Refine WorkerPresenceMethod enumerations

[mark-mockett]

Summary

Consider adding/removing values from the WorkerPresenceMethod enumerated type in future versions of the spec to align better with the SwzDeviceFeed, data producer capabilities, and data consumer needs.

Motivation

Enumerated values for the WorkerPresenceMethod may need to be reviewed/refined in the future as the device feed's options change and as data producers begin implementing the WorkerPresence object.

The WorkerPresence object contains an option to specify by what means the data producer knows workers are in the field. As of v4.0, the WorkerPresenceMethod enumerated type includes the following values:

Value	Description
camera-monitoring	Cameras in the work zone event area show workers are present.
arrow-board-present	A GPS-enabled arrow board is located in the work zone event area and broadcasting its location, implying that workers are present.
cones-present	GPS-enabled cones are located in the road event area, implying that workers are present.
maintenance-vehicle-present	A GPS-enabled maintenance vehicle is located in the road event area, implying that workers are present.
wearables-present	Workers wearing wearable detection equipment are present in the work zone.
mobile-device-present	Workers with GPS-enabled mobile device tracking are present in the work zone.
check-in-app	Workers have checked into the work zone via a mobile app.
check-in-verbal	Workers have checked into the work zone via phone or radio to a remote operations center.
scheduled	Workers are scheduled to be in the road event area, but presence has not been confirmed.

Proposed changes

Several of the "proxy" enumerations - those that end with "implying that workers are present" - could be combined if data consumers don't find the differentiation between different equipment types to be useful.

Additionally, to align with the devices included in the SwzDeviceFeed, consider adding:

Value	Rationale
Hybrid Sign	They could represent a digital speed limit sign which is used as proxy for worker presence in some states
Flashing Beacon	Popular in many state to activate flashing beacon when workers are present
Location Marker	That categories includes many others proxy for worker presence. EX: AFAD, flagger, work zone starts/end.

Worker Presence co-chairs propose revisiting the enumeration in a future version of the specification, not in the next release (v4.1, expected August 2022).