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Seasonality of Transportation Data

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TABLE 1 - Advantages and Disadvantages of Continuous Measurement for the Transportation Community

TABLE 2 - U.S. Census Variables Used in Transportation Planning and Programming Processes


TABLE 1 Advantages and Disadvantages of Continuous Measurement for the Transportation Community

Advantages

  • Agencies will not have to use twelve-year-old data in their planning activities (decennial census + at least two year data release time)
  • Can argue that larger areas (with larger data and planning needs) will receive acceptable data every year or three years (still with two-year lag, possibly)
  • Seasonal data: capture more bike and walk trips; capture different times leaving for work

Disadvantages

  • DISCLOSURE-getting enough data for transportation uses
    • Huge concern that individuals aren't identified from released data
    • We may want mode by travel time by race by people who go from A to B but because some modes are infrequently used and some races are infrequent, this may lead to specific individuals
    • In general, census will release statewide data with 75 observations per tabulated "cell"
    • Census Transportation Planning Package (CTPP), closer to 30, some arrangements of five observations representing 30 people
    • Race by mode by place of work... getting even five observations is difficult with 17% sample; now 3% sample
    • Regression requires similar "cells"
    • Travel time = a + b1*income +b2*place of work requires (75) in each income/place combination
  • Aggregation of five-year data for some areas, shorter periods for some sub areas-within the same metropolitan statistical area
  • Error may propagate over five years
  • One planning agency uses 2003-2007 data; another using 2005-2009 data may lead to different baselines
  • Worries about continuous congressional funding
  • Unexpected costs per completed interview may lead to longer data accumulation periods or only voluntary data. Currently the Census Bureau is "experimenting" with collecting only voluntary data (mail sample only, no follow-up phone or in-person interviews) (Quesinberry, 2003).

TABLE 2 U.S. Census Variables Used in Transportation Planning and Programming Processes (Table is modified from (Christopher, Murakami, Riklin, and Srinivasan, 2003)

Journey to Work and Mobility Questions

Demographic Variables

Place of Work

Travel Mode to Work

Vehicle Occupancy

Travel Time to Work

Time Left for Work (or Time Arrived)

Number of Vehicles in Household

Disability status affecting employment

Usual Hours Worked Per Week

Actual Hours Worked Last Week

Vehicles Available

Sex

Age

Race

National origin

Citizenship

Education

Building Type

Employment Status

Employer Industry

Employee Occupation

Worker Earnings

Household Income

Household Size

Household Type

Geographic Mobility

Language

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Updated: 04/28/2011
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