MARTA TypeScript client

A Node.js client for MARTA bus GTFS Realtime feeds and rail arrivals. Independent community project; not an official MARTA SDK.

Requires Node.js 24+. Ships ESM JavaScript and TypeScript declarations.

Install

npm install marta

Usage

import { Marta } from 'marta';

const marta = new Marta();

// Bus feeds do not require an API key.
const positions = await marta.buses.getBusVehiclePositions();
for (const entity of positions.entity) {
    if (!entity.vehicle) continue;
    console.log(entity.vehicle.trip?.routeId, entity.vehicle.position);
}

const trips = await marta.buses.getBusTrips();
for (const entity of trips.entity) {
    if (!entity.tripUpdate) continue;
    console.log(entity.tripUpdate.trip.tripId, entity.tripUpdate.stopTimeUpdate);
}

// Rail queries require a key; this can also come from MARTA_API_KEY.
const authenticated = new Marta({ apiKey: process.env.MARTA_API_KEY });
const trains = await authenticated.trains.get();
for (const train of trains) {
    console.log(train.STATION, train.DESTINATION, train.WAITING_SECONDS);
}

Importing the library and constructing clients perform no requests. The library reads MARTA_API_KEY at construction but does not load .env files. Applications can use Node's --env-file=.env option themselves.

Get a rail key through MARTA's developer resources. Rail requests use the documented apiKey query parameter. Bus requests send no key.

API

Method	Return	Timeout
marta.buses.getBusVehiclePositions()	Promise<BusFeed>	20 seconds
marta.buses.getBusTrips()	Promise<BusFeed>	20 seconds
marta.trains.getTrainArrivals()	Promise<TrainArrival[]>	5 seconds

BusFeed is the decoded FeedMessage from gtfs-realtime-bindings. The full snapshot is retained, including its header, trip relationships, and stop updates. No cancellations are filtered out. Protobuf 64-bit timestamps may be Long objects; use Number(value) when converting supported timestamps to Unix seconds. Optional protobuf fields can have inherited defaults; check field presence before interpreting a missing field as zero or an empty string.

TrainArrival preserves MARTA's original uppercase field names and string values: DESTINATION, DIRECTION, EVENT_TIME, LINE, NEXT_ARR, STATION, TRAIN_ID, WAITING_SECONDS, and WAITING_TIME. Optional IS_REALTIME, DELAY, LATITUDE, and LONGITUDE fields are typed as strings when supplied. Additional fields are preserved as unknown. Empty arrays are valid. Invalid response shapes reject.

Services and types are exported from the package root:

import { BusService, TrainService } from 'marta';
import type { BusFeed, TrainArrival, MartaOptions } from 'marta';

const buses = new BusService();
const trains = new TrainService({ apiKey: process.env.MARTA_API_KEY });

const busStops = await buses.getTrips()
const busPostions = await buses.getPositions()
const trainArrivals = await trains.getArrivals();

Every call gets a fresh timeout. Non-2xx HTTP responses, malformed responses, network failures, and timeouts reject the promise. Missing rail credentials reject before a request is made. There are no automatic retries or caches.

Release scope

Version 1.0.0 provides current feed snapshots. It does not provide historical data, static schedules, stop-time windows, route-name lookups, or normalized bus arrivals and departures. Filter feed entities in your application. Browser use and CommonJS are not supported by this release.

Development

npm ci
npm run check

check runs type validation, mocked transport tests, and the production build. Tests require no network or API key. Build output goes to dist/.

After building, run node examples/basic.mjs for live bus checks, or node --env-file=.env examples/basic.mjs to include rail arrivals.

Publishing

Release preparation: the current name marta is already registered to another maintainer. Set a package name you own (and update these examples and the lockfile) before publishing. Then:

npm run check
npm run test:package
npm pack --dry-run
npm pack
# Install the tarball in a separate project and check its imports before publishing.
npm publish --access public

prepack builds the package; prepublishOnly runs the complete check. Only build output, this README, and the ISC license are distributed. The package contains no example execution, credentials, tests, or prototype source files.

License

ISC. See LICENSE.