Real-Time Data in GTFS-realtime Format

GTFS-realtime is a new standard developed by Google for delivering real-time data. It is in Protocol Buffer format and needs to be combined with General Transit Feed Specification (GTFS) schedule data to be meaningful. The result is a highly efficient way to deliver data about many routes and vehicles at once using a minimum of bits and with total GTFS compatibility.

As of August 22, 2011, the MBTA is making real-time data on all of its bus routes available in GTFS-realtime format. There are two files, one containing trip progress and predictions, and one containing vehicle locations. This is not intended as a replacement to the existing feed described on the Real-Time Bus Data page. The two feeds have different strengths: the Bus Data feed is easier to use on its own for queries of just one stop or one route, and provides predictions calculated by NextBus Inc’s specialized algorithm; the GTFS-realtime feed lets you get information on all buses at once when combined with GTFS and provides predictions from a comparatively simple algorithm.

Use of the Feed

Access to the MBTA GTFS-realtime Feed is governed by the language in the MassDOT Developers License Agreement in addition to the following conditions:

• The MBTA reserves the right to suspend the data feed, modify the feed, or modify elements of the feed at any time in the MBTA's sole and absolute discretion.

• The MBTA will not guarantee any technical support of any kind to users.

• No user may execute polling commands more often than every 10 seconds.  A user that polls more often than that or otherwise overtaxes the MBTA's system may be suspended or terminated from the data feed.

More about GTFS-realtime

Google has published documentation on the GTFS-realtime format, including the .proto file which is necessary to interpret it.

More about Protocol Buffers

Google has published documentation on the Protocol Buffer fomat.

Accessing the Data

We currently publish two .pb files:

• Trip updates
• Vehicle positions