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Perspectives of Person-Based Travel Surveys

Description:

Problem: Many travel surveys are designed to collect data on trip making from all household members. The 2009 NHTS considers households valid only when trip reports for fifty percent of the adult members are provided, but the 2016 NHTS requires 100%-member participation in order to be considered a complete. These completion rules have an effect on response since 25% or more of the households which are amenable to participation do not become part of the final database because not all, or not enough, household members complete the trip reports. This is an especially significant loss in the fidelity of travel information collected. These “incomplete” households still contain potentially valid trip making, excluded only due to the incompleteness of a particular household.

As the industry considers the exclusion of these “incomplete” households, and what to do with a set of trips collected but excluded due to household incompleteness, several questions are worth considering: 1) can we select one or more persons in each household to complete the travel information and then replicate or synthesize the remaining “unreported” person trips and distance to estimate the total trips and distance per household for the major modes; 2)What kind of selection processes (sample schemes) would work best; 3) Can a survey focused on collecting person level trip making without consideration of collecting a more complete picture of the travel at the household level provide stable long-term relationships between land use, socio-economic characteristics, and travel; 4) Can person-based travel survey be used to develop and forecast long-term trends; 5) what characteristics and variables are the most stable in the long-term; 6) can households be synthesized from person-based travel surveys?

Objective:

Objectives: As response rates have been falling, we need to analyze the places in a multi-stage survey where we have been consistently losing respondents along the way. In the first stage of the traditional household travel survey, the household is contacted and information about the members of the household, such as age, sex, relationship, worker status, is obtained. In the second stage of the survey we send a diary for each household member to use to track his or her travel on the assigned travel day, and call and collect the information about the travel. We often lose respondents at this second stage, either as outright refusals, non-contacts (generally passive refusals), and because some but not enough of the people have completed the travel portion of the survey.

As part of this research proposal, the second-stage sample of people within the household would be accomplished by randomly selecting one or more adults in each household. The objective would include developing selection criteria that would replicate the data collected from a fully reporting household for the key travel demand variables, i.e. person trips and vehicle trips per household by mode and purpose.

Some of the issues in developing a sample scheme for selecting the person or persons in each household would include:

● How does household composition (life cycle) effect the probability of selection? A person with the same age and sex living in either a dual-earner household with no children or a dual-earner household with two children have different amounts and types of trips.

● How does the number of vehicles per driver or worker effect the probability of selection? A two worker household with two vehicles or more will have different types and amounts of travel than a two worker family with one car, or no vehicles at all. Important variables, such as auto occupancy, transit use, and time of day of travel could be different in households with different levels of vehicle ownership.

● How do the household composition and vehicle availability interact? Do two earner households with no children and one vehicle require different probability of selection than two earner households with two cars, or with one car and two children?

● Are the land use, socioeconomic, and travel relationships developed from these “synthesized” households statistically significant or statistically different from those relationships derived from more fully observed households?

One approach to be considered is one in which there is a side by side field test with either the 50 percent rule of household completion or a rule requiring all household members to be accounted for on one side, and a sample person selection process using the scheme developed in stage one on the other.

The major questions from the field test would be:

● Are resources saved and how big is the savings?

● Does the lower burden per household increase response (lower loss at the second stage?)

● Are the data improved (biases reduced, etc) by targeting a specific person in each household rather than allowing whoever can to complete (especially in larger households)?

● How does proxy reports affect the data? Are there more or less proxy reports?

● How well does this method represent non-vehicle travel?

● Can this method fully represent the within household dynamics researchers require?

Implementation:

Implementation: The State DOTS are currently spending time and resources collecting large-scale travel surveys as inputs to statewide travel forecasting models. This proposed technique could save tremendous time and resources for the States and MPOs that conduct travel surveys.

Sponsoring Committee:ABJ40, Travel Survey Methods
Source Info:Updated by Mario Cools, Chris Hiebert, Chris Coy, Anurag Komanduri
Date Posted:08/29/2017
Date Modified:04/20/2018
Index Terms:Travel surveys, Data collection, Data quality, Households,
Cosponsoring Committees: 
Subjects    
Data and Information Technology
Planning and Forecasting
Transportation (General)

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