BROOKLYN - Some of the city's most dangerous intersections for pedestrians and bicyclists are right here in Brooklyn, according to a new study by an advocacy group.The study by Transportation Alternatives found that the areas with the most crashes involving pedestrians are Flatbush, Ditmas Park and Midwood. The study was based on data from 1995-2009, when nearly 4,000 crashes occurred in Community District 14.The safest neighborhoods for pedestrians are Brighton Beach, Coney Island and Gravesend, the group says. Less than 1,700 crashes occurred in those areas over the same 14-year period, according to the data.