America's cities are growing faster than every before. As of 2016 the Census Bureau estimates that over 80% of all Americans live in an urban area. Increasing urbanization presents numerous problems, however. Chief among these problems is access to transportation as transit networks are being strained under this increased demand. Inevitably some areas of cities are not being adequately served by current transit networks. Transit dependent populations (those who do not or cannot drive) are particularly vulnerable to being under-served by transportation networks. A "transit desert", a term coined by Dr. Jiao, describes an area of a city where transit demand, measured as the transit dependent population, outstrips transit supply. This research aims to identify these transit deserts in 50 major US cities by using GIS based analysis methods, developed in the Urban Information Lab led by Dr. Junfeng Jiao, that are quick to implement and flexible. Moreover, by focusing on transit dependent populations we can identify areas of cities, in need of more transportation, that traditional transit planning methods may miss. For each city the the unit of analysis is the Census Block Group, essentially equivalent to a couple city blocks.
The supply metrics vary by city as the transit supply is different for each city. However, in general, the metrics include street length, sidewalk length, public transit network(s) route length, bike lane route length, number of public transit stops, number of street intersections and the average number of public transit trips per hour and number of trips per day. The demand (transit dependent population) for each block group is again calculated using processing models in ArcMap using data from the American Community Survey 2011-2015. A negative gap between demand and supply is considered a transit deserts.
Through this analysis, we have found that the central business district is almost always well served by transit. Outer lying areas in which people generally own vehicles are also well-served, but this is not always the case. High-density, residential, urban areas are generally the least well served areas of any given city because people are less likely to own cars in these areas and thus demand is high. This research highlights some of the shortcomings in traditional transit planning approaches because such methods almost always focus on easing daily commute times instead of taking a more holistic look at cities. Possible solutions to transit desert problems, include but are not limited to shared biking systems, Transit Network Companies i.e. Uber, informal transit systems (van-pool), or customized transit systems.
Junfeng Jiao
