About 7,600 miles were nationally maintained and included the greater portion--5,200 miles--of those in the modernized, improved category. Only about 1,400 miles of the local roads were modernized, and less than one-half of them had hardened surfaces. According to government planning reports, the road network is considered adequate in size, and all that can be allocated to it will be applied to its modernization. Motor transport was nearly negligible until after World War II, but between 1950 and 1969 it assumed importance that rivaled the railroads in both cargo and passenger traffic. Waterways Nearly 1,500 miles of the rivers are considered navigable. All of the Danube--over 900 miles--that is within or along the southern border of the country is navigable and, in fact, connects the Black Sea and Romania with all points upstream--through Yugoslavia, Hungary, Czechoslovakia, and Austria to Ulm in West Germany. The Prut, flowing along much of the eastern border with the Soviet Union, accounts for most of the remaining navigable mileage. Other streams are useful in some degree for timber rafting and for floating agricultural products downstream. Rapid currents in hilly sections, silting and meandering streambeds in the lowlands, and fog and ice in winter months, however, limit the commercial usefulness of the rivers. Ice stops traffic on the Danube River for an average of more than one month per year and on the other streams from two to three months. The country's topography does not lend itself to the development of an extensive system of canals. There are short canals in the western lowlands. Two of them connect to the Tisza River in Yugoslavia but, as with this pair, further development of the waterways in this portion of the country would be economically advantageous only when they connected to points in Hungary or Yugoslavia. Most of the northern and central regions are hilly or mountainous. Cargo shipped on rivers and canals in 1969 was less than 1 percent of that carried by the other transport systems, but most of it was transported for relatively long distances along the Danube River. Passengers carried constituted an even more minute percentage of the total and, because the largest numbers of them rode river ferries, the relative passenger mileage percentage was even lower. Airlines