▁high ▁containers ▁on ▁some ▁routes . ▁Tri als ▁were ▁made ▁with ▁the ▁ 4 D ▁double ▁deck ▁passenger ▁train ▁on ▁some ▁sub urban ▁lines , ▁requiring ▁alter ations ▁to ▁overhead ▁brid ges ▁and ▁structures , ▁but ▁no ▁double ▁deck ▁trains ▁are ▁used ▁today . ▁ ▁Sign alling ▁ ▁Comp are ▁with ▁Australian ▁railway ▁sign alling ▁ ▁Victoria ▁uses ▁a ▁mix ▁of ▁railway ▁sign alling ▁practices : ▁British ▁route ▁sign alling ▁with ▁home ▁and ▁distant ▁signals ▁( 2 ▁position ▁sign alling ) ▁and ▁American ▁speed ▁sign alling ▁( 3 ▁position ▁sign alling ). ▁ ▁Sem aph ore ▁signals ▁were ▁used ▁on ▁the ▁very ▁first ▁railway ▁lines , ▁but ▁only ▁a ▁bare ▁minimum ▁were ▁provided ▁as ▁the ▁time ▁interval ▁system ▁being ▁re lied ▁upon ▁instead . ▁The ▁first ▁inter lock ing ▁of ▁signals ▁to ▁protect ▁trains ▁was ▁provided ▁in ▁ 1 8 7 4 , ▁as ▁before ▁this ▁time ▁conflic ting ▁moves ▁could ▁be ▁made . ▁The ▁design ▁of ▁the ▁signals ▁also ▁progress ed , ▁with ▁the ▁disc ▁type ▁s iding ▁signals ▁first ▁introduced ▁in ▁ 1 8 8 5 , ▁and ▁the ▁lower ▁quadr ant ▁som ers ault ▁type ▁main ▁line ▁signals ▁adopted ▁in ▁ 1 8 8 7 , ▁both ▁of ▁which ▁are ▁still ▁in ▁use ▁today . ▁Green ▁was ▁not ▁adopted ▁as ▁the ▁All ▁Right ▁colour ▁until ▁ 1 8 9 8 , ▁with ▁white ▁being ▁used ▁before ▁this ▁time . ▁Red ▁was ▁the ▁usual ▁colour ▁of ▁all ▁signal ▁arms , ▁until ▁yellow ▁was ▁chosen ▁as ▁the ▁colour ▁for ▁distant ▁signals ▁in