DH: How does a tunnel fare in terms of safety as compared to other roadway methods? Specifically, how would a multi-car accident resulting in a fire effect the safety of other drivers
GC: This is out of my area of expertise but I can share with you findings of my investigation on safety. Tunneling is not a new concept and it is very common in European countries and Japan. Tunnels are being constructed in Malaysia and Australia. Therefore safety issues/concerns have or should been addressed by all of the entities in charge of managing and operating roadway tunnels. Multi car accidents are probably not much different on an open road vs. a tunnel except the element of constrained space. I would think tunnels are safer than open on/off highways so, it would reduce the potential for crashes. Because of limited access traffic in tunnels can be managed more efficiently. The ability to control the flow of air/ventilation allows to take air away from fires and divert smoke away from people, i.e. divert smoke and toxic fumes towards the front of the crash where most traffic is cleared and away from behind where most traffic normally backs up. Many tunnels are provided with sprinkler systems as well as cameras. In addition tunnels provide for escape routes and alternative safety access (a smaller tunnel that parallels and connect to the main tunnels). The federal government has conducted studies on safety of roadway in particular for bridges and tunnels. Therefore, safety has been addressed at many levels.
DH: For those that may have arrived in the past hour, Houston is built on a variety of soil types and has a flat topography. How do tunnels deal with water or flooding?
GC: To my understanding the more homogeneous the soil conditions are the best for building tunnels even if the water table is high. Per Dr. Sauer coupled with a local geotech expert who was consulted on the soil and geological conditions of the I-45 corridor have indicated that Houston soil conditions are favorable for tunneling. One interesting item was discovered by Dr. Sauer during a trip to Spain while investigating new technologies and current tunneling projects. The following image is from Dr. Sauer's presentation for METRO. It shows a roadway tunnel currently being built in Malaysia. It incorporates a running stream at the base of the tunnel and the tunnel is design in such a way that will allow flooding of the tunnel to prevent up-stream flooding during the monsoon season - traffic will be stopped and water allowed to drain through the tunnel, once the flooding is over the tunnels will be washed and open to traffic.
DH: While on the subject of Houston’s environment, how do tunnels make the air cleaner?
GC: Many tunnels I have investigated use electro static
precipitation to filter air from the tunnel before it is sent outside.
Because of pollution from cars, tunnels are required to include air
circulation systems. Air purification is incorporated into the air circulation
systems. Depending on the air velocity up to 90 % of suspended solids
can be removed. Therefore, to my knowledge, roadway tunnels are the only
transportation type roadway alternative that allows air filtration.
DH: This aspect impresses me most. For once the relative
pollution count of a section of Houston is not dependant on wind, rain,
or congestion. I would also hazard a guess that the lower radiant heat
load a tunnel contains would do wonders for a summer commute and further
reduce drivers stress.
Mr. Camacho, I would like to thank you for your time and participation
and I hope that your plan receives the feasibility study that it deserves.
For more information visit www.camachoassociates.com
