Standards and Recommended Practices. In ICAO language this means shall or should.
So in relation to RESA, the standard is 90m and the recommendation is 240m.
Some states take the recommended value as a requirement although often permit a distance between 90 & 240 if an aeronautical study shows the risk has been reduced to as low as reasonably practicable.
A cursory glance at some rejected take off overruns seems to point at 240m as a norm not 90m.
One area that needs addressing is aircrew electing to stop at either V1 or just above. The Brussels Kalitta 747 is a case in point. Does it suggest that some crew are so concerned that they prefer an overrun to exporting the problem into the air?
SGC