The A 4 is a Portuguese motorway with a length of 63 kilometres (39 miles), running from Matosinhos to Amarante, where it narrows to become an IP road, signed as IP4 .
The motorway leaves the metropolitan area of Porto, through the urban areas of Ermesinde, Valongo, Paredes, Penafiel, until arriving at the mountainous town of Amarante.
It is also known as one of the most dangerous motorways in the country, particularly the descent from Campo to Valongo. Many improvements are being projected by the government in this respect.
Currently the highway has been extended into Bragança and the border with Spain, which opened in 2013, apart from the Túnel do Marão which will when completed be Portugal's longest road tunnel, cutting 5.6 km (3.5 mi) through the Serra do Marão. The extension will also include a bridge reaching a height above ground of 230 metres (750 feet). Once extended the A4 will become Portugal's third-longest motorway, with a length of 223 km (139 mi).