Using GIS for Accident Analysis


Los Angeles County Metropolitan Transportation Authority Automates Bus Safety

Los Angeles County Metropolitan Transportation Authority (Metro) is the California regional transportation planning agency and public transportation operating agency for the County of Los Angeles. Metro operates the third largest public transportation system in the United States and is responsible for serving nearly one-third of California residents. That includes 9.6 million people within its 1,433-square-mile service area!

Metro’s bus infrastructure consists of 15,967 bus stops, 183 bus routes, and a bus fleet of 2,228. For the month of March 2012 total bus boardings were estimated at 30,271,955. Given the vast geographic area and large number of riders, ensuring public safety and minimizing accidents is one of Metro’s main concerns.

LA Metro 740 Rapid Bus

Automatic Analysis of Accident Data

Metro’s Service Performance Analysis Division is responsible for assuring the highest level of safety for its bus riders and the general public. Through the analysis of bus accident history, Metro is able to identify significant safety issues and determine areas where measures can be taken to reduce the number of incidents.

Metro derives its bus accident data from Transit Safe and its Vehicle Accident Management System (VAMS). Formerly, its staff processed accident data monthly using SPSS statistics modules. They used ArcGIS to geocode accidents and create map for each of the eleven bus-operating divisions. The maps were then shared out via the Metro Intranet. But this was a manual process.

Recently, with the support of Esri partner Integrated Spatial Solutions, Incorporated (ISSI), Metro automated its tools for processing and analyzing accident data. It also developed a user-friendly interface for displaying accident information.

Accident Analysis Web Application

Connecting Oracle with GIS

The new toolset for processing accident data is written in VB.NET and runs with ArcGIS 10 and ArcSDE. The geodatabase connects to an Oracle database running on an AIX machine. The interface consists of a menu with month and date selection and four buttons to allow the user to prepare accident data for geocoding, point generation, hotspot creation, and statistic generation. Metro and ISSI divided the process into four steps so that the user may validate output after each phase.

Four Steps to Data Analysis

One tool prepares data for geocoding tool. It pulls raw accident data for the selected month from Transit Safe and generates tables for geocoding. The geocoding process uses Thomas Bros street data and is based on addresses since Transit Safe does not currently collect x,y values when an accident occurs. The points are then generated for the addresses, and a single record is created for each accident. These records are appended to the Accident feature class which contains historic Metro accident occurrences that date back to November 2007.

Next, hotspots are generated every month for a 13 month period for all districts. These hotspots indicate areas where a large number of accidents may have occurred and allow Metro to quickly analyze the problem and remedy the situation. These hotspots are integrated into an historical database of hotspots dating back to November 2007.

Accident Analysis Hardcopy Map Output

The statistics tool allows the user to choose two months of accidents for comparison. It displays the total number of accidents as well as accidents per division. These statistics can be useful in displaying a decrease in accidents over a period of time.

The web-based mapping application is written to work with ArcGIS Server 10 and ArcSDE connecting to an Oracle database on an AIX server customized using VB.NET. The application displays individual accidents and system-wide hotspot locations for the past 13 months along with roads for reference. The application contains a custom interface containing dropdown boxes for month/year input and Metro division as well as out-of-the box ArcGIS Server tools. There is also a print function that generates a B-Sized landscape PDF file using a custom map template. C# is utilized on the server side in order to generate high quality PDF images for the user.

Looking Ahead

The new processing tools and web-based application are a huge improvement over the previous process.

“The Accident Analysis tools have proven to be both a time-saving and accuracy- ensuring application,” said Jeffrey Neely, Sr. Administrative Analyst for Metro’s Service Performance Analysis Division.

With the old process, producing accident maps took about four to five days. The process was reduced to one to two days with the new process.

“With regard to accuracy, the maps are created programmatically,” Neely said. “The opportunity for error has been greatly reduced.”

The new tools and web interface are an improvement over Metro’s previous process. They provide processing, analysis, and graphic display of complex data in a more readable format. These new tools assist Metro in providing the highest level of safety for its bus riders and public in general.


For more information, please contact Julie Henry, ISSI, jhenry@issi-gis.com.