Small Geographic Areas
Transportation Analysis Zones are small areas used in transportation planning to summarize demographic characteristics and travel data. TAZs follow census geography boundaries and are generally one or more block groups. Occasionally, however, TAZs are defined at a sub-block group level, that is, collections of census blocks. TAZs are identified by 1- to 4-digit numbers, ranging from 1 to 1151. See below for maps.
TAZ boundaries are revised periodically. The 2010 TAZ structure is the most current, developed using 2010 census geography.
Regional Planning Districts are a somewhat larger district level of geographic detail used in transportation planning to summarize demographic characteristics and travel data for an identifiable area. RPDs follow census geography boundaries and contain one or more census tracts. TAZs generally nest within RPDs, but there can be exceptions to this rule when TAZ geography is at a sub-block group level. RPDs are identified by 3-digit numbers: numbers beginning with1 are in Baltimore City, with 2 in Anne Arundel County, with 3 in Baltimore County, with 4 in Carroll County, with 5 in Harford County, and with 6 in Howard County. There are 94 RPDs in the region.
RPD boundaries have been kept essentially the same since they were developed in the early 1970's. This allows comparison of data over time for a stable geographic unit.
Documents on Small Geographies
Correlation of RPD, TAD, Census Block, Block Group, and Tracts, sorted by TAZ, using Census 2010 geographies: TAZ, RPD, TAD Correlation Table
Complete Report: 2000 Transportation Analysis Zone Structure
Comparison of 1998 and 2000 Transportation Analysis Zones
List of Census Tracts in each Regional Planning District, sorted by RPD, 2000
List of Census Tracts in each Regional Planning District, sorted by Census Tract, 2000
Below are links to maps showing TAZ, RPD and census tract boundaries for all the jurisdictions in the Baltimore region.
Transportation Analysis Zones
Regional Planning Districts
For more information: