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 (new) from the Tools dropdown menu. 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. Toolbar

  2. The Map SWITRS panel, tools, map contents, basemaps, and location search bar are located in the horizontal bar across the top of the map. All the functions to query SWITRS can be found by clicking Map SWITRS.
  3. Navigation Toolbar

  4. The navigation toolbar is located towards the top left. It provides several options for navigating 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. 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.

1. Toolbar - Map SWITRS

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. Factors that have been selected will appear in the middle of the screen. When a filter is hovered over, an x button will appear which will delete that specific filter when pressed.

Refer to the codebook 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

Choosing

  • State Highway
  • (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. Choosing None will only show collisions not associated with the state highway system.

    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 bottom right of the dialog. To navigate through the different collisions, click on the small arrows. There are also two options across the bottom of the pop-up.

    • Zoom to: Zooms your map closer into that collision on the map.
    • 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.

    Other toolbar features

    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 drawing tool allows you to draw a shape around the collisions that you want to select. Choose either the Point, Multi-Points, Polyline, Rect, Polygon, or Free Hand 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. Choose a shape. Hovering over a shape button provides a description (e.g. Point, Multiple Points, Line, etc.).
    3. Follow the on-screen instructions on the map.

    Select by Buffer: Polyline
    25 ft

    Select by Buffer: Multiple Points
    75 ft

    Create Collision Diagram

    Once 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.

    Download Collisions

    The Download Collisions tool shows a pop-up window with several options.

    First, users should choose the extent of interest: All Mapped Collisions 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.

    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.

    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.

    Once you have selected a distance and pressed calculate, the top 10 intersections will be displayed.

    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.

    Collision Summary

    Select the Collision Summary tool from the tools dropdown to view an in-depth summary of the mapped collisions. Users can choose to sort the collision counts by collision factors, injury trends, or killed/injured victim.

    Collision Factors

    When collision factors is selected, users can sort by 3 different variable types: Collision Variable, Party Variable, or Victime Variable. Then, users can choose various subtypes based on the collision variable selected. The hamburger icon on the right allows users to print or download the chart.

    Injury Trends

    The injury trends option displays the number of collision counts per month and year.

    Killed/Injured Victim Summary

    The killed/injured victims option sorts the collision counts by gender.

    Display Options

    There are several different ways to symbolize collisions. Display options can be changed by clicking Options in the toolbar. A pop-up will then appear on the left side of the screen

    Display

    Symbols

    You can change the size of the symbols and choose to display the collisions as symbols stratified by Collision Severity, Type of Collision, or Motor Vehicle Involved With. After selecting a type of stratification, you can then choose to turn on/off colors for each value.

    Layers

    Layers 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.

    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. Vector Basemaps have the best performance on machines with newer hardware. Please disable the Use Vector Basemap option if your computer has performance issues. Vector Basemaps can be displayed in Chrome, Firefox, and Safari.

    List of Basemaps

    Basemap Description Vector Basemap Available
    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. Yes
    Satellite High-resolution aerial imagery; no labels. No
    Hybrid 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. No
    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. No
    Topographic Detailed topographic map that shows and labels political boundaries, water features, parks, landmarks, buildings, transportation, and other features. Yes
    Light Gray Minimalist map with light 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. Yes
    Dark Gray Minimalist map with dark 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. Yes
    OpenStreetMap Collaborative map that displays data collected via the OpenStreetsMap project. For some locations, this layer may be more updated than other street basemaps. No
    Streets Night Detailed vector basemap that displays a custom "night time" street map style. When the Use Vector Basemap option is deselected, it becomes the dark gray basemap. Yes
    Streets Relief Shaded relief map that shows highways, major roads, minor roads, railways, water features, cities, parks, landmarks, building footprints, and administrative boundaries. When the Use Vector Basemap option is deselected, it becomes the streets basemap. Yes
    Streets Navigation Comprehensive map with a custom navigation map style that is designed for use during the day in mobile devices. When the Use Vector Basemap option is deselected, it becomes the streets basemap. Yes

    Location Search Bar

    To find a location on the map, enter an intersection or address, including the city and state into the Location Search Bar in right of 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.

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

    Side Menu

    Pressing the icon towards the left of the toolbar will display a side menu that contains the same options.


    2. Navigation Tools

    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. Navigation functions include:

    • Zoom in: Zoom in to queried location.
    • Zoom out: Zoom out from queried location.
    • Zoom to full extent: Gives you view of the world map.
    • Zoom to current location: Zooms in to your current location.


    3. Map

    Collisions that match the criteria in the SWITRS Panel and the turned on layers in Layers will be displayed in 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.


    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 5,000 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 5,000 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.