Two four-kilometer road tunnels are being built below the central area of the city, one for traffic to the north and the other for the traffic to the south. The two tunnels are about 20 meters below the surface and are 12 meters wide, providing for two lanes of traffic in each direction.
In the upper part of the tunnel, two air conditioning pipes remove the waste gas of trucks and cars and keep the quality of air inside the tunnel. The lighting is at the top of the tunnel, practically at its highest point. There will also be electric signs at frequent intervals. They show traffic conditions ahead and can be seen clearly by drivers. The wall is made up of four main elements, which include a waterproof covering and, on the inside of the tunnel, a concrete lining. Other systems in the tunnel will include emergency phones.
What is the main idea of the passage?A.The construction of two lanes. | B.The function of a road. |
C.The solution to cars’ pollution. | D.The design of two tunnels. |