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Updates are released annually. Each update requires an actual visit to each exit. Zenrin's annual updates begin in February, and new datasets are released every year in mid November.
Each year, we begin our first round of data validation via telephone calls. All businesses are called and asked for specific information to determine if anything has been added or changed since the previous year. Phone numbers that are out of service are flagged and verified by the field research team.
After all phone validation is completed and confirmed, field sheets are printed and sent to the field researchers. Once an interstate within a state is verified and updated, it is then sent back to Zenrin where it is double entered into the database by our data entry team. Random quality checks are performed constantly to ensure an accurate data set.
Currently the Interstate Exit Database covers over 500 freeways, and consists of information recorded for over 36,000 exits and more than 120,000 businesses and services.
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