Population and Public Streets in Brooklyn
Brooklyn's reshus harabim question involves more than the resident count inside a proposed route.
More than the residents inside a route
A census count for a proposed eruv area describes the people who live there. It does not include the larger population whose streets, institutions, businesses, and transportation network extend through the same neighborhood.
Commuters, visitors, students, shoppers, transit riders, and people passing between neighborhoods all use Brooklyn's public ways. Which of them enters the halachic count depends on the accepted view of shishim ribo.
Major public routes
Wide avenues and connections to bridges, tunnels, transit centers, and the rest of New York can place a local street inside a much larger system. The route must be followed beyond the drawn neighborhood line.
Road width is only one part of the definition. Openness, alignment, access, public use, and the relationship of the street to the whole city also matter.
Use the right figures for the halachic question
Census data, vehicle counts, pedestrian counts, and transit ridership measure different things. A calculation should identify whether it concerns residents, passages, one road, or the roads serving the city.
Specific figures can clarify the Brooklyn question only when their area, date, unit, and relationship to the psak are made explicit.