SFMTA TSP

Motivation

• San Francisco has invested in a Transit Signal Priority (TSP) system, which helps buses get green lights more often.
• After implementing TSP on several lines, the city now has data to be able to answer the key question:
  • Is Transit Signal Priority resulting in improvements to travel time for MUNI bus riders?

Goal

• Build a web tool that allows SFMTA staff (and other interested parties) to:
  • Visualize travel time improvement over time at different levels of data, including:
    • Different stops / intersections
    • Various times of day
    • Different kinds of intersection (near vs. far side stop, types of signals)
  • Visualize “dwelltime,” or how long buses stay at different stops
  • Filter and otherwise explore data on their own

Design Strategy

• Visualization Tool
• Key Interaction: Comparisons of Travel Time
  • Stop Type:
    • Outbound vs. Inbound
    • Near side vs. Far side stops
  • Time:
    • Day of Week
    • Time of Day
  • Individual Condition:
    • Traffic Lights between Stops
• Key Metric:
  • Distributions of Bus Speed Before vs. After TSP

Evaluation Strategy

• Analytic Evaluation by the SFMTA staff:
  • A heuristic evaluation by the SFMTA staff providing a rating on the usability of the visualization in answering the key question, “Is Transit Signal Priority resulting in improvements to travel time for MUNI bus riders?”
  • Cognitive walk-throughs of the prototype for specific tasks using available features of the visualization
    • Will the user use a given feature?
    • If so, is the control for the action visible?
    • Is there a perceptible link between control and action?
    • Is the feedback from the feature appropriate?
• Empirical Evaluation by the project team:
  • A qualitative evaluation of the important features of the visualization by:
    • sending questionnaires/surveys to the users asking them specific to rate features of visualizations
    • conducting interviews with the users-- both individually and as part of focus groups, asking specific questions to prompt user’s judgement of the visualization
    • observing the users while using and interpreting the visualizations with and without any directions given by the project team