Glossary
Transit
- Headway
- Time between consecutive vehicles at a stop.
- Dwell
- How long a vehicle sits at a stop.
- Travel time
- Time to get from one stop to another.
- Slow zone
- A stretch of track where trains are consistently slower than normal. We detect these from travel times.
- Speed restriction
- An official MBTA order to run slower on a stretch of track. Often the cause of a slow zone.
- Delivered trips / service
- How many trips actually ran, compared with how many were scheduled.
- CR
- Commuter Rail.
- The RIDE
- The MBTA's paratransit service.
Data
- GTFS
- General Transit Feed Specification: the standard format for schedules, stops and routes. See Data sources.
- GTFS-RT
- GTFS-Realtime: live vehicle positions and predictions.
- V3 API
- The MBTA's main developer API.
- LAMP
- The MBTA's published performance data: every arrival and departure.
- Events
- Our name for arrival/departure records, stored as CSVs in S3.
- Blue Book
- MassDOT's open data portal.
Infrastructure
- Chalice
- An AWS framework for writing Python Lambda apps that look like Flask.
- Lambda
- AWS's "run this function on demand" service. We pay only when it runs.
- S3
- AWS file storage.
- DynamoDB
- AWS's NoSQL database. We use it for pre-aggregated time series.
- CloudFront
- AWS's CDN. It sits in front of our S3-hosted sites.
- CloudFormation
- AWS infrastructure-as-code. Each app's
deploy.sh updates its stack.
- Beta
- A copy of an app at
*-beta.labs.transitmatters.org, for testing before production.