1. Spatial constraints
A. Functions of wall
(1) Provide room for roadway at front of wall
(2) Retain roadway at back or top of wall
(3) Provide for grade separation, landscaping, or noise control
(4) Provide for ramp or underpass wall support
(5) Provide for temporary shoring of an excavation
(6) Ensure stability of steep side slope
(7) Flood control
(8) Serve as bridge abutment
(9) Other
B. Space limitations and site accessibility
(1) Right-of-way boundaries
(2) Geological boundaries
(3) Access of material and equipment
(4) Temporary storage of material and equipment
(5) Maintaining existing traffic lanes or widening