Enum Mode

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