Enum Mode

// Log all available data for a public-transit trip.
var directions = Maps.newDirectionFinder()
    .setOrigin('The Cloisters, New York, NY')
    .setDestination('JFK airport, New York, NY')
    .setMode(Maps.DirectionFinder.Mode.TRANSIT)
    .setDepart(new Date())
    .getDirections();
var route = directions.routes[0];
Logger.log(route);