It's no secret that maps lie to us. In the case of subway and rail maps, those lies are designed to simplify the system just enough to make them intelligible. However, as transit systems become increasingly multi-modal, the need for simple maps that convey the interactions across several modes has grown in importance. In her 2013 thesis, Innovations in Multi-Modal, Schematic, Transit Mapping: An Exploratory Survey, Margaret Finch Carragher (MCRP/ MS-CE '13) examined the effects that multi-modal transit maps could have on transit ridership and overall transit system understanding.

Using the Metropolitan Atlanta Rapid Transit Authority (MARTA) as a case study, Carragher conducted surveys of transit riders and non-riders in order to test visually which network features best integrate multiple modes on paper-based maps. On-board surveys gauged the reaction of train riders to maps displaying bus routes branching off a park and ride lot, bus routes to and from popular destinations, and bus routes with at least 20-minute headways. A second mail-home survey targeted non-riders and bus-only riders in an effort to broaden the study to both customers that need MARTA for basic mobility and customers that can choose to use MARTA. 

Findings from the surveys showed multi-modal maps to be effective tools for improving the legibility of transit systems when compared to current MARTA maps. In addition, 43 percent of survey participants indicated that they would ride the bus more often if they had access to the new maps. However, only 9 percent of non-bus riders reached through the mail-home surveys stated a preference to utilize MARTA bus in the future given access to multi-modal maps. While the potential ridership increases appear modest, Carragher concludes that multi-modal maps that focus on specific network features, such as bus frequencies or landmarks, instead of overwhelming users with all the possible route choices could make MARTA's complex system a little easier to digest. 

Margaret Finch Carragher is a 2013 graduate of Georgia Tech's School of City and Regional Planning and School of Civil Engineering. Advising for her thesis was conducted by Professor Catherine Ross, Assistant Professor Kari Watkins, and Professor Randall Guensler.