Slowly moving is much easier to a lot of systems than stationary. An easy way to distinguish a car from the guard rails or other fixed objects is to look at movement, most radar systems do this.
Very true, but I guess from a probabilities perspective, you're highly likely to encounter a stationary car in the driving lane (i.e. a badly parked car). I can't think of a time I've driven and not encountered this, and it's easy to react in advance before it was even a priority (see parked cars ahead, move out a lane, no inconvenience experienced...)
I wonder how it would cope with other items that don't "belong" in the roadway sitting stationary - skips, bins, shipping containers, large piles of bricks or rubble etc.
