5 0 s , ▁along ▁with ▁Z ▁type ▁sal oon ▁carriage ▁stock ▁for ▁both ▁int ra ▁and ▁inter state ▁trains . ▁ ▁By ▁the ▁ 1 9 8 0 s ▁country ▁passenger ▁services ▁were ▁run ▁down , ▁and ▁older ▁wooden ▁rolling ▁stock ▁was ▁now ▁approaching ▁their ▁use ▁by ▁date . ▁As ▁a ▁result , ▁the ▁N ▁type ▁carri ages ▁were ▁introduced ▁from ▁ 1 9 8 1 , ▁followed ▁by ▁the ▁converted ▁H ▁type ▁stock ▁from ▁ 1 9 8 4 . ▁Since ▁then , ▁dies el ▁multiple ▁units ▁have ▁become ▁the ▁norm ▁for ▁new ▁purch ases , ▁with ▁the ▁Spr inter ▁introduced ▁in ▁ 1 9 9 2 , ▁and ▁the ▁V Loc ity ▁from ▁ 2 0 0 5 . ▁ ▁Fre ight ▁ ▁Early ▁w ag ons ▁were ▁built ▁on ▁four ▁whe e led ▁under ▁frames , ▁but ▁from ▁ 1 8 7 1 ▁bog ie ▁vehicles ▁begun ▁to ▁appear . ▁These ▁early ▁w ag ons ▁were ▁of ▁all ▁wood ▁construction , ▁but ▁later ▁types ▁had ▁wooden ▁bodies ▁on ▁steel ▁under frames , ▁then ▁followed ▁by ▁all ▁steel ▁w ag ons . ▁Gr oups ▁of ▁w ag ons ▁of ▁the ▁same ▁design ▁are ▁class ed ▁together ▁by ▁a ▁multiple ▁character ▁alphabet ical ▁code , ▁initially ▁in ▁a ▁system ▁restricted ▁to ▁Victoria ▁only , ▁but ▁from ▁ 1 9 7 9 ▁the ▁Rail ways ▁of ▁Australia ▁four ▁letter ▁coding ▁was ▁introduced . ▁Under ▁this ▁system ▁the ▁first ▁letter ▁represent ▁owner ▁of ▁the ▁w agon , ▁the ▁second ▁represents ▁the ▁general ▁type