▁$ 3 0 ▁and ▁$ 4 0 ▁respectively , ▁charged ▁both ▁directions . ▁The ▁normal ▁speed ▁limit ▁on ▁the ▁bridge ▁is ▁, ▁subject ▁to ▁lower ing ▁in ▁the ▁event ▁of ▁road ▁work ▁or ▁strong ▁wind . ▁Tra ffic ▁may ▁also ▁be ▁directed ▁to ▁the ▁shelter ed ▁carriage ways ▁on ▁the ▁lower ▁deck ▁when ▁there ▁are ▁very ▁strong ▁wind s . ▁There ▁are ▁no ▁pav ements ▁on ▁the ▁bridge . ▁ ▁Design ▁▁ ▁The ▁bridge ▁was ▁designed ▁by ▁M ott ▁Mac Donald . ▁The ▁firm ▁designed ▁an ▁early ▁iteration ▁of ▁the ▁bridge ▁in ▁ 1 9 8 2 , ▁with ▁a ▁two ▁l ane ▁dual ▁carriage way ▁on ▁the ▁top ▁deck , ▁and ▁a ▁light ▁railway ▁on ▁the ▁lower ▁deck . ▁The ▁bridge ▁was ▁red es igned ▁beginning ▁in ▁ 1 9 8 9 ▁to ▁account ▁for ▁the ▁three ▁l ane ▁dual ▁highway ▁and ▁the ▁heav ier ▁air port ▁railway . ▁The ▁design ers ▁were ▁inspired ▁by ▁the ▁For th ▁Bridge ▁in ▁Scotland ▁and ▁the ▁Se vern ▁Bridge ▁in ▁England . ▁ ▁Wind ▁tunnel ▁testing ▁ ▁The ▁object ives ▁of ▁the ▁wind ▁tunnel ▁studies ▁were ▁to ▁demonstrate ▁the ▁safety ▁of ▁the ▁structure ▁under ▁construction ▁and ▁once ▁completed , ▁both ▁with ▁respect ▁to ▁aer od ynamic ▁stability ▁as ▁well ▁as ▁the ▁possible ▁effects ▁of ▁extreme ▁ty ph oon ▁wind ▁spe eds . ▁A ▁further ▁objective ▁was ▁to ▁provide ▁dynamic ▁response ▁data ▁at ▁several ▁key ▁locations ▁to ▁compare ▁with ▁full ▁scale ▁data ▁from ▁the ▁on going ▁monitoring ▁program , ▁conducted ▁by ▁the ▁High ways ▁Department ▁of