[rjmunro]

Or just "was this ride experience better or worse than your previous ride" for every ride apart from the first one you ever take. You could then use the Elo rating system to track driver scores.

[mg]

When every transaction is rated, the buyer will still get nagged by the seller to give them the star.

My thought behind giving one star to one of the last 3 rides is that the seller does not know when the buyer will give out that star. It might be 3 months in the future. So it seems futile to nag the buyer about what they will do then.

Calculating an ELO value should also be possible for more than two players.

[WithinReason]

Then you just say better, every time. It's the same problem as the 5 star system.

[rjmunro]

If anyone does this, their ratings will just average out to nothing. You could detect it and filter these people out.

You could reduce bias towards the most recent trip by adding a delay before asking.