The core idea is that, when people ask for directions from A to B, it shows that people are interested in B, especially if they happen to be at or near A.
Now, certain very large search engines have massive logs of people asking for directions from A to B, hundreds of millions of people and billions of A to B queries. And, it appears this data may be as or more useful than user reviews of businesses and maybe GPS trails for local search ranking, recommending nearby places, and perhaps local and personalized deals and advertising.
From the paper:
A query that asks for directions from a location A to location B is taken to suggest that a user is interested in traveling to B and thus is a vote that location B is interesting. Such user-generated direction queries are particularly interesting because they are numerous and contain precise locations.What is really cool is that, not only is this data easier and cheaper to obtain than customer reviews, but also there is so much more of it that the ranking is more timely (if, for example, ownership changes or a place closes) and coverage much more complete.
Direction queries [can] be exploited for ranking of places ... At least 20% of web queries have local intent ... [and mobile] may be twice as high.
[Our] study shows that driving direction logs can serve as a strong signal, on par with reviews, for place ranking ... These findings are important because driving direction logs are orders of magnitude more frequent than user reviews, which are expensive to obtain. Further, the logs provide near real-time evidence of changing sentiment ... and are available for broader types of locations.
I find it a little surprising that Google hasn't already heavily been using this data. In fact, the paper suggests that Google is only beginning to start using it. At the end of the paper, the authors write that they hope to investigate what types of queries benefit the most from this data and then look at personalizing the ranking based on each person's specific search and location history.