Setting the Stage: Agency Restructures Routes with GIS Mapping Software

by Laura Lang (originally appeared in Transit California, July 1996)

Although it felt to planners like they "threw the bus system up in the air and rearranged it where the pieces fell," a route restructuring project by Orange County Transportation Authority (OCTA) last fall actually left little to chance.

In fact, using advanced software technology and recent statistics collected in-house and purchased from commercial vendors, it would seem OCTA's systemwide route changes were made in all the right places: ridership levels have been boosted 8 percent and service hours were reduced 5 percent.

"We started with a goal of identifying short- and long-term service improvement strategies, and found with the data and technology we had on hand, we were able to accomplish much more," said Nancy Michali, OCTA's manager of transportation planning.

OCTA's Bus System Improvement Project was the first systemwide review of the routes in 13 years. During that time, Orange County has increased its number of residents and businesses located in both urban regions and areas once considered rural. Passenger destinations, such as shopping malls and office parks, have changed in location, as have the neighborhoods with concentrations of likely transit riders.

To answer complex questions about why people would or would not use OCTA buses and make adjustments to routes that would encourage ridership, planners had to combine many kinds of data including transportation behaviors, street networks and paths, census demographics, land use, and business locations.

These were overlaid with electronic mapping software called a geographic information system, or GIS, to understand factors prohibiting use of the existing service. For instance, transit-dependent riders (such as residents with no car) were thought to be the most likely candidates to use public transit. However, if the bus stop or destination stop were too far (over 1/4 mile), they might choose not to use the OCTA bus.

With the GIS, planners studied the integrated data on color-coded maps and charts. "Putting data on the maps makes it easy to spot trends and ask the right questions," says Shirley Hsiao, OCTA senior transportation planner.

Using census demographics like income and car ownership, the agency determined which residents were most likely to use the bus system, which might use the bus system if it were more convenient to home or office, and which probably wouldn't use the system at all. By overlaying the bus stop locations and the street network with the GIS, they measured the system's accessibility—how easily people could walk to the bus stop and to their destinations—to each of these groups. If there were no direct connector streets to the route, requiring residents to walk farther than the 1/4 mile threshold, the stop was considered inaccessible to the neighborhood and residents, and the region was given a "low accessibility rating." If demographics were favorable and the route nearby, the region was color-coded as highly accessible.

Just by requesting different data for a map—such as viewing small business locations (under 100 employees) as opposed to large businesses—new trends were spotted and gauged for their overall impact to the system.

According to Hsiao, the GIS was used to created "buffer zones" around the bus stops, defining the study areas and calculating exactly how many potential riders (and which type of rider such as "transit-dependent" or "choice" riders) could access the system at its present location.

As the study progressed the GIS was used to move the routes around and find new routes that would increase ridership accessibility in the areas currently experiencing low transit coverage (but having a high number of potential riders), while minimally impacting areas with high accessibility. Applying the same tool to the employment database, new routes were drawn to increase pedestrian access at the major employment centers.

By moving the routes and stops on the electronic maps, new calculations were made automatically, so planners immediately knew whether they were impacting 40 or 400 riders with the new option. OCTA planners found they could be very specific on how many riders would be affected by route changes such as 600 out of a daily boarding of 60,000.

These figures were helpful in determining route changes, and they were later used when the agency justified the restructuring changes before the OCTA Board of Directors, says Michali. The route changes were made in October 1995 and have already resulted in dramatic system improvements, she says.

In addition to the internal OCTA study, the GIS was used to help the agency prepare environmental clearance paperwork in accordance with the California Environmental Quality Act (CEQA). "The analysis software helped us to present a very focused environmental analysis and keep study preparation costs down," Michali says.

According to Hsiao, the GIS and County-wide data will be used on an ongoing basis to further improve transit services, tweaking routes when new factors, like a new mall opening, justify changes.

The study sets the stage for how agencies like OCTA can monitor shifting populations and expanding employment centers—just two factors that can render routes obsolete. Says Michali: "As we try to be more customer oriented, GIS is a great tool for zeroing in on who is our customer on a route-by-route and segment-by-segment basis.

"With a thinning staff, we need technology to supplement the number-crunching that the staff once did and make sure our service is reaching all of our potential riders, especially those most reliant on public transit."