Explain how the safe distance tor travel by car is decided

It would be good to understand the basis for setting limits on the safe distance to travel by car. This would help improve compliance.
Details of how is science to used decide limitations on definition of what constitutes a ‘local travel’ are not clear.
Is say, a 40 mile journey in a car,to find a quiet place to go for a walk significantly more risky than a 10 mile journey?
What are the significant risks being considered? Is it likely that emergency services will be put at risk because of vehicle breakdowns? Is it considered that no safe arrangements can be had for parking and negotiating passage through gates etc.? Is it that any associated increase in economic activity produces too much risk ?
Is there something more than ‘It’s not a good idea to travel’
I seek more discussion on scientific evidence for how travel distance are set. It seems we rely on individual judgement.

Increased safe engagement in outdoor activity will improve the general health of people. Use of a car increases options for outdoor activity.
Compliance with safe practice is more likely if the basis for guidelines is better understood. I see little discussion on scientific evidence for how travel distance are set. It seems we rely on individual judgement.
The is also case for increasing economic activity associated with allowing more access to coastal regions.