"The Natural Philosopher" wrote

This is covered by the fact that driving within the limits of what you can
see/react to is considered correct driving, and failure to do so is
driving without due care and attention, at the least.
The fact of road being unrestricted does not mean it is safe or legal to
proceed at the maximum for that class of road. The one and a half car lane
past my house is a 60mph limit..few people exceed 40..


Thanks NP

3 points worthy of mention in response:

1 The slip road section in question gives the impression of being a
dedicated access to a busy A road, so even alert drivers could well miss the
fact that an (almost hidden) access road is ahead - will have to check the
signs, or lack of them, to see how clearly the side road is highlighted.

2 The party in most danger (ie the one that will suffer a side impact) is
not the one with the most control over the situation IYSWIM.

3 Your "driving within limits" point is noted, but considering what a
gamble it can be pulling out of this junction, many users must assume that a
road rated at 60mph is good for that speed (assuming clement weather).

Phil