Interesting. Your experience is evidently different from mine: I don't generally find it at all stressful if a car is waiting behind me. In fact, usually I appreciate it because I know that usually it means the driver is being considerate and not trying to overtake at a point where it's dangerous to do so. And figuring out with more certainty why they are holding back isn't usually much of an issue. I don't find glancing back difficult - at least enough to see roughly where the car is and whether it has indicators flashing - and I often have a mirror anyway. And even without looking back, I can often hear roughly what kind of vehicle it is (car, bus, etc.) I already know the road conditions - whether overtaking would be safe, whether I'll need to pull out in a few seconds, which the driver behind may well have also noticed. And I also know whether there's a side turn or something coming up that the car may be wanting to turn into - so I
already know the likely reasons why a car or other vehicle could be waiting behind me. And usually, if my quick assessment tells me that I'm likely to be holding the vehicle up for more than a few seconds, I will look for a safe place to pull in slightly to let him/her past and gesture my intentions - which often (though not always) attracts a wave from the driver, or a thank-you light-flashing from the bus driver. (Bus drivers in London are btw usually exceptionally good at indicating a thank-you - far more often than any other group of drivers in my experience. But I'm really going off-topic and getting too gossipy now aren't I
)
On the other hand - a car that comes up at speed and overtakes too near/too fast/when it's not really safe - fpr me, that
is stressful. (
Note to other cyclists - it's also stressful when cyclists come up and overtake too near - especially when they do it on my left. And downright annoying if I'm slowing down for a pedestrian crossing that someone is obviously waiting at, and they
still overtake).