Access to Opportunity Updates

ATO Calculation Updates

In previous model versions, access to opportunity (ATO) was calculated using a decay curve. The same decay factor was used for both auto trips and transit trips (walk-to-transit only). In version 9.1.1, the ATO factor curve was updated and expanded. A distance-based factoring methodology is now applied to an expanded mode set including auto, walk-to-transit, drive-to-transit, bike, and walk. See Figure 1 to view a comparison of the new ATO factor curves and the previous decay curve. Note that each mode has a different factor curve based on perceived behavior and benefit. Also note that all trips within 10 minutes count in full regardless of mode.

Figure 1: ATO Factor Comparison

The changes to the ATO calculation were made for a variety of reasons, some of which are listed below:

  • a calculation rooted in visioning
  • a methodology consistent over time
  • a metric that is easy to communicate
  • a methodology that can be applied uniformly across Unified Planning processes
  • the inclusion of other travel choices (bike, walk, drive-to-transit)

Overall, the new ATO methodology is more robust and better represents a planner’s perspective on travel behavior.

Model Updates

The specific updates made to the ATO calculation were implemented in the 2_ModelScripts/5_AssignHwy/08_Access_to_Opportunity.s script. A folder with ATO weights and presentation materials presenting the new methodology has been added in the 0_GlobalData\7_ATO folder.

In addition to adjusting the decay curve to match the factors in Figure 1, new comparison fields were added. These comparisons include:

  • ATO (Job & Household) Loss due to Congestion shows the loss in auto access due to congestion as compared to free flow access.
  • ATO (Job & Household) Loss due to Network Inefficiencies shows the loss in auto access due to free-flow network connectivity as compared to a free-flow straight-line access.
  • ATO (Job & Household) Total Loss is the total of both Congestion and Network Inefficiencies.
  • ATO (Job & Household) compared to Geographic ATO Averages is the ratio of average number of jobs or households that are reachable within a typical commute to the average for a given geography.

The ATO compared to the geographic averages was calculated in a new python script as_AccessToOpportunity.py. This script runs as an intermediate step between the TDM voyager script for ATO output and the vizTool scripts.

The vizTool was adjusted accordingly to visualize the new attributes. For specific updates to the vizTool, please refer to the vizTool source code GitHub repository.