In addition, ODOT recommends southbound traffic that is originating from outside the greater Portland metro area to avoid I-5 South and use I-205 South instead. How does one communicate this in the data? I’m aware that I could tag the closed ramps and section as under construction, but what should I do about the rest of it?
Generally roads should only be changed to ‘under construction’ if they’re going to be closed for more than 3-6 months. The linked article states the closure is planned for 5 weeks so it’s not really long enough to warrant any changes in OSM. As people’s maps may only be updated once a month or only a couple times per year, we don’t want to make any temporary changes which may stick around in people’s maps much longer after we change them back again. However, you could add a tag such as access:conditional=no @ (2018 May 22-2018 Oct 07) which will only restrict access between the stated dates, and won’t cause any problems if it isn’t removed for 2 years. Of course, you’d need to know an approximate end date to make it useful.
Short-term construction should not be mapped, this includes lane narrowing and other temporary changes. As outlined above, many users wouldn’t receive the update in time anyway and might even get it after construction has finished. Apart from the fact that someone would have to reinstate the previous tags.
Things of this nature get close to live traffic data. In some sense, it should be treated as such meaning that it’s better to build such a service on top of OSM, where OSM provides the long-term static data and the particular app provides short-term/live changes to that data.
