-- Page 211 --
Effects of a Geographical Constraint on a Runway's Declared Distances
A runway's RSA begins a set distance prior to the threshold and will extend a set distance beyond the end of the runway
depending on the runway's design criteria. If these required lengths cannot be achieved, the ASDA and/or LDA will be
reduced as necessary to obtain the required lengths
to the extent practicable.
Airport Operations 4-3-11