When the option « --roadcast-start-date » is used it simply truncate the roadcast to start at the given time, without actually changing how the roadcast is performed. This addition simply remove the first roadcast values before the dedicated time.
If the argument is set before the first roadcast date, it adds values before the first roadcast.
When the argument of --roadcast-start-date has a value preceding the last observation, the observations later than the argument value should be removed. Thus the first roadcast would be at the requested time. I am open to suggestions regarding the expected behaviour of this argument (update the documentation accordingly).
metro --roadcast-start-date 2018-03-27T15:00Z --input-observation observations.xml --input-forecast forecast.xml --input-station station.xml --output-roadcast roadcast3.xml --silent --verbose-level 3 --log-file metro.log