When you search for directions using Google Maps, there are a variety of factors at play in determining when you’ll actually arrive, according to a former Google engineer.
In a post on Quora recently spotted by 9to5Mac, ex-Google engineer Richard Russell reveals more of what that is:
“Like in similar products, Google maps ETAs are based on a variety of things, depending on the data available in a particular area. These things range from official speed limits and recommended speeds, likely speeds derived from road types, historical average speed data over certain time periods (sometimes just averages, sometimes at particular times of day), actual travel times from previous users, and real-time traffic information. They mix data from whichever sources they have, and come up with the best prediction they can make.
Most companies who do live traffic compare their predictions against actual time in traffic to tune their algorithms and data sources. The likely result of this is that the companies who have access to the best usage data (ie those who are best able to compare their predictions against reality, which means those who have the most usage) are likely to end up with the best predictions in the medium to long term.”
In short, there’s a ton of data Google is calculating just to tell you that your destination may happen to be 10 minutes away. The company also revealed more on how crowdsourced traffic data helps make Maps even more accurate in 2009.
“When we combine your speed with the speed of other phones on the road, across thousands of phones moving around a city at any given time, we can get a pretty good picture of live traffic conditions,” wrote Dave Barth, product manager for Google Maps.
Of course, no matter how much data is involved, the time you get will likely never be perfect. As Russell writes, calculating ETAs “is a future-prediction problem, and traffic, while it follows certain patterns, is inherently unpredictable.”
Google may know a ton of information, but it doesn’t know about the car crash that may have just happened or the school bus making multiple stops in front of you.