[Talk-us] Possible roundabouts?

[Minh Nguyen]

On 2018-09-06 23:27, Marian Poara wrote:
> 40.5234202, -111.8762446

Despite its size, the standard roundabout rules normally apply on these 
decorative or traffic calming circles -- there simply isn't enough room 
for a driver inside the circle to yield to a driver entering the circle. 
So junction=roundabout is still justified.

This roundabout is small enough that OSRM classifies it as a "roundabout 
turn", but only if the circular way is tagged junction=roundabout. 
Otherwise, you'd get confusing guidance like "Turn right, then turn right".

> 35.8497728, -86.4547473

This is definitely a roundabout, to be tagged junction=roundabout. Bing 
imagery shows a yield sign at each of the four approaches. Even without 
street-level imagery, you can see pedestrian islands in the middle of 
all four approaches, a hallmark of modern roundabouts in the U.S.

> 42.6811136, -73.6987507

This could either be considered a roundabout (junction=roundabout) or a 
turning loop that happens to have two driveways sprouting out from it. 
Either way, given the width of the loop, the loop is one-way.

Incidentally, it's kind of awful that a four-lane road would abruptly 
end in a one-lane turning circle without any signage at all.

> 40.22109, -76.874981

This is ambiguous. Based on the road width alone, you wouldn't be able 
to tell that the circular road is even one-way. But in Mapbox imagery, 
you can clearly see from the wear on the pavement that drivers are 
treating it like a one-way road, only turning right onto it from each of 
the three approaches. As long as it's a one-way road, it would most 
likely be a junction=roundabout as well.

> And if we have OSC or Mapillary street level 
> images and it is confirmed that they don’t have any roundabout sign? In 
> many residential areas (but not only), there isn’t any one way sign 
> inside the small “roundabouts” and it seems that both directions are used.

In residential areas, you'll often find cases where the rules are 
considered obvious to drivers and the speed limit isn't high enough to 
warrant the additional cost of regulatory signage. But that shouldn't 
change how we use tags like junction=roundabout that significantly 
affect guidance instructions.

-- 
minh at nguyen.cincinnati.oh.us