Add new optional field SeverityLevel to Service Alerts feed

[ibi-group-team]

This is a proposal to add a new field SeverityLevel to the ServiceAlerts feed. The SeverityLevel field would be optional and comprised of enum values:

• UNKNOWN_SEVERITY
• INFO
• WARNING
• SEVERE

See discussion here: #133

Announced on the GTFS-realtime Google Groups here: https://groups.google.com/forum/#!topic/gtfs-realtime/t8bpU5gbjDU

[LeoFrachet]

Looks good!

Two small suggestions:

1. Please add the space missing in the comment, to stay consistent with the rest of the doc: //Severity => // Severity
2. Andrew (@abyrd) and Sean (@barbeau) in the issue Add new field SeverityLevel (enum, optional) to Service Alerts feed #133 suggested INFO instead of INFORMATIONAL. I have no strong opinion. I slightly lean toward INFO but I have no opposition toward INFORMATIONAL.

[barbeau]

I also have a preference for INFO but no strong objection to INFORMATIONAL

[abyrd]

Initially I had a preference for INFO over INFORMATIONAL. But on further reflection I think this is just because the value INFO is often used in logging, which is really a different application. I can see why we'd want to avoid abbreviations in enum values. INFO in this case may stand for INFORMATIONAL, or does it stand for INFORMATION? Either way the grammatical parallelism with the other enum values is questionable.

I think the main argument for INFO is that it is concise and not strictly an adjective or a noun. It seems like more people prefer INFO but I wouldn't actively oppose INFORMATIONAL.

[ibi-group-team]

This pull request has been open for more than one week, so we are calling for a vote.

Voting will be closed on Thursday January 31 at 23:59:59 UTC.

[laurentg]

Just as a side note, in our Urbiplan alerts product we already have this severity level. We use 3 levels: INFO, WARN, CRITICAL. +1
Also we would be ready to output GTFS-RT alert feeds with this severity level field rapidly if this change is accepted.

[abyrd]

+1

[skinkie]

+1

[paulswartz]

+1

[gcamp]

+1

[barbeau]

+1

@ibi-group-team There are a few formatting items I commented on that need to be fixed prior to merge.

Also, as a side note, the conventions proposed here match Google's severity levels (Critical, Warning, Informational) inferred from Alert Effects as listed on https://support.google.com/transitpartners/answer/6374472?hl=en&ref_topic=6159819.

[prhod]

+1

[harringtonp]

+1

[ibi-group-team]

Voting for this proposal is closed and the results are:
Yes: 8
No: 0

So the proposal passes! We'll get this merged.

Thank you all!

[barbeau]

Thanks @ibi-group-team and all!