Strada statale 4 Dir was built to make more fluid traffic between the province of
Rieti and Rome, taking advantage to the fact that, in that area, Via Salaria and the A1 motorway are very close () but divided by Tiber river. In fact,
SS 4 Dir allows to travel from Passo Corese to Rome entirely on fast-flowings roads, linking Via Salaria to the A1 motorway northbound branch (
A1 Dir) which is connected to
Grande Raccordo Anulare and, from this, to
Tangenziale Est of Rome. The alternative would be to use the
Strada statale 4 Via Salaria that is a single carriage highway, extending travel times and clogging up traffic. == References ==