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Comment by dewitt | Hacker News Reader

"Road directionality" being only 98.9% accurate seems to be a huge problem for a navigation app!

Road directionality is variable over time. I'm not sure at what rate it changes but I bet it's a lot more than 1.1% per year.

Hmm, I’ve seen maybe a handful of two-way streets change to one-way over my entire life, and have never seen a one-way street change direction. If ~1% of streets changed direction every year, there’d be mass confusion and frustration.

One major thoroughfare in London changed (if I remember right) from one-way in one direction, to one-way in the other direction, to two-way, in the space of a couple of years.

People got used to it very quickly, to the extent that they would not remember the change ever happened.

If you have a broad enough roads to have two-way streets everywhere, there's little motivation for it to change. [Edited to note: at the level of individual cities, OSM's directionality was often estimated to be 100% correct]

But, with some narrower one-way streets, there becomes a clear motivation to tweak things to improve traffic flows (and also tweak the surrounding two-way streets).

Mapping OSM in NYC, I've run into about a dozen one-way streets that have changed direction at some point, sometimes for just a block or two.

There’s apparently a trend of converting one-way streets to two-way; cities have realized that one-way streets are a little too efficient, they increase bandwidth but often cities want you to stop and shop.

Indianapolis has been moving that direction, at least, but I don’t know how widespread it is.

Im yet to read TFA, but I could foresee there being plenty of one-way private drives and parking lots - if not included in the study, I tend to agree with you

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