Aeronautical Information Manual (AIM), page 211

Index   210 -- Page 211 -- 212

FIG 4-3-6
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

Page 211 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   210 -- Page 211 -- 212