A Guidebook for Using American Community Survey Data for Transportation Planning (2007) / Chapter Skim
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Pages 117-130
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From page 117... ...
Figure 7.1 shows transit usage by income and race.76 Figure 7.2 is a thematic map showing 117 C H A P T E R 7 Transportation Market Analyses Using ACS Data 75 R Cervero, 1994, "Use of Census Data for Transit, Multimodal, and Small-Area Analyses." Transportation Research Board, Decennial Census Data for Transportation Planning, Conference Proceedings 4, Irvine, California, March 13-16, 1994.
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From page 118... ...
25 20 15 10 5 0 Percent Income Black Hispanic Asian White <5k 5-10k 10-15k 15-20k 20-25k 25-30k 30-40k 40-50k 50-60k 60-70k 70k+ Figure 7.1. Transit use to work in metropolitan areas, by race, ethnicity, and household income, 1990.
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From page 119... ...
The goal of this analysis strategy is to ascertain the differential impact of moving from census to ACS data on this given measure of importance to public policy; transportation; and municipal, community, and regional planning personnel. In this case study exercise, begin by treating both the ACS estimates and the census counts as point estimates, without regard to the ACS sampling error.
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From page 120... ...
At the PUMA level, the following conclusions can be made: • The first column of values shows that, on average, roughly 35 percent (ID value at 35.1) of all blacks would have to move from their current PUMA residence in order to be proportionally 120 A Guidebook for Using American Community Survey Data for Transportation Planning
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From page 121... ...
Transportation Market Analyses Using ACS Data 121 PUMA Tract Block Group Block Data Source Census 2000 ACS 1999-2001 Net Difference % Difference W/B 35.1 35.3 0.2 0.6 W/H 17.5 18.0 0.5 3.0 B/H 32.9 33.0 0.1 0.4 W/B 62.7 63.0 0.3 0.5 W/H 31.5 32.5 1.1 3.3 B/H 53.5 55.5 2.0 3.7 W/B 66.0 66.2 0.2 0.3 TAZ W/H 35.0 36.9 1.9 5.1 B/H 56.6 58.7 2.1 3.6 W/H 33.2 -- -W/B 64.5 -- -W/B 70.4 -- -W/H 41.5 -- -B/H 60.2 -- -B/H 54.8 -- -N 13 279 777 689 20,136 * Source: Census 2000 & American Community Survey, 1999-2001 (weighted)
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From page 122... ...
theoretically indicates the extent to which the sub-population groups of interest are evenly distributed and, if not, identifies the proportion of either group that would 122 A Guidebook for Using American Community Survey Data for Transportation Planning 79 It should be noted that the ACS data used in this analysis are custom tables prepared from 1999-2001 average data, where the sampling rate has been increased so that the three-year data would possess the level of accuracy obtained from five-year data under normal sampling rates. Thus, when analysts compute the ID at the tract or TAZ level, they should be aware that multiple-year data are needed.
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From page 123... ...
Table 7.3 is a worksheet that shows the ACS data used in the Broward County ID calculations involving the comparison of non-Hispanic whites (Groups a and A) and non-Hispanic blacks (groups b and B)
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From page 124... ...
The actual reported ACS estimates would include lower and upper bounds such as the representative figures shown in the columns on the left of Tables 7.4 and 7.5. The 90 percent confidence level margin of error of the estimates can be calculated by finding the differences between these estimates and the lower and upper bounds.
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From page 125... ...
Table 7.6 shows the results of performing these steps and calculating the corresponding standard errors.
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From page 126... ...
⎡⎣ ⎤⎦ + ( ) ⎡⎣ ⎤⎦2 2 126 A Guidebook for Using American Community Survey Data for Transportation Planning PUMA a/A SE(a/A)
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From page 127... ...
The ID calculations using ACS estimates can be performed in the same way as for the census data by treating the estimates as point estimates, but the analyses can be improved by accounting for the statistical uncertainty of the ACS estimates due to sampling. By keeping track of the standard errors of estimates as they are calculated in the analysis process, data users are able to obtain an estimate of the margin of error of the results.
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From page 128... ...
• An Atlanta benefits and burdens study examined journey-to-work travel patterns (mode, travel time, origin/destination) by race/ethnicity and income, by matching characteristics of workers at residence locations with characteristics of workers at work locations; the study also examined vehicle availability by race/ethnicity, income, and geography.85 • Chicago Transit Agency has used decennial census data on minority status and income as a primary source of quantitative analyses to ensure that transit service is fairly distributed, and any cuts in service (due to budget constraints)
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From page 129... ...
;91 • A study of the differences in origin-destination patterns between drive-alone automobile and streetcar modes in an effort to improve feeder services at major stations by Baltimore transit planners; • Commuter rail feasibility studies (Central Transportation Planning Staff) , and other work by the Delaware Valley Regional Planning Commission, where route planning was supplemented Transportation Market Analyses Using ACS Data 129 87 Cambridge Systematics, Inc., "Technical Methods to Support Analysis of Environmental Justice Issues," prepared for NCHRP Project 8-36 (11)
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From page 130... ...
Use was made of a special tabulation of the Census Bureau's journey-to-work data. 130 A Guidebook for Using American Community Survey Data for Transportation Planning 92 M
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