By the early 1970s Portugal's fast economic growth with increasing consumption and purchase of new automobiles set the priority for improvements in transportation. Again in the 1990s, after joining the European Economic Community, the country built many new motorways. Today, the country has a 68,732 km (42,708 mi) road network, of which almost 3,000 km (1,864 mi) are part of system of 44 motorways. Opened in 1944, the first motorway (which linked Lisbon to the National Stadium) was an innovative project that made Portugal among one of the first countries in the world to establish a motorway (this roadway eventually became the Lisbon-Cascais highway, or A5). But, although a few other tracts were created (around 1960 and 1970), it was only after the beginning of the 1980s that large-scale motorway construction was implemented. In 1972, Brisa, the highway concessionaire, was founded to handle the management of many of the regions motorways. On many highways, toll needs to be paid, see Via Verde. Vasco da Gama bridge is the longest bridge in Europe.

What prompted transportation improvements in Portugal in the 1970's?