self propulsion at idle

Hard to put a subject title to this so I'll do my best to describe it. Perhaps I'll mention it at my next service if I can get some clarification from others who have experienced it.

I've noticed it happen a few times in the 15000km of driving my v.

I first thought it was unique to a cold start but last time it happened was after 30 minutes of driving on the highway, then stopping in traffic. Happens with the ICE running or not.

So normally when coasting to a stop with foot off the pedals, the HSI shows 1 pip on the charge bar.
With foot off the pedals in rush hour traffic at very low speed the HSI normally shows zero charge and zero power, no pips, idle position, right?
So what I've noticed happens sometimes, while moving at very low speeds, in a lineup of cars moving along slowly with occasional stops, when I lift off the brake the HSI shows 1 pip above idle, no foot on the gas pedal and the car moves along on its own with only having to feather the brake to control speed(I'm not talking an out of control runaway prius, more like walking pace and only on a completely flat surface). It actually functions well in stop and go heavy traffic situations where it has happened as i don't need to be constantly shifting back and forth brake/gas brake/gas to move ahead a few feet in line.

Normally on most occasions such as waiting in a drivethru lineup after sitting for a few seconds, on releasing the brake pedal I usually have to push on the gas pedal to move the car at all, it will just sit and not move on a flat surface with no foot on the gas or brake. Come to think of it self acceleration from idle seems rather random, sometimes the car will roll along on its own, other times it will roll back a bit if on a bit of a hill, good thing for the hill start assist!

So I'm wondering, is this a feature or does the HSD just get confused sometimes causing idle position to be slightly different under varying temperatures and driving conditions? Extreme cold could be a factor, as far as I can remember, it has usually been very cold whenever this strange idle behavior has happened. Perhaps it is just the nature of the HSD, at times it almost feels like a living thing with a mind of its own.

 

Ah, yes that's the word I was looking for, "creep". That one word may have saved everyone who came in here from having to read my long winded original post.
Basically I noticed the amount of "creep" is not always perfectly consistent. Sometimes it feels like the cold start "high idle" effect you would get in a non-hybrid automobile where you would get an extra boost of "creep power" till the engine settled down.
Perhaps the Prius tries to "simulate" the high idle effect as it does other drive-train features from normal cars such as engine drag while coasting.

 

Just did a search for prius idle creep and found this thread among others: Disable Idle Creep! | PriusChat

I guess this subject has already been discussed many times over, sorry for beating, yet again, the old dead horse.