Most people between the ages of 16 and 65 have access to a car and can drive. Adolescents and many of the elderly, however, cannot drive, and therefore often depend on transit to make their way around town. In addition to illustrating the population density of all age groups within each census tract in Los Angeles County, the map allows a user to click anywhere on the map to see an age profile for the tract. The map uses 2010 Census data and shows the proportion of each census tract that is less than 5 years old, 5 to 17, 18 to 21, 22 to 29, 30 to 39, 40 to 49, 50 to 64, and age 65 and up. Those neighborhoods with more youth and more elderly have many residents who cannot drive because of their age, and would thus benefit from better transit access.
Here is an interactive window the the live map and a link to the full map: