I have noticed that almost no one puts tag
highway=stop
on the crossroads where every road has a stop sign.
(Such crossroads are very common in the USA.)
However, in the default version of mapnik my stop signs are not rendered.
In order to render them I had to make a few changes to the file
inc/layer-amenity-points.xml.inc
(Those who are interested -- please ask me, I'll explain the changes.)
The fact that the "all-way" stop signs are not rendered prevents many people from including them. (Analogously, I am unhappy that the car-washer which I have put on the map is not rendered too.)
As a result, it is not easy to estimate traveling time using openstreet map, and this is sad. I propose to render stop signs on the map by default.