Sayyiduna Ubadah bin al-Samit (may Allah be pleased with him) says that the judgement of the Messenger of Allah (peace and blessings be upon him) concerning an open space (beside a road) is: "When its owners wish to build on it, they should leave seven cubits of it for the road." He said: Those roads were called al-mita'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب إحياء الموات / 11863