You need the width of each lane. 1 mile is 1.609km approx. or 1609.34m.
If the fixed width of 1 lane is w, then the area occupied by one mile-long lane is 1609.34w sq m. For 4 lanes it's 4 times this=6437.38w sq m approx. If w = 4m then this comes to 25749.5 sq m.