Traffic impact analysis by using geographic information system technology

Abstract

Several software tools are available to help the planner or engineer forecast the traffic impacts of site developments that are too small to effectively use transportation modeling software. Using these tools can provide numerous time-saving advantages. The tools include trip generation software that has built-in trip rates taken from the Institute of Transportation Engineers trip generation manual and manual path-encoding traffic impact software that will identify turn movements and link volumes (as well as intersection levels of service) given certain inputs. Manual path-encoding software such as TRAFFIX requires manually creating a network of project zones, critical intersections, and connecting road segments; inputting existing count data and trip generation information; manually describing the paths that traffic takes to get from a development to a gateway (trip assignment); and inputting the percentage of trips that go to each gateway from a development (trip distribution). Once these inputs have been made, traffic volumes that result from the developments are automatically applied to the intersections. Many of the manual path-encoding software packages will include intersection capacity analysis capabilities. A major benefit of manual path-encoding software is that different land use alternatives can be analyzed quickly. The drawback of these software packages is the extensive manual input required for even small networks. Described in this paper is a site impact tool based on geographic information system (GIS) technology that works on the same premise as the manual path-encoding tools. The major difference is that this approach makes heavy use of the network analysis and map manipulation tools of GIS to significantly enhance the process of doing traffic site impact analysis. An actual application is presented.