As the Metropolitan Planning Organization (MPO) for the southern New Jersey region, encompassing Atlantic, Cape May, Cumberland, and Salem counties, one of the South Jersey Transportation Planning Organization’s (SJTPO’s) major responsibilities is the adoption of long-range regional plans to guide transportation investment decisions for at least a 20-year horizon period, if not longer. As such, the preparation of this plan, (as well as much of the other work conducted by an MPO), requires the use of a sophisticated tool to predict future traffic needs and travel conditions. The specific tool utilized by many MPOs is the regional travel demand model. Utilized by many MPOs, these computer-based tools are rather complex, using numerous inputs such as demographic information (e.g. population and employment) and the transportation network (e.g. roads and transit lines) to simulate these future conditions. Another major application of these travel demand models is to demonstrate conformity of future transportation investments with air quality emissions levels as specified in the State Implementation Plan (SIP) and mandated by the 1990 Federal Clean Air Act Amendments.

Although the SJTPO currently has a regional transportation model, known as The South Jersey Travel Demand Model (SJTDM), it was originally developed in the late 1990s and some of the original software programs used to run the model have become obsolete. One of the major tasks outlined in the FY 2011-2012 Unified Planning Work Program (UPWP) are improvements to this model. These improvements will include the migration of the SJTDM from its current platform of TP Plus to a more state-of-the-art modeling package (see below), as well as enhancement of the various modules, improved calibration and validation, and training culminating with an updated version of the User’s Guide.

Here are some of the major characteristics of the current SJTDM:

Platform: The SJTDM currently operates under the standard 4-step modeling regime, consisting of Trip Generation, Trip Distribution, Mode Share, and Travel Assignment. The latest version operates under the TP+/MINUTP platform with a few standalone FORTRAN and CLIPPER programs. Over the course of the next year, the model will be migrated to the CUBE Base/ Voyager software package.

Zonal System: There are over 1,900 traffic analysis zones (TAZs) in the SJTDM. The TAZs are loosely based on 1990 Census Tracts. Of these, 1,400 zones are internal, meaning they are completely inside the SJTPO region. The model also includes zones from the Delaware Valley Regional Planning Commission (DVRPC) model, as there is a high level of trip interaction between the SJTPO region and that of the DVRPC.

Highway Network: The existing road system that is represented in the SJTDM is known as a highway network. The highway network includes most of the major arterials in the region down to the 500 level. As with the zonal system, the highway network includes facilities in the DVRPC region.

Transit Network: Similar to the highway network, the SJTDM also includes a transit network. The transit network includes New Jersey Transit’s rail and bus network, as well as some casino shuttles and local jitney-type services.

Trip Purposes: The existing SJTDM covers a variety of trip purposes, including recreational trips-(i.e., casino and shore trips), as well as non-recreational trips, such as commuter and work trips, shopping trips, school trips, and truck and commercial trips.

Time Periods: Trips are assigned to the highway network in four different periods. They are as follows: AM Peak (6 AM - 9 AM), midday (9 AM - 3 PM), PM peak (3 PM - 7 PM), and night (12 AM - 6 AM and 7 PM - 12 AM). Transit trips are assigned in a slightly different manner, representing three different periods: Winter weekday peak, winter weekday off-peak, and summer weekday off-peak.

Future plans include expanding the SJTDM to report winter and summer weekend trips.

Files for Download:

SJTDM Flow Chart (pdf: 7,633 KB)