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Automating Road System Maps
By Keith Mann, Esri Industry Solutions Government Team

County improves quality control and traffic safety with ArcGIS Server

Editor's note: Maintaining safe and drivable public roadways in the unincorporated areas of San Bernardino County, the largest county in the United States, is a formidable task. The county is automating its traffic safety system by moving the county-maintained road data into the GIS database, using an ArcGIS Server Web mapping application that allows the user to inspect road features, and using a custom maintenance shell accessed from the Web mapping application for updating road features.

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The original Traffic Road Book contained black-and-white map pages based on manually drafted Mylar sheets.

The Department of Public Works—Transportation/Traffic Division is responsible for maintaining more than 2,600 miles of road in a county that covers more than 20,000 square miles. In addition, the Traffic Division is required to annually provide the Controller for the State of California, through the State Department of Transportation, the total road mileage for the County Maintained Road System (CMRS) per section 2121 of the California Street and Highway Code.

The department has developed the Traffic Safety Management System (TSMS) and obtained grants from California State Office of Traffic Safety (OTS) to assist in defining high accident locations through traffic engineering investigation. TSMS includes traffic data information such as Average Daily Traffic (ADT), speed zones, and more than 350,000 traffic control devices. Key components of the TSMS are the Traffic Road Book and the County Road System Maps.

Working with a Nonautomated System

The original County Road System Maps are a set of detailed maps depicting all the roads in the county. Each map page includes other features such as Local Agency Formation Commission (LAFCO) boundaries. Each map was drawn on an individual sheet of polyester film called Mylar. The county acquired the Mylar sheets from the California Department of Transportation in the early 1970s. When the road system changed because a new road was constructed or existing roads were annexed, the Mylar sheets had to be updated using a CAD system or by hand.

In the original Traffic Road Book, information about county-maintained roads is recorded as road sequence descriptions and stored in an IBM DB2 database maintained by the Traffic Division. A printout of all the road sequence description records is bound into an eight-inch-thick volume and distributed with any changes or updates. County Road System Maps sets are still in wide use today. Approximately 200 copies are distributed throughout San Bernardino County and are used by traffic safety analysts, road designers, surveyors, contracts personnel, flood control engineers, and planners and at the front counters of various departments serving the public and other government agencies such as the California Department of Transportation. The County Road System Maps are also sold to private entities, such as developers, and other jurisdictions and agencies.

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Map pages for the new Traffic Road Book are in full color. County-maintained roads are based on the Traffic Maintained Road feature class and are shown in orange.

According to Mary Anne Causey of the Traffic Division, the County Road System Maps are popular among staff members from different departments, but the process of manually editing the map book and keeping the road sequence description database up to date means that revised versions of the Traffic Road Book are not published very often. "Our current system for maintaining the original County Road System Maps doesn't allow us to automate updating procedures," said Causey. "It is a strictly manual effort to keep the resources in sync and up to date."

Traffic safety analysts use the County Road System Maps to prepare the traffic collision diagrams for the road or intersection involved. However, Traffic Division chief Jacob Babico explained that creating automated collision diagrams can be a labor-intensive process when using the antiquated County Road System Maps to develop the report. "First of all, you cannot simply extract a diagram for a particular road sequence from the map book," said Babico. "Plotting all the accidents that have occurred at each intersection along a road with high traffic volume must be done by hand."

Envisioning a New Automated System

"What we need is an integrated system," said Babico. "We need to automate TSMS by linking all of the necessary databases in order to supply the most reliable and accurate information about our roadways. The new system would help us compose maps for Traffic Engineering Investigation (TEI) and other reports but would also give us the ability to analyze traffic accidents and road safety in the context of other information."

Babico presented his idea of an integrated system to the Information Systems Department (ISD), which provides professional IT and communications services to all county departments. He eventually spoke with Mike Cohen, team leader for the Application Development Division (ADD) GIS. "The timing of Jacob's proposal created a special challenge for us because we were in the middle of one of our biggest projects, namely converting all of the county's GIS data to an ArcSDE Oracle database," remembered Cohen. "We agreed that the first step in modernizing the County Road System Maps was to get the county-maintained road data into the GIS database."

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The Limit Description Conversion Workflow is a combination of automated processes and visual inspection of the data. The road limit descriptions in the DB2 database are parsed, then geocoded with the Traffic Maintained Road feature class in the ArcSDE Oracle database. Matched records are visually assessed for quality using a customized ArcGIS Server Web application. Edits are performed using a custom editing shell written for ArcMap.

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