The National Roads and Motorways in Greece constitute the main road network of the country. These two types of roads are distinct in terms of their construction specifications. Their main difference is that motorways (Greek: Αυτοκινητόδρομοι) adhere to higher quality construction standards than National Roads (Greek: Εθνικές Οδοί).
For example, a typical motorway (highway) in Greece consists of six or four lanes (three or two lanes in each direction) plus an emergency lane, separated by a central barrier. Entrances and exits to the motorways are only provided at grade-separated junctions (interchanges) and there are no traffic lights. Greek motorways are generally organized so that the odd-numbered motorways are of north-south alignment and the even-numbered motorways are of east-west alignment. However, there are many exceptions.