GIS can be effectively used to help in transportation planning and in predicting public transit ridership. This product helps to determine current transit ridership and uses spatial analysis to find ways to increase the transit mode share for transit corridors through targeted investment. It can also help determine the effects of corridor improvement on existing land use and ridership patterns.

This product can be used to model transit ridership based on factors like proximity (distance to stations); frequency (headways at serving stations); and accessibility (regional connectivity of serving stations) on transit ridership. In short, we attempted to quantify the effects of these variables on transit ridership in our analysis by regressing on selected household characteristics and these three transit quality measures.

GIS can effectively be used to predict the best places for transit stop placement along the corridor. Our model can help predict ridership potentials and determine the optimal placement of stops based on these ridership potentials. Additionally, questions can also be answered about potential riders, such as: Where are the greatest concentration of potential rider groups that have, as of yet, been untapped by current transit service? These groups could include students, the disabled, etc. How can the system be improved to attract these riders?

Transit GIS analysis can also be used to answer to following questions:

• Accidents: Where do accidents occur within the corridor? What modes are involved? Based on this information, where are the hot spots for accidents with potential modes and how should these areas be bypassed or made safer for any major investment?
• Crime: Safety is one of the greatest concerns of transit riders. Where are crimes occurring in the corridor? Are they near transit stops? How should stop placement of any new investment be changed to mitigate effects of crime in the corridor on transit ridership?
• Design: How are pedestrians influenced by environmental factors? How does land use play a role in determining both ridership and appropriate spaces for investment?

This process is based on a project carried out by SIG principals for Cambridge Systematics and AC Transit, while they were PhD students at UC Berkeley.