Per the Federal Highway Administration Office of Planning, Environment and Realty the Top 30 Counties with Highest Transit Share increases between the Year of 2000 and 2007-2009 (Journey to Work Trips) include 4 Maryland counties and here they are with their ranking:
2 Prince George’s County, Maryland
7 Charles County, Maryland
12 Montgomery County, Maryland
23 Howard County, Maryland
B’ Spokes: And I’ll note that there are similar analyses for biking and walking but no Maryland county made that list (no surprise there)
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Walking: https://www.fhwa.dot.gov/planning/census_issues/ctpp/data_products/2000_2007-2009_2010-2012_commute_shares/walkshare.cfm
Biking: https://www.fhwa.dot.gov/planning/census_issues/ctpp/data_products/2000_2007-2009_2010-2012_commute_shares/bikeshare.cfmoldId.20141116155042546