Regarding your question in a parallel thread:
To be clear, I think routers should penalize roads that aren’t wide enough to allow passing. This is one reason why routers already penalize service=alley so heavily by default. But here we have an example of a region in which residential roads are indistinguishable from alleys in general.
oneway=alternating would indicate that the driver has to wait until opposing traffic has cleared the roadway. In the U.S., we use this tag often on one-lane bridges, but I suspect most mappers consider it to be implied by service=alley. OSRM penalizes oneway=alternating by a guesstimated delay of 40%. Some renderers might also draw two-way arrows based on this tag.