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University of Washington
Handling Bias in Large Urban DatasetsUsing Smart Fare Card Data for Transit Planning
Mark Hallenbeck, Mayuree Binjolkar, Daniel Dylewsky , Andrew Ju, Wenonah Zhang, Michael Wolf
STATISTICAL BIAS ANALYSIS
Sponsoring Agencies
Origin-Destination Data from Orca is Biased Against Short Duration Trips
Chose Semi- Supervised Based Machine Learning Approach for Classification of
Types of Transfers
RealTransferFinancialTransfer
Transfer Classification Results by Stop
MarkerSize=TransferCount
• Not all transit users are ORCA users• Need to account for cash-paying
customers for business planning • Compare limited passenger count data
to ORCA data
ORCA can combine Two Trips into oneTrip A + Trip B = long trip with transfer
Research Task:•To determine if a transfer was real or financial•If transfer is financial then create new origin –destination pairs
MOREFALSETRANSFERS
MOREREALTRANSFERS
ORCAUnderestimatesTotal
ORCA=Total
ORCAOverestimatesTotal
Outcome of Transfer Classification
Number and Type of Transfer Activity
Example of ORCA Financial Transfers
APC (Automatic Passenger Count) and ORCA Factors by Traffic Analysis Zones
Future Work• Rebuilding origin-destination data files
using transfer analysis results• Deploy Hidden Markov Models for
statistical bias analysis