ocr: The railroads are an integral part of - the freight transport system, but have become unsafe through lack ofinvestment. North-south routes were intentionally left undeveloped under the Warsaw Pact.Ferries are usedf for most traffic across the Danube - inl 1989 there was only one bridge. Urban transportation is also lackang. Construction ofa subway for Sofia began in 1979.The first section has yet to be completed.
