Forecasting Balanced Highway Volumes Using Modeling Packages and Spreadsheets

Abstract

In many applications, particularly upon requests from highway engineering and design departments, transportation planners need to forecast link volumes of a particular highway. That usually includes turning movements at various interchanges and intersections. It is not unusual, for certain links in a high-growth area, that one or more of the forecast volumes are less than the present ones. A probable reason is that some of the base year volumes at that location are underestimated, or, generally, the base year model volumes are not very similar to the base year traffic counts. Attempts by practitioners to “factor up” those low volumes might result in an unbalanced forecast. The question of producing forecasts that are consistent among themselves and compatible with the base year counts using modeling packages and spreadsheet techniques is addressed. The latter is important particularly for transportation planners who do not have packages directly available to them. For planners who have packages, however, spreadsheet techniques could be beneficial when a quick response for several scenarios is needed. Simple techniques using a spreadsheet with or without transportation modeling software are described and applied to an example from the city of Niagara Falls, Canada. The results are compared with a more sophisticated technique. It is argued that the simple techniques can provide good approximations to the more sophisticated one in some applications.