Impacts of Network Connectivity on Multimodal Travel Metrics

In recent years, the transportation planning sector has witnessed a steady growth in the design and implementation of policies and projects aimed at providing infrastructure not only for automobiles, but also for pedestrians and bicyclists. In the United States, multiple cities have implemented policies and design frameworks to encourage more pedestrian and bicyclist activity. Providing increased connectivity is commonly held to facilitate these modes of travel, but connectivity has a complex relationship with drivers' route choices. Because interactions with motor vehicles are a major factor in pedestrian or bicycle comfort levels, connectivity has a complex interaction with nonmotorized modes as well. This paper presents a methodology for quantifying these interactions, paying particular attention to impacts on the bicycle and pedestrian modes in addition to vehicular modes. The use of active transportation indices (ATIs) play a central role in this analysis, linking shifts in vehicular volume to suitability for nonmotorized travel. This methodology is tested on networks representing the southern part of the Austin, Texas metropolitan area, but the formulation is generic and readily transferable to other regions. Results of this application indicate that average path travel times between origins and destinations within the network and the link-congestion attributes like the volume-to-capacity ratio rise with reductions in connectivity and network-accessibility at both the South Austin regional (full-network) level and also at the local (intersection) levels where ATI indices are affected in addition to them. Additionally, improved vehicular networks have favorable effects on pedestrian and bicyclist activity, also shown in this study through the isolated attribute of traffic volumes.