Could be very unsafe if this kicks in unexpectedly during an overtaking manoeuvre on a single carriageway. Less speed during the overtake is less margin to oncoming traffic (more time spent in the oncoming lane), and a small speed difference can have a big effect.

Edit: another comment mentioned merging- this too can be huge. If your car isn't keeping up with the flow of traffic, or unable to move faster, that could also directly cause accidents if there's a space in front but no space behind.