Introduction

The SWITRS Query & Map application is a tool for accessing and mapping collision data from the California Statewide Integrated Traffic Records System (SWITRS). To use this tool, click on SWITRS Query & Map from the Tools dropdown menu. This user guide explains how the three steps in the tool works, as well as additional tips.


1. Select Date and Location

The first step allows you to select the year(s) and location(s) that you are interested in for collision data.

Select Date

Choose your timeframe. You can either type the start and end dates directly into the fields, or select them from the calendar pop-up menu.

Note: The default timeframe on the tool is for the most recent complete year of SWITRS data available. There may be provisional data for the next year also available.

Select Location

After selecting your timeframe, you can next select the county of interest. You will next have the option to select either the Cit(ies) or State Highway(s) that are of interest within that county.

City

If you choose City, the city box will populate with all the cities in that county, as well as an option to choose the unincorporated areas.

State Highway

If you are interested in a particular state route, select State Highway, and the highways in your county will populate. From here, you can also choose the direction of the highway.

After you have selected the county, city, or highway of interest, click on Select Factors to continue.

Tip: How to select multiple cities or highways:
  • Windows: Ctrl + Click
  • Mac OS: ⌘ + Click

2. Select Factors

In Step 2, you can choose among three different types of factors to help narrow down the collisions: collision factors, party factors, or victim factors.

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.

Collision Factors

Collisions factors are the SWITRS variables that directly relate to collisions. (Note: you do not have to select a collision, party, or victim factor to continue on to the Summary page.) When you select or check a factor that you are interested in, that factor's values will populate at the top of the factor options. You can then select the values that pertain to your project.

Tip: At the top right of each factor tab, there are buttons to Check All Factors, Uncheck All Factors, or Remove the Selected Factor. You can also remove a previously selected factor through the Current Selection blue box on the right of the screen. Simply hover over the factor, and click on the X to the left of each factor.

Party Factors

Every collision has one or more parties involved. If you had previously selected a collision factor, these collisions will then be further refined by party factor.

Victim Factors

A victim is any person that was involved in the collision; he/she is included in one of the involved parties. There can be more than one victim in each party. Select the victim factors and its associated values that you are interested in for your project.

When you have finished selecting factors, click Continue.


3. Results

The Results page is the final screen. Remember that you can go back and change/remove any of the selected factors by clicking Change Factors

Results Summary

In the top half of the page, you will see Results Summary for the collisions that you have queried. The Selected Factors are shown in a collapsible window. This section also displays the total number of collisions that match your query, as well as the number and percentage of collisions by five commonly looked at collision factors. Note that these summary results are showing you only collisions data. You can quickly copy and paste the information from these tables into another document.

In addition, below the Results Summary are graphs and charts that illustrate the five most commonly looked at factors for each category (collision, party, and victim). You can select which category to look at from the bar highlighted in red. For example, below is a pie graph that depicts the number of collisions by collision severity.

Export Data

You can also print and export the graphs and tables in various formats by clicking on the export icons.

Download Data

There are three types of data that you can download from this page: Collisions, Parties, or Victims data. Click on Download in the results summary.

Collision Data

Download the collisions data if you are interested in the data at the top collisions level. Once it's downloaded, open the spreadsheet. Notice that there are additional fields in the spreadsheet that weren't shown on the SWITRS Query & Map tool; all of these fields are from the original SWITRS database. Use the SWITRS Help page to learn about the fields, their descriptions, and possible values.

Each collision has a geocoded latitude and longitude coordinate in the POINT_X and POINT_Y fields. These fields are used to map the collisions. Some collisions have a 0 in these two fields, indicating that these collisions could not be mapped. For more information on why a collision could not be mapped, see FAQs > Data. The data you now have in this spreadsheet can next be used in the Benefit/ Cost Calculator tool, or another tool of your choice.

Save Query

In addition to downloading the data, you may also choose to save your query. After a query is saved, you can then review or make changes to any parameters or factors at a later date. To save, click on Save Result in the results summary and type in a title. Click on Save, and a window should next pop up notifying you that your query was successfully saved. To view your saved queries, click on Load at the top right of the page; this feature will be further explained below.

Query Options

The query options listed in the top-right section of the header allow you to perform different tasks associated with queries.

New Query

Click on New Query to start over from the beginning of the tool.

Load CASE IDs

You can also Query by CASEIDS by inputting the ID of each collision in SWITRS. Option 1 allows you to type in the CaseIDs. Make sure to separate them by commas or a space. In Option 2, you can reference a CSV file that contains a list of CaseIDs; this can be a Collision file that you have previously downloaded.

Saved Queries

The Load page populates with all of the queries that have been saved using the Save Result feature. The table shows the date the query was saved, how many results match that query, and other basic information on the query. Click on a query to highlight it, and then you can choose to either Load it back into the SWITRS Query & Map tool or Delete the query.

Results Map

Clicking on Map will display all the collisions that could be geocoded and mapped. The number and percentage of the collisions that are mapped are stated at the top of this section; 4 of 4, 100% of collisions are mapped.

If you are interested in the collisions that were not mapped, click on List Unmapped Collisions, and a page will pop up to show some basic information on these collisions.

Note: For more information on why a collision could not be mapped, see FAQ > Data.

Map Features

Cluster vs. Heatmap

By default, the collisions should be displayed as clusters. You can see that markers' colors and sizes are dependent on the number of collisions. If you click on a marker for a cluster, it will list the collisions at that cluster by intersection. Click Zoom to zoom into the area where that cluster of collisions occurred.

Basic Collision Information

Click on a marker for a collision to bring up more information about that specific collision.

Collision Details Page

To learn more about a collision, click on its marker and then the "here" in Click here for street view profile. This opens a Collision Details page for that collision, where you can interact with the Google Maps street view to look at the intersection or area where the collision occurred. From this profile page, you can also see that this collision is a pedestrian collision, that the right of way was the primary collision factor, and other basic useful information.


Frequently Asked Questions

Mapping 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. If you subsequently map those results, the performance will also be slower to accommodate so many records. 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.

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 Results Map.

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.