I drove from Perth to Stirling on Friday, then back up on Sunday. Both unpleasant journies, to be honest.
I do this journey a lot. The route is dual carriageway all the way, so 70mph limit, and has average speed cameras the full length. I'm not a particularly slow driver - I used to speed more than I should, but now I have my baby in the car with me I am more careful. I tend to stick to the speed limit (if conditions allow) and maybe sometimes I creep up to 75, realise and slow down again.
So on Friday I was driving at 70, the road was busy and we entered a section of road which had a temporary limit of 40 mph. There was no apparent reason for this - I assume that this is in anticipation of roadworks as this is very common on that road, but there was no signage or cones to indicate this.
So I duly slow to 40. I didn't slam my foot on the brake, I took my foot off the accelerator and gradually decreased my speed. However I immediately found that every other car around me was paying absolutely no heed to the new limit, and were haring past me at 60-70. I was getting overtaken by lorries and quickly decided that my 40 was dangerous as I simply wasn't keeping up with the flow of the traffic. So I sped back up to 60. This is not the first time this has happened to me on that road. I don't know if the average speed cameras a calibrated to include the temporary limits, I guess we will soon see 
On the drive back on Sunday, I simply found that every single time i pulled out to overtake someone, I had some arse sitting on my tail within 30 seconds, like I had no right to be there. Honestly - almost every time, and I was doing 70! I also don't hang around in the overtaking lane so it's not that I was there too long or hogging it. It was really stressful by the end!