Roads may have various kinds of obstructions that makes you drive slower. Tagging them lets software route around them. Consider two otherwise equal routes through a residential area - we prefer the one with no bumps. Just as we prefer the way with no traffic lights.
obstruction=speedbump
Artifical bump that authorites put on otherwise good roads to prevent speeding. Usually a residential road. Going over them at the speed limit is usually so uncomfortable that people slows down, navigation software can consider this. Those few who have a citroën with hydraulic suspension does not need to worry. . .
obstruction=narrowbump
A narrow speedbump that fits between the wheels of a bus. It doesn’t bother buses or trucks, and bikers can easily go around them. Only car drivers need to worry about these. Navigation software may have bus/truck/bike/car/cylce/foot modes already to cope with access restrictions. With this tag, it may also route differently over such bumps.
obstruction=chokepoint
A unusually narrow point of the road, so narrow that you have to pay attention and lower the speed if you meet someone. Could be a cheap bridge, or deliberate in order to prevent speeding.
The proposals seem to be pretty much the same, its just word play that splits them, and that doesn’t matter really. I’ve just updated the bottom one though as it was over a year old, and rather pointless since bridge=yes now exists. Obstruction or obstacles are 2 other words that could have been used, but apart from the intuitiveness of the tag, it doesn’t really have any advantage/disadvantage.
My proposal really covered 3 points (which I have now elaborated on), and barrier= sorts out one of them, which is good, so since its just different wording, that doesn’t matter.
The 2 points that I have elaborated on, that boundary doesn’t cover are:
specific sorts of bridges, so that a wooden plank isn’t muddled up with a large suspension bridge
when obstructions such as a gate are 2 one side of the way, or fall along a way, such a a gate in a hedge, or a gate to one side of the road.
(edit: after editing the page it doesn’t show up in the previous link any more.)
edit2: The barrier proposal seems to include hedge. Key problem there. If barrier is used for linear, and gate= is tagged on the node along the hedge, it will appear adjacent to the hedge, rather than parallel. In my proposal I specifically left out such things, as border= (seperate proposal) could cover them. This would mean if a gate is on a hedge it can be set along, while if its on a highway it can be set adjacent. The is assuming that all gates fall adjacent to what ever passes through them, which frequently not so. People have suggested stating the angle, but realistically this is not plausible. I think if a node has a way attached tagged also as the gate then it should take that angle, otherwise, use the present angles based on the way it lies on. I’m not sure how posible that is, but it would stop the limitations on mapping set by rendering. Discuss…