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Atlanta Regional On-Board Transit Survey Overview of Survey Procedures and Data Processing

Atlanta Regional On-Board Transit Survey Overview of Survey Procedures and Data Processing. Model Users Meeting August 27, 2010. Atlanta Regional On-Board Transit Survey Conducted by . In Association with. & DW & ASSOCIATES. Purpose/Goal. Purpose :

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Atlanta Regional On-Board Transit Survey Overview of Survey Procedures and Data Processing

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  1. Atlanta Regional On-Board Transit SurveyOverview of Survey Procedures and Data Processing Model Users Meeting August 27, 2010

  2. Atlanta Regional On-Board Transit Survey Conducted by In Association with & DW & ASSOCIATES

  3. Purpose/Goal • Purpose: • Collect data from a statistically valid sample of transit riders in the 20-county metropolitan Atlanta area • Identify transit markets and patterns • The results will be used to update the region’s travel demand model • Goal: • Obtain completed surveys from 10% of the transit boardings

  4. Transit Systems Included in the Survey • MARTA • CCT • GRTA • GCT • CAT • HAT • CTran • Emory • Note: Emory routes were not officially part of the survey, but data from Emory routes that was collected by MARTA was included in the final database)

  5. Useable Surveys (use code of 1 or 2)Obtained by System

  6. Key Components • Survey was conducted as a collaborative effort between ARC, MARTA, GRTA and GDOT • Conducted face to face interviews • Used tablet PCs to record interviews • On-going coordination with FTA • Sampling methodology • Data expansion

  7. Sampling Methodology Bus • Collected daily ridership by stop • Stops along each route organized into segments • Goal: Obtain complete surveys with 10% of riders in each segment • Prevented high volume stops from being underrepresented Rail / Bus • Stations and bus stops with >100 daily riders not grouped

  8. Bus Survey Procedures • One bus per route was staffed with 2-3 people between 6:30am-6:30pm • Responsibilities • 1 Person completed Boarding/Alighting Counts • 1-2 people administered surveys • Bus Routes: Participant randomly selected by computer generated number between 1-4 based on the number of people who boarded at each location • High Volume Stop Locations: Every 3rd person who arrived at the stop

  9. Rail Survey Procedures • 8-12 staff assigned to each train station between 6:30am – 6:30pm • Staff assigned to work different areas of the platform and to cover different cars • Every 3rd person who approached a specific point was asked to participate in the survey

  10. Survey Procedures • Interviewers did not have to decide who to interview. The procedures determined who would be interviewed • Mail-back surveys distributed to riders who did not have time to complete the survey • Surveys were precoded so the surveys could be linked to the time and exact location where the survey was given to a rider

  11. Overview of QA/QC Process Performed at each step

  12. QA/QC: Data Collection Controls • High quality interviewers were used • Extensive training was conducted • More than 100 checks were included on the tablet PCs to ensure data collection in the field was complete and accurate • Phone follow-ups were completed with more than 18,000 participants

  13. QA/QC: Pre Processing of Data • All required fields were filled with valid data • Origin address and type of place • Transfers to get to the current route from origin • Mode of access to the transit system • Boarding address • Alighting address • Transfers to get to/from current route to destination • Mode of egress from the transit system • Destination address and type of place • Home address • Number of autos available in household • Household size • Number of adults in household • Number of workers in household • Respondent’s employment status • Respondent’s student status • Driver’s License status • Age of respondent • Annual Household Income

  14. QA/QC: Pre Processing of Data • Performed a series of logic checks • Number of household occupants >= number of employed members of the household and the number of adults • Number of household occupants >= adults in the household • Number of workers >= than the household size • Number of household vehicles was consistent with the household income and number of workers • Place names and street addresses properly and consistently spelled • Reviewed distribution of the results by individual interviewers to identify any of their potential biases

  15. QA/QC: Review of Survey Data • Compared Trip Patterns to Transit Networks • Two Step Process • Used Database and GIS Mapping Techniques • Profile Reports and Maps • Reviewed Trips in Relation to Transit Route • Trip Origin and Destination • Access and Egress Mode • Trip Leg Detail

  16. QA/QC: Profile Reports • Frequencies • Access type • Walk access distance • Trip purpose • Trip distance (straight-line) • Number of transfers • Household size • Number of workers in the household • Household income and autos available

  17. Sample Profile Report

  18. Identify Logistical Inconsistencies • Computed a Trip Ratio Test • Based on the ratio b/t survey trip’s path distance to the straight-line origin-destination distance • Distance from origin point to boarding location • Distance b/t the boarding and alighting locations • Distance from the alighting point to the destination • A ratio above 2.5 indicated there could be a trip logistic issue

  19. QA/QC: Visual GIS Review • Inspect spatial sensibility and key variables • Trips with short distances (short for local bus and rail was < 1.0 mile; for express bus it was 3.0 to 5.0 miles depending on transit provider) • Walk and Drive access trips with zero transfers • Walk and Drive access trips with three or more transfers • Investigate any other suspicious O-D travel based on trip distance and spatial orientation

  20. QA/QC: Visual GIS Review and Assignment Review • Loaded trips onto transit networks • Converted trips into P & A Format • Review assignment • Market segment • Mode of access • Transfer • Transit mode (local bus versus rail)

  21. QA/QC: Refinement • Tagged all survey trips with a quality designation • ‘1’ complete • ‘2’ inconsistent but easily fixed in our opinion • ‘3’ inconsistent and probably difficult to fix • Tagged all survey trips with ‘2’ or ‘3’ with a diagnostic note • Records were revised and reviewed again using the same process

  22. Overview of the Data Expansion Process Separate Methodology for Bus and Rail Performed by Time of Day Iterative Process Coordinated with FTA

  23. Data Expansion Process (RAIL)For Unlinked Trips • Step 1: Review the actual distribution of completed surveys • Step 2: Review the actual ridership between each rail station by time of day • Step 3: Adjust the distribution of actual ridership upward to account for "unknown" trips that were not clearly coded to both a station of entry and exit by time of day

  24. Data Expansion Process (RAIL)For Unlinked Trips • Step 4: Calculate the actual gap b/t the number of surveys completed and the numerical goal set for each cell in the sampling matrix   • Step 5: Calculate unlinked trip expansion factors (Only 15 cells did not meet the original sampling goals that were set for the project) • Step 6: Dummy records were created to simulate trips that were not captured in the survey involving very small numbers of riders traveling between certain stations

  25. Data Expansion Process (RAIL) for Unlinked Trips - Sample

  26. Data Expansion Process (RAIL) for Unlinked Trips - Sample

  27. Data Expansion Process (RAIL) for Unlinked Trips - Sample

  28. Data Expansion Process (RAIL) for Unlinked Trips - Sample

  29. Data Expansion Process (BUS) for Unlinked Trips • Step 1: Review the actual distribution of completed surveys for various stops/segments along each route by time of day   • Step 2: Review the distribution of completed surveys as a percentage of total boardings for each of the segments/major stops along the route by time of day • Step 3: Review the actual boardings (ONs) and actual alightings (OFFs) for each segment/major stop along the route

  30. Data Expansion Process (BUS) for Unlinked Trips • Step 4: Calculate the actual boardings (ONs) and actual alightings (OFF) by segment/major stop • Steps 5 and 6: Apply an iterative process to estimated number of ONs and OFFs from between major stops/route segment along each route • Step 6: Calculate the weighting factors for unlinked trips

  31. Data Expansion Process for LINKED Trips Basic Formula = 1/(1+number of transfers) We may further refine process over time

  32. Preliminary Composition of the Final Database

  33. Final Steps • Finalize Data Expansion and Database • Finalize Linked Trips • Assign trips to networks and evaluate transit skimming, pathing and assignment procedures

  34. Key Preliminary Findings

  35. Trip Purpose

  36. Number of Vehicles Available

  37. Distribution of Riders by Gender and Income

  38. Destinations by HH Income

  39. Mode of Access to Transit

  40. Questions ??? THANK YOU

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