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 MeetingAugust 27, 2010

Atlanta Regional On-Board Transit Survey

Conducted by

In Association with

& DW & ASSOCIATES

Purpose/GoalPurpose:

Collect data from a statistically valid sample of transit riders in the 20-county metropolitan Atlanta area Identify transit markets and patternsThe results will be used to update the region’s travel demand model

Goal: Obtain completed surveys from 10% of the transit boardings

Transit Systems Included in the Survey

MARTACCTGRTAGCTCATHATCTranEmory

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)

Useable Surveys (use code of 1 or 2)

Obtained by System

Key Components Survey was conducted as a collaborative effort between ARC, MARTA, GRTA and GDOTConducted face to face interviewsUsed tablet PCs to record interviewsOn-going coordination with FTA

Sampling methodologyData expansion

Sampling MethodologyCollected daily ridership by stopStops along each route organized into segmentsGoal: Obtain complete surveys with 10% of riders in each segmentPrevented high volume stops from being underrepresented

Bus

Rail / Bus Stations and bus stops with >100 daily riders not grouped

Bus Survey ProceduresOne bus per route was staffed with 2-3 people between 6:30am-6:30pm

Responsibilities1 Person completed Boarding/Alighting Counts1-2 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

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

Rail 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

Survey Procedures

Overview of QA/QC Process

(From riders at 235 bus routes or rail stations lo-cated throughout region)

COLLECT DATA(Build db of transit trip records. Identify those records that comply with completeness and stage-1 logic checks)

PRE-PROCESS DATA(Add travel forecast model variables to survey db. Conduct visual inspection and outliar tests. Tag survey trips that are perplexing in logistical sense)

QA/QC REVIEW

(Fix data that was flagged during QA/QC Review. Update sample counts by stratification parameters)

REFINEMENTS/EXPANSION

Performed at each step

QA/QC: Data Collection Controls

High quality interviewers were usedExtensive training was conductedMore than 100 checks were included on the tablet PCs to ensure data collection in the field was complete and accuratePhone follow-ups were completed with more than 18,000 participants

QA/QC: Pre Processing of DataAll required fields were filled with valid data

Origin address and type of placeTransfers to get to the current route from originMode of access to the transit systemBoarding addressAlighting addressTransfers to get to/from current route to destination Mode of egress from the transit systemDestination address and type of placeHome addressNumber of autos available in householdHousehold sizeNumber of adults in householdNumber of workers in householdRespondent’s employment statusRespondent’s student statusDriver’s License statusAge of respondentAnnual Household Income

QA/QC: Pre Processing of DataPerformed a series of logic checks

Number of household occupants >= number of employed members of the household and the number of adultsNumber of household occupants >= adults in the householdNumber 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 spelledReviewed distribution of the results by individual interviewers to identify any of their potential biases

QA/QC: Review of Survey DataCompared Trip Patterns to Transit NetworksTwo Step Process

Used Database and GIS Mapping Techniques

Profile Reports and MapsReviewed Trips in Relation to Transit Route

Trip Origin and DestinationAccess and Egress ModeTrip Leg Detail

QA/QC: Profile ReportsFrequencies

Access typeWalk access distanceTrip purposeTrip distance (straight-line)Number of transfersHousehold sizeNumber of workers in the householdHousehold income and autos available

Sample Profile Report

Identify Logistical InconsistenciesComputed a Trip Ratio TestBased 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

QA/QC: Visual GIS ReviewInspect 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 transfersWalk and Drive access trips with three or more transfers

Investigate any other suspicious O-D travel based on trip distance and spatial orientation

QA/QC: Visual GIS Review and Assignment ReviewLoaded trips onto transit networks Converted trips into P & A FormatReview assignment

Market segmentMode of accessTransferTransit mode (local bus versus rail)

QA/QC: RefinementTagged 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

Overview of the Data Expansion Process

Separate Methodology for Bus and RailPerformed by Time of DayIterative ProcessCoordinated with FTA

Data Expansion Process (RAIL)For Unlinked Trips

Step 1: Review the actual distribution of completed surveysStep 2: Review the actual ridership between each rail station by time of dayStep 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

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

Data Expansion Process (RAIL) for Unlinked Trips - Sample

Data Expansion Process (RAIL) for Unlinked Trips - Sample

Data Expansion Process (RAIL) for Unlinked Trips - Sample

Data Expansion Process (RAIL) for Unlinked Trips - Sample

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 dayStep 3: Review the actual boardings (ONs) and actual alightings (OFFs) for each segment/major stop along the route

Data Expansion Process (BUS) for Unlinked Trips

Step 4: Calculate the actual boardings (ONs) and actual alightings (OFF) by segment/major stopSteps 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

Data Expansion Process for LINKED Trips

Basic Formula = 1/(1+number of transfers)

We may further refine process over time

Preliminary Composition of the Final Database

Final StepsFinalize Data Expansion and DatabaseFinalize Linked TripsAssign trips to networks and evaluate transit skimming, pathing and assignment procedures

Key Preliminary Findings

Home-Based Work

44.7%

Home-Based Other15.3%

Non-Home Based10.3%

Home-Based

College8.4%

Home-Based School7.7%

Home-Based

Shopping7.1%

Home-Based

Medical4.1%

Home-Based Airport1.4%

Non-Home Based Airport0.9%

Trip Purpose

0 vehicle40.7%

1 vehicle32.0%

2 vehicle19.4%

3 vehicle7.9%

4 or more vehicles

0.0%

Number of Vehicles Available

0.0%2.0%4.0%6.0%8.0%

10.0%12.0%14.0%16.0%18.0%

Male Female

Distribution of Riders by Gender and Income

0.0% 10.0% 20.0% 30.0% 40.0% 50.0%

Place of WorshipMedical

Bank/Other OfficeRecreation

HotelAnother Home

RestaurantStore/Retail

School/DaycareOther

College/UniversityAirport

WorkHome

>$75,000 < $20,000

Destinations by HH Income

Mode of Access to Transit PercentWalked 72.4%Dropped Off 14.0%Drove Alone 10.6%Rode in a vehicle for part of the trip and walked/biked rest of the way 1.8%Carpooled/Vanpooled 0.9%Bicycle 0.3%

Mode of Access to Transit

Questions ???

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