@nprofile1q... Correct. I painted an 80km sign on the back of our van some 6 or 7 years ago, and have not breached that speed in that time. From my understanding most vehicles use 12-15% less fuel on the difference between 80 and 100 km, therefore, reduced emissions (and I save a few pennies).

By and large I have received very few examples of poor behaviour as a result. Sometimes people cut in front of me as they pass as obvious rebuke and I have received the occasional middle finger or toot on the horn. I remember back in the 70's when there were still many older slower vehicles on the road and they sported a 'slow vehicle' sign, other road users were able to accommodate that.

Don't wait for the signs to go up.