Network Attributes Calculator
Corresponding Author: Vipul Modi, Citilabs Inc.
Presented By: Vipul Modi, Citilabs
Abstract
Travel demand model network attributes form the basis of any transportation planning analysis, of these roadway capacities and speeds are the most critical attributes that are used. While there are conventional methods that one can use to determine the capacities and speeds, the move towards finer operational level network detail and availability of new data sources make traditional methods less tractable. Rather than using traditional methods such as lookup tables or direct coding of these values on links, The Ohio Department of Transportation developed an application that computes these attributes from observed link attributes over 25 years ago largely using the 1985 Highway Capacity Manual (HCM). These tools were subsequently updated for the 1994 and 2000 HCM’s. Recently an update was completed based upon the 2010 HCM which included significant methodological enhancements as well as an update in its implementation language. These tools compute capacities for interrupted and uninterrupted facilities in urban and rural areas, account for cross street characteristics when determining capacities, the actual location of the next downstream controlled intersection even if not on the subject link itself, integrate signalized, two-way stop, four-way stop and new roundabout methodologies as well as capacity reductions for weaving segments on freeways and more. Further, these tools also automatically create junction and turn penalty files based on network link attributes. With use of these files, explicit dynamic intersection delays based upon HCM procedures can be applied during highway assignment rather than using capacities with VDF functions without the need to maintain this information separately. This paper will present all the methodologies used to create such tools and the software implementation.