▁has ▁issued ▁what ▁it ▁calls ▁the ▁“ AST M ▁Standard ▁Spec ification ▁for ▁Imp act ▁Att enu ation ▁of ▁Sur face ▁Systems ▁Under ▁and ▁Ar ound ▁Play ground ▁Equ ip ment ”, ▁which ▁is ▁known ▁by ▁its ▁numerical ▁design ation , ▁F 1 2 9 2 . ▁This ▁standard ▁accounts ▁for ▁both ▁the ▁dec eler ation ▁of ▁the ▁head ▁during ▁impact ▁and ▁the ▁length ▁of ▁time ▁the ▁head ▁takes ▁to ▁stop ▁moving . ▁The ▁test ▁sim ul ates ▁the ▁impact ▁of ▁a ▁child ’ s ▁head ▁hitting ▁the ▁surface ▁from ▁various ▁height s ▁of ▁the ▁play ground ▁equipment . ▁ ▁Access ibility ▁In ▁the ▁United ▁States , ▁as ▁well ▁as ▁being ▁safe , ▁a ▁play ground ▁surface ▁should ▁be ▁firm ▁enough ▁to ▁meet ▁the ▁requirements ▁of ▁the ▁Americans ▁with ▁Dis abilities ▁Act , ▁which ▁means ▁it ▁must ▁offer ▁easy ▁mob ility ▁for ▁children ▁in ▁wheel ch airs . ▁Me eting ▁these ▁dual ▁object ives ▁limits ▁the ▁number ▁of ▁types ▁of ▁surfaces ▁that ▁can ▁be ▁considered ▁by ▁responsible ▁play ground ▁owner / oper ators . ▁A ST M ▁International ▁has ▁developed ▁test ▁method ▁F 1 9 5 1 ▁to ▁evaluate ▁comp liance ▁with ▁the ▁Americans ▁With ▁Dis ability ▁Act ▁( AD A ). ▁However , ▁meeting ▁the ▁A DA ' s ▁requirements ▁does ▁not ▁guarantee ▁that ▁all ▁children ▁with ▁dis abilities ▁can ▁use ▁the ▁play ground ▁equipment . ▁ ▁As ▁the ▁table ▁above ▁makes ▁clear , ▁some ▁surfaces ▁commonly ▁used ▁do ▁not ▁provide ▁ade qu ate ▁protection ▁from ▁the ▁effects ▁of ▁falling , ▁or