Is this the only blue flag rule?
NDR Sporting Code
IV.Flags
4. Blue
a.
Used as a warning to a slower car that a faster car is approaching. Use caution. Hold your line, and make no moves to impede the faster car.
Surely I'm missing some?
I presume the above rule is used in-conjunction with...
VI. Overtaking1.
Overlap
a.
When overtaking a car, you must achieve any measure of overlap with the car you are overtaking in order to have the rights for that corner.
b.
“Any Measure of Overlap” is defined as the front of the overtaking car being level with or beyond the rear quarter-panel of the overtaken car (for tin-tops) or rear wheel (for single-seaters).
c.
This measurement is taken at the normal turn-in point.
If these are the only rules that apply ,I think more detail is required or clarification