Why is there no emergency lane in the tunnel of the expressway?

Because parking is forbidden in the cave. This is the first. Generally speaking, even if the car breaks down, even if it is scrapped, it is very important to move the car out of the tunnel. The second is the construction cost. It costs a lot of money to widen the tunnel by two meters.

Tunnel is an engineering building buried in the stratum, and it is a form of human using underground space. The tunnel conference held by the Organization for International Economic Cooperation and Development in 1970 integrated various factors, and defined the tunnel as: "A cave with a cross-sectional area of more than 2 square meters, which was built underground for a certain purpose and in accordance with the specified shape and size by any method."

By category

1, according to tunnel geological conditions: soil tunnel and rock tunnel.

2. According to the tunnel length: short tunnel (railway tunnel: L ≤ 500m; Provisions for highway tunnels: L≤500m), medium and long tunnels (provisions for railway tunnels: 500).

3. According to the ITA definition, the criteria for dividing the tunnel cross-sectional area are: extremely small cross-section tunnel (2 ~ 3m2), small cross-section tunnel (3 ~ 10m2), medium cross-section tunnel (10 ~ 50m2) and large cross-section tunnel (50 ~ 100m2).

4. According to the location of tunnels: mountain tunnels, underwater tunnels and urban tunnels.

5. According to the buried depth of the tunnel: shallow buried tunnel and deep buried tunnel.

6. According to the use of tunnels: traffic tunnels, hydraulic tunnels, municipal tunnels and mine tunnels.