It is over 1,000 km long starting south of Barcelona and running predominantly along the coast to Chiclana de la Frontera and the N-IV to Cádiz.

It then heads along the coast to Tarragona, changing to the A7 until Cambrils, then crossing the River Ebro (delta) and on to Peníscola.

The N-340 re-emerges at Marbella and Puerto Banús and follows the coast south to Estepona where it joins the A-7 again to Algeciras past Gibraltar.

The Autovía A-381 takes most traffic west to Jerez de la Frontera through the Sierra Blanquilla.

On 29 August 2001 Binter Mediterráneo Flight 8261 (Registration EC-FBC) crash-landed adjacent to the N-340 near Ruiz Picasso International Airport at Málaga, Spain.

[3] The Autovía A-36 is an upgrade of the N-340 which provides a more direct (and toll free) route between Alicante and Valencia than the Autopista AP-7 which runs along the coast.