By Bill Holloway
Transportation agencies traditionally have to chase land use development, spending scarce funds to provide new roadway capacity, when better land-use patterns could have greatly reduced travel demand.
SSTI’s new scenario analysis tool, developed for DelDOT, provides a way for transportation providers to influence land use development for the better.
LUTSAM – the Land Use and Transportation Scenario Analysis and Microsimulation tool – debuted in April at a training session in Baltimore. An SSTI webinar was also held on the topic in February. LUTSAM was developed by Whitman, Requardt, & Associates, with support from SSTI.
The tool integrates GIS, transportation modeling, and microsimulation software to dramatically speed scenario analysis and better demonstrate the benefits of both compact, mixed-use development and of improved bicycle and pedestrian facilities.
Because DelDOT controls the vast majority of the roadway lane-miles in the state, the organization has been concerned with modeling traffic patterns at a level of detail more akin to that used by local governments and MPOs than most other states. Prior to SSTI involvement, DelDOT had beeen using individual tax parcels as smaller traffic analysis zones (TAZs) in order to quantify bicycle and pedestrian mobility. TAZs are geographical areas used in transportation modeling, conventionally several square miles in size. Travel demand models estimate the number of trips that will occur between these zones. However, a travel demand model using these standard sized TAZs is unable to measure walking and biking trips, because most of these trips occur within a single TAZ.
Beyond the move toward smaller TAZs, DelDOT had also been working to quantify the impact of sidewalks on travel behavior and better demonstrate to the public how much a specific section of sidewalk might reduce vehicular travel. While planners and smart growth advocates have know for a long time that building pedestrian infrastructure lowers auto traffic, the impact of a specific section of sidewalk has been difficult to determine.
DelDOT was also concerned that large-lot, single-use development was generating high traffic volumes. To land use authorities, spreading out land uses might seem desirable, as it spreads out traffic generators. But the greater number and length of car trips that result have negative consequences – both to the community and the transportation agency’s budget. Demonstrating these outcomes has been a challenge.
While DelDOT had been able to model transportation demand for new developments in various ways – with good or poor connectivity, compact or sprawling layout – doing so manually was time consuming, limiting the number of scenarios the department could produce.
LUTSAM allows users to design new residential and commercial developments using standard GIS software and connect the development to the existing road network to assess its impact on travel patterns. By streamlining the process of constructing these developments and linking them to the road network, planners can evaluate more development scenarios to present to their communities. In addition, LUTSAM allows these scenarios to be depicted using 3-D microsimulation software, showing congestion, queuing, turning movements, and other traffic patterns.
Along with DelDOT staff, representatives from the Maryland and North Carolina DOTs attended the Baltimore training session to explore how LUTSAM could be used in their states. The February webinar is available for viewing. If you would like additional information, or would like to talk to someone at SSTI about using LUTSAM at your organization, contact Bill Holloway or Eric Sundquist.
Bill Holloway is a Transportation Policy Analyst at SSTI. He can be reached at holloway@ssti.us.