K27:
A lot of car drivers increase their speed as soon as you place the O/S indicator on
I strongly suspect it’s because cars don’t like being forced down to 56 ish when they can do 70.
This tends to happen when something known as “a begging signal” is misused and tends to have taken over from the correct procedure
of changing lane. It does not help with most vehicles travelling far too close to each other.
But it seems to be the way these days. Make your own rules up and blame everyone else.