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Introduction

Transferability is referred to the transferability of the 2001 Nationwide Household Travel Survey (NHTS) results to the regional or local level. Transferability is a methodology for using the NHTS data to estimate regional or local travel, including vehicle trips (VT), vehicle miles of travel (VMT), person trips (PT), and person miles of travel (PMT) by trip purposes. The resulting data can be used by transportation planners and analysts in their transportation planning process. The NHTS Transferability tool provides a map-based tool that enables users to download trip generation rate information for selected Census Tracts and Transportation Analysis Zones (TAZ).

Output Transferability Datasets

Output datasets are in Microsoft Excel spreadsheet and ESRI shape file formats (see examples for Tracts and TAZs). The spreadsheet files are in Microsoft Excel XML format compatible with Microsoft Office 2003 and above.

Transferability Tool Options

There are two tool options:

  1. Select by map with two options:
    1. Pre-rendered map of 48 states (faster, recommended)
    2. All states, dynamically rendered (slower)
  2. Select using menus of state and county

Map Navigation

Navigation tools with zoom and pan
Use the Zoom and Pan tools to identify the area that frames the Tracts or TAZs of interest.

Map contents with map layers
The pre-rendered map of 48 states contains two layers, one with Tracts and one with TAZs. Selections of both Census areas can be made with either map layer.

The dynamically rendered map offers more control of layer visibility.

Selecting Tracts and TAZs

Select by point, rectangle, line, polygon, or circle
Click Tasks, Select Tract or TAZ to open the Select Tool. Use the pull-down menu (<Choose layer>) to select Tract or TAZ. Selections are made by point, rectangle, line, polygon, or circle. Terminate the selection with a double-click. Use the Escape key to exit the Circle Tool.

You can create multiple selections of Tracts and TAZs. Also see Managing Selections.

Creating Datasets for Selected Tracts and TAZs

Create data tool
Click Tasks, Create Data for Selected Areas to open the Create Data Tool. Click the Create Data button to create the output datasets for the selected Tracts and TAZs.

Managing Selections

Results pane to manage selections
Selections are shown in the Results pane. Multiple selections of Tracts and TAZs can be made. Click the checkbox to turn on and off visibility of individual selections or Tracts/TAZs. To delete a selection, right-click and choose Delete from the menu.

Source Data

All data is at the Census tract level.

Household Characteristics

HHSIZE – Count of Household Members
HHVEHCNT – Count of Vehicles in Household
HHWGT – Number of Households:

Each tract contains household sizes, ranging from 1 to more than 5 persons, and household vehicle counts, from 0 to 4+, for a total of 25 different combinations per tract.  The HHWGT variable is the number of households for each Census tract-Household Size-Household Vehicle Count combination.  This number is derived from 2000 Census Summary File 3 (SF3) marginal totals by household size and Census Transportation Planning Package (CTPP) 2000 Part 1, Table 63 cross-tabulated data, which was obscured for confidentiality reasons.

MEDHHINC – The 2000 Census SF3 median household income for a given tract (irrespective of household size and vehicle count)

Daily Travel Statistics

PT – Daily Person Trips per Household
PMT – Daily Person Miles of Travel per Household
PMTNOAIR – Daily Non-Air Person Miles of Travel per Household
VT – Daily Vehicle Trips per Household
VMT – Daily Vehicle Miles of Travel per Household:

In the 2001 NHTS, a person trip is a trip by one or more persons in any mode of transportation.  Each person is considered as taking one person trip.  Similarly, a person mile of travel is a mile traveled by one or more persons.  A non-air person mile of travel simply excludes air travel.  A vehicle trip is a trip by a single privately owned vehicle (POV) regardless of the number of persons in the vehicle.  A vehicle mile of travel is a mile traveled in a private vehicle.  For example, if a household of 4 persons all took a 5-mile trip together in a POV, that household will have taken 4 person trips, 20 person miles of travel (of all which are non-air), 1 vehicle trip, and 5 vehicle miles of travel.

Estimates of these 5 variables were derived from 2000 Census SF3 data for each tract; inputs included number of workers per household (derived from household size for PT & VT, average per household for each tract for PMT & VMT), percent in a tract that use public transit to work, median household income for the tract, buying power (derived from median household income and ACCRA[1] 2001 cost-of-living data), the ACCRA cost of transportation index,  the employment rate for a given Census tract, the percent of household in a Census tract that own their home, Census division, MSA size, and life cycle information.

Person Trips by Purpose

PTPURP1 (Percent of PT for the purpose of Home-Based work)
PTPURP2 (Percent of PT for the purpose of Home-Based shopping)
PTPURP3 (Percent of PT for the purpose of Home-Based social/recreational)
PTPURP4 (Percent of PT for the purpose of Other Home-Based travel)
PTPURP5 (Percent of PT for the purpose of Non-Home-Based travel):

The PT by Purpose estimates were calculated using inputs detailed in the PT/PMT/VT/VMT section.  Other 2000 Census SF3 data was also used as inputs, including whether a tract had more than 50% of households defined as urban, the number of persons who used transit to work, number of adults per household (derived from household size), population density, and the ACCRA Cost-of-Living index by its self.

[1]ACCRA-the Council for Community and Economic Research located on the campus of George Mason University's Arlington Virginia campus.