Try this one......
Whilst driving on the motorway I often look at the signs giving distances to the next town.
I look at the speedo and do a quick mental calc of how long it will take us to get there, (or mile per minute).
Make a note of the time and thus your ETA.
Adjust the time if the motorway slows and update your ETA.
On arrival see how far out you were.
It passes the time anyway.......!