Ambiguous value of total_num_lanes #140

Background

Lane numbering, whether something like a shoulder counts as a lane, and related topics have been a subject of much discussion throughout the WZDx spec development. The v3.0 release added the order property to the Lane object to identify a lane's position on the roadway rather than using lane_number for this as agencies were using lane_number differently. Most importantly, they are using the lane number when speaking about lanes (e.g. "lane one is closed"), in the typical case, a shoulder or bike lane (which are "lanes" in WZDx terms) would not be given a lane number and would not be counted in total_num_lanes on the RoadEvent.

Problem

It is not clear whether total_num_lanes should be the number of standard general travel lanes (traditionally numbered lanes) or all WZDx lanes.

Practically, that means total_num_lanes could differ from the length of the lanes array on a RoadEvent.

Note if lanes are provided, regardless of how total_num_lanes is being used, it does not provide any additional information as it can be gathered from the lanes array.

Next steps

It needs to be clarified what the value of total_num_lanes should reflect.