I was keeping a steady speed on cruise control on a weekend trip out of town this weekend, I was trying to maximize MPG just as an experiment. Two hours away, the AVIC was able to predict the time I'd pull into my driveway within one minute. By the time a bit of rain in Houston slowed traffic down a tad, about an hour and a half out, it nailed it to the minute.

8)

I have a Garmin Quest portable GPS and it can nail ETA times to the minute with great accurracy, and continually auto-adjusts for your current speed when you hit traffic congestion.

On a trip from Ottawa to London, I checked the ETA on my Garmin to my destination and it nailed it to within three minutes - we had clear sailing all the way. The time adjusted automatically for the two 15 minutes break stops we made. This was a 7+ hour trip.

I believe my Avic-D1 ETA is based on the distance from start to finish, taking into account the speed limits of the route and the selected speed settings in the setup, then adjusted with random number generation :?