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CHAPTER FIVE
COMBINED-USE ROAD TUNNELS--LITERATURE REVIEW
Every tunnel is unique. This chapter shows how complex COMBINED USE FOR ROAD VEHICLES
tunnels can be. Considering the significant cost of tunnel AND UTILITIES
construction, there is a reasonable attempt to use tunnels for
Combined tunnels for road vehicles and utilities can include
different purposes.
gas and fuel lines. These types of tunnels cross rivers and
connect islands and even possibly continents. When finished,
The combined-use road tunnels can be classified as follows:
the Bering Straight Tunnel will contain a highway, railway,
oil pipelines, and fiber optic cables. The installation of oil
· Combined use for road vehicles and pedestrians and
pipelines could lead to additional risk that would need to be
bicycle riders.
addressed when designing for a fire.
· Combined use for road vehicles and utilities, including
gas fuel and electrical power lines.
· Combined use for road and railway vehicles. COMBINED USE FOR ROAD
· Railway tunnels with railway cars that carry road AND RAILWAY VEHICLES
vehicles. A channel tunnel is an example. This type of
tunnel is considered a railway tunnel and is not covered There are many examples of combined use for road and rail-
by this report. way vehicles in tunnels (see Figure 7). Some tunnels have
separate tubes for road traffic and separated tubes for railway
traffic. Some of them have a single tube that serves for both
COMBINED USE FOR ROAD VEHICLES road and railway traffic. An example of this is the Whittier
AND PEDESTRIANS Tunnel in Alaska. This 4-km (2.5-mile)-long, one-lane tunnel
was designed as a combination highway and railway tunnel
Tunnels for combined use can be classified as follows: that allows cars and trains to take turns traversing the tunnel.
It is the longest combined railhighway use tunnel in North
· Tunnels with pedestrian walkways and bicycle lanes. America.
The Stockton Street Tunnel in San Francisco is an
example of this type of tunnel (see Figure 5). Most of Drogden Tunnel between Copenhagen in Denmark and
these tunnels are relatively short. Such tunnels require Malmo in Sweden is an example of the combined-use tunnel
special attention for air quality and security. Some with separate tubes for road and railway vehicles (24). It is an
road tunnels allow for animals to pass through under immersed tunnel approximately 4 km (2.5 miles) long. Com-
supervision. pleted in 2000, it consists of two uni-directional rail tunnels
· Tunnels that accommodate bus stops (see Figure 6). and two uni-directional road tunnels. All four tunnels are
Passengers occupy the Stop area only and do not travel parallel. Between the two road tunnels there is a very narrow
along the tunnel. This bus tunnel in Seattle is an exam- tunnel, or "central gallery," which runs the length of the tunnels.
ple. Since 2009, a downtown Seattle Transit Tunnel has The central gallery consists of three smaller "galleries," one
allowed bus and rail. There are many regular road tun- on top of the other. At the top is a "service gallery," below
nels that allow for any traffic and accommodate bus that is an "escape gallery," and below that is a small gallery
stops leading to the outside. Those tunnels may require for fire mains and drainage pipes (see Figure 8). There are
special attention to public safety as they are similar to cross-passages between the road tunnels and the narrow
railway and metro tunnels dealing with higher concen- tunnel. Incidents occurred in these links in 2000, 2001, 2004
trations of people in the tunnel. However, this could be and 2007, but none in the tunnel itself. There is presently no
more dangerous from a fire standpoint owing to the pos- available information on tunnel fires occurring in combined-
sibility of truck fires. use tunnels.
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FIGURE 7 Whittier Tunnel interior: combined-use for road and
railway vehicles.
FIGURE 5 Tunnel with pedestrian walkways all along
the tunnel for pedestrian crossings (San Francisco).
FIGURE 8 Cross section of the Drogden Tunnel (dimensions in
millimeters).
FIGURE 6 Tunnels that accommodate bus stops (Seattle).
