Yes, exactly. As funding gets pulled from public transit budgets, routes run less and less frequently.
In Florida (where I lived before Baltimore) it can take two and a half hours by bus to travel what takes around 20 minutes by car, but there the grocery stores are plentiful because of the immense urban sprawl.
In Baltimore and DC, there are literally almost no grocery stores in large swaths of the city, and not a lot of bus lines, because why would buses run often to places with no commerce? Some heavily traveled lines are between a half hour and an hour late, regularly.
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This[1] is a map of food deserts in DC, which doesn't include Prince George's County (where most of the gentrification is pushing lower-to-middle-class [almost entirely black] families that can't afford living in DC anymore). Note that children are highly affected. There have been studies showing the lack of nutrition for children severely affects their development.
This[2] page from Baltimore City Planning lays out the numbers, in which 1/3 of Baltimore neighborhoods lie in a food desert (we're not as well off as DC's metro-accessible gentrified and developed areas; our metro is a joke). It's much easier to find Ramen noodles than it is a piece of fruit, or non-fried foods.
Walmart has been trying to break into DC and Baltimore for years, and is coming very close, partly on the argument that it would lessen food deserts. But the reality shows that they are pushing hard for long, large flat parking lots and super-centers, which 1. increases car traffic to an already congested urban neighborhoods, 2. removes store space and convenience for small businesses, which in turn 3. reduces the number of small businesses available to sell healthy food to locals, because they can just get everything at Walmart.
This results in no additional relief for the majority of residents in food deserts, while reducing the number of small businesses that could have provided better food service, and making traffic worse for public transit (which is already stressed).
The USDA had a map of food deserts from 2010 but it's not working for me. Maybe someone can download the data from here[3] and plot it in some JavaScript library?
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[1] http://dcentric.wamu.org/2011/05/mapping-d-c-s-food-deserts/...
[2] http://www.baltimorecity.gov/Government/AgenciesDepartments/...
[3] http://www.ers.usda.gov/data-products/food-access-research-a...