Do you ever wonder how Google Maps comes up with an ETA for your trip? It's not as simple as crunching the speed limit and the distance, though those are two of the factors. A former Google engineer explained what goes into the company's algorithm.
Google is limited by what data is available for different roads, but the figures it uses include "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."
That's got to be one hell of an algorithm. While it's impressive, the engineer also notes that it'll never be perfect. After all, there's always an accident waiting to mess up the ETA or, you know, someone's day/life.