OVERRUN - cheers for the excellent info...
as regards grooved... while absolutely not doubting you, JAR ops subpart F, 1.480 (5) states that " A dry runway is one that is ......specially prepared with grooves or porous pavments, and MAINTAINED to retain EFFECTIVE DRY braking.
The later line being the key to it i guess.
appologies for resorting to quoting scripture (i mean JAR OPS), but your understanding of these matters far outweighs anyone elses