Introduction

The SWITRS GIS Map offers an interactive map-centric approach to viewing and querying SWITRS collision data. To use this tool, click on SWITRS GIS Map from the Tools dropdown menu. Then, click on Click Here to Open SWITRS GIS Map. This user guide provides instructions on how to use the tool's many different functions.

Web Browser Compatibility

The SWITRS GIS Map is designed to run in many different web browsers. For optimal viewing experience and full functionality, we recommend the latest versions of Internet Explorer, Mozilla Firefox, or Google Chrome.


Page Layout

  1. Map SWITRS Panel

  2. The Map SWITRS panel is displayed on the left side of the browser window. All the functions to query SWITRS can be found in this panel. It can be minimized to the left by clicking on the arrow in the top right corner. If you are using a small screen, you can also collapse the different categories by clicking on the title menu bar for Date, Location, or More Factors. Selected factors will be shown at the bottom of the panel.
  3. Toolbar

  4. The navigation toolbar, tools, map contents, basemaps, and location search bar are located in the horizontal bar across the top of the map.
  5. Map

  6. The Map is the main component of the application; it is where collisions and other data layers are displayed. Other windows can be minimized to maximize the map extent.
  7. Results

  8. The results window is shown hovering over the map in the top right corner. After showing collisions on the map it will automatically expand to summarize the results and give several options to interact with the data. It will also notify users when the collision display limit has been exceeded.
  9. Overview Map

  10. The overview map is in the bottom right corner. The current extent is shown as a gray box. By dragging the gray box, users can pan the map display. Minimize the overview map by clicking the arrow in the bottom right corner.

1. Map SWITRS Panel

The core functionality of the SWITRS GIS Map is the ability to query and dynamically map the collision data. Many options are available in the Map SWITRS panel.

Date and Location Parameters

Users must first establish a time frame and county/city location. The To and From dates can be selected from a calendar or typed into the Date box. The ten most current years of data are available to query. Note that the most current year available may be a provisional set and only a portion of the final collision records that will eventually be available. Please refer to the FAQs for more information.

Select Collision/Party/Victim Factors

Next, users have the ability to select specific types of collisions based on collision, party or victim specific factors. For example, pedestrian collisions involving older adults could be specified by choosing Pedestrian Collision > Yes in the collision factors and specifying in the victim factors, Victim Age > 65 to 125. When a field such as the Collision Factors > Month is chosen, clicking the Check All or Uncheck All option will check the boxes accordingly.

Refer to the codebook in the Help page for more information regarding the fields. Only the most commonly used fields are available to query by in the SWITRS GIS Map tool. The Resources page also gives you more information about Working with the relational database structure that SWITRS data is organized in.

Select State Highway

Users have a final option of narrowing their query based on a state highway designation. The default for this field is ALL, which means that all of the collisions that satisfy the selected time, location, and other selected factors will be shown. Choosing No State Highway will only show collisions not associated with the state highway system.

Finally, choosing

  • State Highway Only
  • (and by default, ALL state highways and ALL directions) will show only collisions associated with the state highway. You can also select a specific state route number and its direction. Otherwise, all state routes in the county/city will be included.

    Selected Factors window

    After choosing factors, the Selected Factors window in the bottom left corner will populate with the list of factors in real-time. To remove a factor, hover over that factor and then click on the circle X that then appears to the left. Update the displayed collisions by clicking on the Apply button; the selected collisions will then appear on the map.

    Identify Collisions/Collision Details

    Once the collisions are displayed on the map, you can click on them to get more details. A pop-up will show details about the collision and location. If more than one collision is in the same location, you will see x of total number of collisions in the top left of the dialog. To navigate through the different collisions, click on the small arrows in the top right of the dialog window. There are also three options across the bottom of the pop-up.

    • Zoom to: Zooms your map closer into that collision on the map.
    • Street Preview: Opens up a pop-up image of that collision's street scenery via Google Maps.
    • Collision Details: Opens a new page with a small map, the basic details, and a Google Street View; this page provides an easily printable 1 page summary of the crash.

    Display Options

    There are several different ways to symbolize collisions. Display options can be changed by clicking Options in the Map SWITRS panel. By default, collisions are shown as points on the map, but they can also be displayed as clusters or as a heatmap.

    Display

    Collisions Displayed As

    • Points: The default view displays each collision as a yellow square on the map. All tools and features are available for this view.
    • Clusters: Clusters aggregate nearby collisions into single larger points. This helps to synthesize areas with large numbers of collisions. Clusters change color and size depending on the number of records represented in white text. Clicking on a cluster shows gray dots of each of the individually represented collisions and the details page can be accessed for each of them.
    • Heatmap: When heatmap is selected, collisions will be displayed as a matrix of colors, where the dependent variable is the density of collisions. Blue regions represent lower numbers of collisions while red areas represent the highest collision counts.

    Display City Boundary

    By default, Display City Boundary will be checked on. Uncheck this option to turn off the outlined, semi-transparent blue city layer.

    Display City Boundary: On

    Display City Boundary: Off

    Tip: If you are displaying the collisions as a heatmap, turn off this layer so that the heatmap can be displayed more clearly.

    Symbols

    When the default Points style is active, you can also choose to display the collisions as symbols stratified by either Collision Severity or Motor Vehicle Involved With. After selecting a type of stratification, you can then choose to turn on/off colors for each value.

    Explore collision data by using a combination of these display options. The heatmap and cluster options help synthesize large numbers of collisions in the same or similar location. Symbology options help show how different types of collisions are distributed.


    2. Toolbar

    Navigation Tools

    Several options are available for navigating the map. When no other tools are active you can pan the map by left-clicking and holding. You can zoom in/out by using the mouse scroll wheel or the zoom slider in the upper left portion of the map. The toolbar also has several navigation functions:

    • Zoom in: Click and drag to draw a rectangle around an area to zoom in on.
    • Zoom out: Click and drag to draw a rectangle around the area to zoom out of.
    • Zoom to full extent: Gives you view of the world map.
    • Zoom to previous extent: Takes you to the previous screen that was zoomed in/out of.
    • Zoom to next extent: Takes you to the next screen that was zoomed in/out of
    • Pan: Move around the map by left-clicking and holding.

    Deactivate

    Any active tools can be deactivated by clicking the Deactivate button. This clears the function and makes a left-click revert to panning.

    Measurement Tools

    Use a Measurement Tool to find the area, distance, or location of a polygon, polyline, or point, respectively. These measurements can be taken in different units by simply selecting the desired unit from the dropdown menu. Measurement results are shown at the bottom of the pop-up dialog.

    • Area Measurement tool: Find the area of a region by clicking at each point of the polygon. Double-click to finish.
    • Distance Measurement tool: Find the distance of a polyline by clicking at each point. Double-click to finish.
    • Location tool: Click on a point on the map to determine the latitude/longitude coordinates.

    Printing

    Click the Print button in the toolbar to generate a portrait or landscape view of your map; you can save either as a PDF or JPG image file. Selected location and time parameters will be shown as the title of the map. The map printout will also display a scale bar and the date printed.

    Tools

    The SWITRS GIS Tools can be accessed from the toolbar across the top of the map.

    Spatially Select Collisions

    One of the most powerful features of SWITRS GIS Map is the ability to Select Collisions of interest in a region, corridor or intersection. After selecting the collisions, you can review the statistics, create a collision diagram, or download the complete data files to conduct further analyses. There are three different ways to select collisions.

    By Drawing

    The Select by Drawing tools allow you to draw a shape around the collisions that you want to select. Choose from either the Free Polygon (left) or Polygon (right) tool. Click your mouse to draw around the collisions and let go to complete your selection.

    By Buffer

    The Select by Buffer tools can give more precise measurements. For example, you may want to select collisions within 25 feet of a corridor (left), or 75 feet of multiple intersections (right).

    1. Enter a buffer distance.
    2. Type in the number of buffer rings (Buffer Count) to create.
    3. Choose a shape. Hovering over a shape button provides a description (e.g. Point, Multiple Points, Line, etc.).
    4. Follow the on-screen instructions on the map.

    Select by Buffer: Polyline
    25 ft, 2 Buffer Count

    Select by Buffer: Multiple Points
    75 ft, 1 Buffer Count

    By Area

    The Select by Area option allows you to select collisions that occur within one or more geographic zones: choose from Census tracts, traffic analysis zones (TAZ), and Zip codes. After selecting one of these three options, semi-transparent boundaries will be displayed on the map. Click within an area to highlight and select the collisions within it. You can also select multiple areas and deselect an area by re-clicking a highlighted area.

    Rank by Intersection

    Use the Rank by Intersection tool to rank major intersections by total collision count.

    After selecting Rank by Intersection from the Tools menu, select the distance that you want collisions to be included in an intersection's collision count. For each intersection, the higher its rank, the more collisions occurred within it.

    Compare the heatmap below with its ranked list of Top 10 Intersections (buffer of 100 ft). Notice that higher ranked intersections are red in the heatmap.

    Note: Only collisions that match your selected date, location, and other factors are used. Additionally, this tool only ranks collision counts for intersections in which one of the intersection's roads is a primary road or secondary road. Primary and secondary roads are any of the 10 types of roads listed in the A2 and A3 series. For more info, see this list of Census Feature Class Codes.

    Show FARS Data

    Click on Show FARS from the toolbar to map collisions from the FARS dataset.

    Most FARS collision points should overlap with the fatal collisions within your selected time frame. However, there will be a few cases where they do not, as highlighted below. This is due to differences in FARS and SWITRS records as well as the geocoding processes used.

    Note: For more information on FARS data, see the National Highway Traffic Safety Administration's FARS website.

    Map Contents

    Map Contents refer to the different layers that can be displayed on the map and is accessible from the main toolbar. Users can select from several standard layers or import one of their own point layers.

    Import Layers

    An important feature in the Map Contents is the ability to Import Layers that are saved on a local drive. This allows you to show previously queried SWITRS data from TIMS on the map alongside any current queries. It also allows other types of collision data to be displayed at the same time as well.

    To import point layers click on the Import Layers button and navigate to the appropriate file. There are currently two different ways to import a points layer:

    SWITRS csv file from TIMS

    If you have previously downloaded a csv file from any of the mapping applications on TIMS, then you can import it onto the map. An Imported Collisions window will display the total number of collisions mapped.

    Imported collisions will be displayed as aqua-colored squares and can be interacted with in a similar manner as collisions displayed from the Map SWITRS panel. Click on a collision to view its collision details. After importing a layer, the Map Contents menu will update with check boxes so that those layers can be turned on/off.

    Tip: A special drag and drop feature is only available for SWITRS csv files. This allows you to simply drag the csv file from your hard drive onto the map and display the collisions.

    Shapefiles

    Shapefiles can also be imported as layers. The shapefile components (*.shp, *.shx, *.sbn, *.sbx, *.dbf, *.prj) must be in a zip file (.zip). The zip file should then be selected in the Open window. The data fields will be shown in the pop-up window.

    Identify

    Use the Identify tool to learn more about a point or area that is currently displayed as a layer via Map Contents. First, make sure that the layer you are interested in is turned on. Then, activate the Identify function. Click on the map within one of the boundaries or on one of the individual symbols. A white triangle will show where you clicked on the map. If multiple layers are under that triangle, you can scroll through the layers using the arrows in the top corner of the pop-up window.

    Note: The Identify function only works for 'Map Contents' layers, not collisions. To identify collisions, deactivate the Identify function by activating another tool or clicking the Deactivate tool.

    Basemaps

    Switch to a basemap by clicking it from the Basemap dropdown menu. A basemap presents background referential information such as roads, landmarks, political boundaries, and landforms. The default basemap in the SWITRS GIS Map is Streets.

    List of Basemaps

    Basemap Description
    Imagery High-resolution aerial imagery; no labels.
    Imagery with Labels Same as Imagery, but includes labels of major streets, institutions, cities, and other points. Depending on how zoomed in or out you are on the map, the number and placement of labels that is displayed will vary.
    Streets (Default) Comprehensive map with street-level data. Depending on how zoomed in or out you are on the map, the basemap can include street names, water features, and other physical/political/economic points of interest such as parks, schools, and hospitals.
    Topographic Detailed topographic map that shows and labels political boundaries, water features, parks, landmarks, buildings, transportation, and other features.
    Terrain with Labels Shaded relief map that shows the physical changes to the landscape. This basemap also displays primary streets, county lines, and rivers.
    Light Gray Canvas Minimalist map with neutral colors and minimal labels for major streets and points of interest. This basemap is useful when you do not want detailed street information (as with Streets and OpenStreetMap) to be distracting.
    National Geographic Shaded relief map that uses National Geographic's cartographic and typographic design. This basemap shows administrative boundaries, protected areas, streets, railways, highways, water features, buildings, and landmarks.
    Oceans Map that displays and labels water body features , undersea features, and some derived depth values in meters.
    OpenStreetMap Collaborative map that displays data collected via the OpenStreetsMap project. For some locations, this layer may be more updated than other street basemaps.

    Location Search Bar

    To find a location on the map, enter an intersection or address, including the city and state in the Location Search Bar in the main toolbar; next, click the Search icon or hit enter on the keyboard, and the map will zoom to that location. If an exact location cannot be found, it will zoom to the nearest identifiable location such as the street or city.

    Similar to the Identify function, a white triangle will point to the address or intersection. A pop-up window will also display the address or location.


    3. Map

    Collisions that match the criteria in the SWITRS Panel and the turned on layers in Map Contents will be displayed in the Map. Use the zoom slider on the left of the map to zoom in and out; you can either click on the arrows on the top or bottom, or move the slider up and down. There is also a zoom-dependent scale bar on the bottom left of the map.


    4. Results

    Results Summary

    The Results box will show the summary status of the collisions that are displayed on the map. The box will state the number of collisions that have been mapped. Depending on the query different hyperlink functions will be shown in the box.

    Summary Statistics

    Clicking the Summary Statistics link in the Results box shows a pop-up chart and table summary of the mapped collisions. Users have the option to show summaries for All Mapped Collisions, only collisions in the Current Extent, or only Selected Collisions. In each case, the collision count and the tabs for Injury Severity, Collision Type, Primary Collision Factor, and Involved With update accordingly. The charts can be captured in a screenshot and the tables can be copied directly for quick visuals to include in a presentation or document.

    Refresh Collisions

    The number of collisions that can be displayed on the map at any given time is 1,000. Showing more than 1,000 would cause performance issues on the server and within users' web browsers. Of course, many queries will results in more than 1,000 records. In order to work within this restriction, there is a Refresh Collisions option, which is shown in the Results box when applicable. Clicking the link will give the option to Refresh by Current Extent or Refresh by Custom Drawing Extent.

    Refresh by Current Extent

    If you have zoomed in to the main area of interest, you can select Current Extent and only collisions within the map extent will be drawn. A green outline can be seen around the extent if you zoom out. If there are still too many collisions to be drawn, zoom in farther, and then Refresh Current Extent again.

    Custom Drawing Extent

    If you select the Custom Drawing Extent, you are given the option to draw a shape around the area of interest. This is a more precise option that can select collisions along a long corridor for example.

    Download Collisions

    Clicking the Download Collisions link in the Results box shows a pop-up window with several options.

    First, users should choose the extent of interest: All Mapped Collisions, Current Extent, or Selected Collisions (disabled if no collisions are selected).

    Next, the type of data file should be chosen: Collisions, Parties, or Victims. Typically, the collisions file will be of interest but you may also be interested in the Parties and/or Victims file.

    Finally, select from either a Comma Separated (CSV) Table file or a Google KML file (KML file only available for collisions). Click the Start Downloading button to download the chosen file.

    Note: Collisions, parties, and victims are related to each other hierarchically, with collisions being the parent or top entity. This means that collisions are first narrowed down by selected collision factors, next by party factors, and then finally by victim factors. For more information, go to the SWITRS Help page> Working with the relational database structure.

    Create Collision Diagram

    If you have spatially selected a subset of collisions, the Results box will show the option to Create Collision Diagram. This option will open a new browser window that attempts to show all the collisions with appropriate movement and collision type symbols in an interactive Google maps style. The user can then generate a single page diagram summary for printing. For more information on using the collision diagram tool, please refer to the separate help document Collision Diagram Tool User Guide.


    Frequently Asked Questions

    Querying SWITRS

    How can I make my map queries load faster?

    The SWITRS collision, party and victim files contain numerous fields for each collision. When querying statewide over multiple years, it takes a considerable amount of work for the server to find all matching crashes. It is recommended to restrict your query based on time, location, or collision factors as much as possible, especially for exploration purposes. There are approximately 200,000 fatal or injury records each year in SWITRS, so queries can become large very easily.

    How do I query collisions that occur outside of city limits in Unincorporated Areas?

    After you select a county in the query tool, the cities list will be populated with all the available cities as well as an UNINCORPORATED entry. Selecting UNINCORPORATED will show the proper results.

    Why do I see a different number of collision results for the same query in SWITRS Query & Map vs. SWITRS GIS Map?

    The SWITRS Query & Map includes all collisions regardless of whether they were geocoded or not. The SWITRS GIS Map only uses the data that was geocoded and could be mapped. Therefore, you will usually see a lower number of collisions in the SWITRS GIS Map than the SWITRS Query & Map tools. You can verify which collisions were not mapped in the SWITRS Query & Map tool by clicking on the 'List Unmapped Collisions' button above map on the summary page. You may also need to perform a 'Refresh Collisions' in the SWITRS GIS Map to show all the collisions in the current extent. A warning message in the application will state that only 1,000 collisions can be shown at once.

    Why do I see fewer collisions in my query than in my SWITRS data in our office?

    TIMS contains the fatal and injury collisions, but property damage only (PDO) collisions are not included. Many agencies have the property damage only collisions in their local datasets, so there will be a greater number of collisions. Not all records were able to be geocoded, either, so you may see fewer collisions in the map. Also, SWITRS GIS Map can only show 1,000 collisions at once. You need to perform a 'Refresh Collisions' to show all the collisions in the current extent.

    Data

    How do I find out what SWITRS fields and their values mean?

    The format of SWITRS data and descriptions of each of the data fields and their range of values are described in the SWITRS Codebook page.

    Can you give more information about the geocoded coordinates in the SWITRS data files?

    Approximately 90 percent of fatal and severe injury collisions have been geocoded through a process developed at SafeTREC. The Point_x and Point_y fields contain the longitude/latitude geocoded coordinate locations based on the 1984 World Geodetic System (WGS84). If the collision was unable to be geocoded, these two fields will remain blank. If you are downloading a subset of data, it will include all collisions that matched your criteria, but if you use the mapping tools only collisions that were geocoded will be displayed. Note that the longitude and latitude coordinates are different from the GPS coordinates that are also provided with some collision records from CHP.

    How do I display downloaded SWITRS datasets in other GIS software or applications?

    There are countless software and web applications for displaying data with XY coordinates. Each application will have its own steps, but it should be relatively straightforward. Here is the help library for displaying data in ArcGIS.

    Why are there fewer collisions in the most recent year of data available?

    It currently takes about 18 months for the California Highway Patrol (CHP) to input SWITRS collision data. For example, the final dataset for 2015 will likely not be available until summer 2017. On TIMS, we extract the most recent year of data available from the CHP on a quarterly basis. It will contain whatever records have already been input by CHP before that date. Therefore, until the most recent year is finalized, it will always show fewer collisions in TIMS.