Is there a test for "can i stop within my view?"

[Peng]

More of a theory point than an answer to the OP.

I've always thought that there are two benchmark braking rates

a - a more gradual one chosen for comfort and car balancing. This will have a bit of a safety margin and used in most road driving.

b - Avoid an accident rate - maximised braking without thought for comfort.

When driving using limit points the braking speed should be the more gradual one with safety margin. If you do get caught in a situation then you should have some brake in reserve.

I'm lucky and have a roundabout near me with 300/200/100 markings. On a quiet day I can use these to judge the braking rate.

[quiraing]

Just drive. If it feels too fast and out of control then slow down before you crash (and we don't want that). If you feel you would still be in control if going faster and you want to go faster then go for it. Don't confuse your brain with braking ratios or recommended distances. Just drive.

[Promethius]

It's easy enough to find out if you can stop within the distance you can see to be safe - drive at your usual speed, - just be sure there is nothing remotely behind you - and slap the brakes on. If you cannot stop before reaching what was the limit of your vision, you were going to fast.

Anyone with a decent level of experience and cowardice should not even need to ask this question, much less put their judgement to the test . . .