If I’m at the back of a queue of traffic like that I keep the brake lights on and give myself loads of space in front to accelerate into if something is coming up a bit fast behind.
I was taught that, along with an extra tactic of controlling the traffic behind by slowing down early, this allows cars to catch up and join a mini queue of your own making at say 30mph, before you close up on the stationary queue and come to a halt. The instructor was an ex traffic cop. Works really well and I used it all the time now rather than just watching the traffic approaching and trying to work out if they are slowing down enough.
The other life saving bit of info…turning right across the centre of the road? Keep the wheels pointing straight ahead and only turn them when you start moving to enter the side road. Leaving the wheels turned across the oncoming traffic turns a simple rear end shunt into a shunt followed by a high speed side impact.