Amava okusebenza okuphuculweyo, amaxesha okusebenza awandisiweyo, ukhuseleko olungenakuthelekiswa nanto, kunye nokunciphisa iindleko zokulondolozwa kunye nezisombululo zethu zamandla ezishukumisayo kwizithuthi ezinesantya esiphantsi (kubandakanywa neenqwelo zegalufa) kunye nezicelo zemizi-mveliso (kubandakanywa iiforklifts, amaqonga okusebenza emoyeni, kunye noomatshini bokucoca umgangatho) . Bandakanya kodwa ungaphelelanga kwezi modeli zilandelayo: