Very short streets aren't really dead ends

[arnt]

Hi,

some cities are classified as very sprawling, even though that's not my impression on the ground.

One of the reasons is that very short streets are classified as dead-end streets. A street with just one house isn't really a dead-end street, or any street. It may be a postal address, but you cannot move anywhere on it because it's too short for movement.

I first noticed this in Rovigo, in Italy, but here's an excellent example on the outskirts of Dresden, Germany: https://www.sprawlmap.org/#15.9/51.04877/13.871918

Most of the ones I've noticed seem to be a result of infill. One or more buildings is built behind the first row, and a new "street" connects the new building(s) to the street network.

I think the correct way to handle these is to ignore "streets" shorter than about 20m when computing an area's sprawl index. Perhaps 30m.

Arnt

[cpbl]

Our algorithm considers pedestrian and cycling paths when computing connectivity of car streets.  We do not consider points that are only on pedestrian/cycling paths to be "destinations", and also do not render them on sprawlmap. This accounts for some of what you've reported, but we'll look in a bit more detail.  

 I hope you've found the "Satellite view" link under the "More" menu. I will also add one that links to the corresponding OpenStreetMap view to facilitate the kind of checks you're doing.

chris

[Adam Millard-Ball]

In addition to Chris' point, the existence of "short" dead ends is one of the reasons that we use multiple connectivity measures. So we measure the length of deadends as well as the fraction of edges that are deadends. And these short dead ends will also not affect our measures of circuity.

We were reluctant to use a cutoff like 20m, because the correct cutoff will vary by country. (In the US, there are some very long driveways!). 

However, most driveways are (or should be) tagged as "service" roads in OSM. Like pedestrians and bicycle paths, we include service roads in calculating the connectivity of an area, but we do not treat them as destinations. The Dresden example you raise is tagged as "residential road," not "service."