Segment Analysis Tool outputs are automatically added to the SegmentAnalysis.mxd map document. Output parameters such as output feature class name and location are defined by the user. The following screen captures show sample output parameters and map layers added in ArcMap after the tool has completed its analysis. Sample Segment Analysis Tool Dialog Box with Suggested Inputs and Defined Output Parameters
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Sample Segment Analysis Results
Sample Roadway Network Analysis Results
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Reading Output Tables Segment Analysis Tool output layer attributes can be accessed within ArcMap. To open a layer’s attribute table, right click on the name of the layer in the table of contents and select “Open Attribute Table” (see screen capture below for example of “Open Attribute Table” option).
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The following screen captures are examples of Segment Analysis Tool output tables. These tables provide access to tabular data associated with map layer outputs. Visit the “Tool Outputs” section of this document for more information on Segment Analysis Tool outputs. Default Segment Analysis Output Table with Additional Collision Rate Analysis Output Fields
Road Network Analysis Output Table
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Sorting and Querying Tables To sort output tables viewed in ArcMap according to any field, right click on the field name and select one of the sort options (see example in screen capture below).
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In addition to sorting values, output tables can be queried using the “Select by Attributes” dialog box. To access the dialog box, click on the “Select by Attributes” button above the attribute table (see example in screen capture below).
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Attribute tables can be queried using the Structured Query Language (SQL). The example SQL query in the screen capture to the left will return segments with greater than 5 non-intersection collisions. Query results will be highlighted in the attribute table being queried (see example in screen capture below). Results will also be highlighted in the map layer associated with the attribute table (see example in screen capture on next page).
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Highlighted SQL Query Results
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Exporting Tables Segment Analysis Tool output tables can be easily exported from ArcMap into a variety of formats, including Esri dBase tables (.dbf) and text files (.txt). To export a table, click on the table drop-down options menu and select “Export” (see example in screen capture below).
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ADDITIONAL RESOURCES ArcGIS Desktop Help: http://help.arcgis.com/en/arcgisdesktop/10.0/help/
Building Query Expressions in ArcGIS: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Building_a_query_expression/00s50000002t000000/
Using Select by Attributes: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Using_Select_By_Attributes/00s500000021000000/
Displaying Map Layers:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/A_quick_tour_of_displaying_layers/00s500000019000000/
Fehr & Peers
http://www.fehrandpeers.com/ ASAP http://asap.fehrandpeers.com/
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