Strategies for reducing vehicular accidents in thick fog|Earth Science – Geography
Introduction
Fog is a certain type of cloud that people occasionally encounter. While fog varies in
visibility and there are different types of fog as well, such as advection and radiation fog.
Although it might appear harmless, it can be a deadly hazard and creates dangerous road
conditions. When encountering, or driving through fog, it appears as a thick white cloud that
affects visibility. Every year fog causes large accidents that can be fatal due to the thickness of
fog. The California Department of Transportation has developed strategies in an effort to reduce
the number of fog-related accidents that occur each year with mixed results.
Types of Fog
According to the National Geographic, fog forms when water vapor condenses, during
which, molecules of water combine to form small droplets of liquid water that hang in the air.
This process allows fog to be visible. (“Fog”, 2014: 2024 – Essay Writing Service. Custom Essay Services Cheap). The different types of fog include advection
fog, radiation fog, valley fog and freezing fog. Radiation fog forms during the night when skies
are clear (Walker, 2003). The heat near the ground cools and then stabilizes which causes the
condensation of the water vapor and in turn causes the fog to form. In other words, the heat that
is absorbed by the surface during the day is then radiated into the air at night, causing the
condensation (“Fog”, 2014: 2024 – Essay Writing Service. Custom Essay Services Cheap). The skies must remain clear with minimal to light winds because
strong winds can prevent radiation fog from forming due to the mixture of air (Ahrens and
Samson, 97). There is also a type of radiation fog that occurs in the Central Valley called tule
fog. This fog is also known as valley fog. Tule fog forms due to the combination of cool air from
the Pacific, clear skies and light winds which all result in thick fog in the Valley from late fall to
early spring (“Fog Safety in Radiation Fog,” 2001). One of the ways radiation fog dissipates
occurs when sunlight pierces the fog and warms the ground which in turn warms the air (Ahrens
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and Samson, 98). When the fog is too thick and does not dissipate, it is known as high fog
(Ahrens and Samson, 98).
Advection fog forms when warm and moist air passes over a cool surface. The water
vapor condenses as the warm air touches the cold surface, such as cool ocean waters (“Fog,”
2014: 2024 – Essay Writing Service. Custom Essay Services Cheap). This fog is visible in the summer along the Pacific Coast (Ahrens and Samson, 98). If it
were not for advection fog, the redwood trees along the coast in California would have
difficulties surviving. (Ahrens and Samson, 98). This is due to the moisture in the fog getting
collected by branches which in turn waters the redwoods as the droplets drip down. Furthermore,
in order for advection fog to occur, winds are needed for the warm air to move over the colder
surface. However, for radiation fog, no winds are needed for the fog to form.
The North Pacific anticyclone, also known as the Pacific High, and coastal upwelling,
both combine to create prime conditions for fog to form in California during spring and summer
months (Gilliam, 2002). Cool air over an ocean surface is known as the Pacific High and it is
found between San Francisco and Hawaii (Gilliam, 2002). Upwelling is a process in which cold
ocean water surges to the surface (Ahrens and Samson, 78). The winds from the Pacific High
cause the ocean upwelling. As the air accumulates moisture, it stays still as a vapor and once it
encounters the cold upwelled waters, the vapor cools off to form small droplets by attaching
itself to small salt particles (Gilliam, 2002). Sea salt particles are hygroscopic nuclei which
means that the particles are water seeking (Ahrens & Samson, 97). Furthermore, as fog forms,
more droplets appear on hygroscopic nuclei that are available. Other types of hygroscopic nuclei
include pollutants which also cause fog to form in highways, airports and seaports (Hung and
Liaw, 268).
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Another type of dangerous fog is freezing fog. This type of fog is not frozen as long as
nothing is touching it. However, once it comes into contact with any object, the fog does freeze if
the temperature is below the freezing point of 32 degrees F (Shepard, 2017). According to the
National Weather Service, the water droplets in the freezing fog must be “super cooled” (“Fog
Safety in Freezing Fog”). Furthermore, this type of fog is particularly dangerous because it can
cause problems while driving or while in a plane because it will greatly reduce visibility. Trees
and branches become coated with ice. Furthermore, freezing ice can cause black ice on roads.
This type of ice is difficult to notice; therefore, it is best to use precaution when driving on icy
roads.
Foggiest Places in the US
Fog can form at any place as long as the conditions are in place. However, some places
are foggier than others such as the Golden Gate Bridge in California. Fog is known to envelop
the bridge making it completely disappear within the fog. The fog in San Francisco is advection
fog because of the warm moist air going over the cold waters of the Pacific coast. One of the
foggiest places in the United States is Mount Washington in New Hampshire. This area is known
to be foggy during 90% of summer days. In the winter, Mount Washington produces freezing fog
and visibility goes down to about 100 ft. (“Health & Safety Requirements”). Another foggy place
in the United States is Cape Disappointment in Washington. Cape Disappointment experiences
fog more than 100 days out of the year (Judd, 2014: 2024 – Essay Writing Service. Custom Essay Services Cheap). Point Reyes is another vastly foggy location
in the United States, near San Francisco in California. According to the National Park Service,
this fog can cover the ocean for over 50 miles off the shore and can completely cover the beaches
(“Weather”). Fog is the heaviest during July, August and September at Point Reyes.
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Fog-Related Accidents
Lack of visibility due to fog is the cause of many vehicular accidents. The amount of
damage fog can cause is comparable to the financial and human cost of storms like tornados
(Price, 168) This shows that fog is dangerous and can cause a lot of damage. Per Ahmed et al.
over 22% of crashes in the United states in 2001 were due to weather related visibility problems
such as fog. Between 2002 and 2007, Florida had 299 fatal crashes due to fog. Florida was also
among the top three states with the most crashes due to fog along with California and Texas
(Ahmed et al.) These findings are supported by a study conducted by Abdel-Aty et al. which
found that foggy and smoky conditions are much more dangerous than clear visibility conditions
(Abdel-aty et al.). These accidents occur like a chain reaction. One car will rear end one car due
to the lack of visibility and the oncoming cars will continue to crash into each other as they brake
too late. Every year pileups are reported across the country which shows that fog truly does
cause damage. Fog can also cover roads in patches which means that cars can be driving in clear
conditions and all the sudden their visibility drops.
Early in 2017, there was a fifty-car pile-up in Kings-County, California due to foggy
conditions (Johnson). The crashes continued along a four mile stretch of road, however, there
were no fatalities. On December 11th, 1990, heavy fog caused a deadly pile-up in Tennessee. 99
cars were involved in the deadly crash that left a dozen people dead (Lakin). This crash is known
as one of the deadliest crashes due to fog related conditions. In 2008 – Affordable Custom Essay Writing Service | Write My Essay from Pro Writers, four people were killed in a
70-car pile-up in Florida on Interstate 4. The fog had reduced visibility to the point where
rescuers had to walk from car to car, looking for injured people. The crashes and pileups
stretched out 15 miles through interstate 4. The New York Times also reported on a 100-car pile-
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up in Fresno that killed two people in November of 2007 (“100 Cars Collide on a Fog-Cloaked
Route”).
Strategies to prevent fog-related fatalities
The Department of Transportation has employed many strategies to reduce fatalities due
to fog. The California Department of Transportation, also known as Caltrans, is responsible for
managing state highway systems. In 1991, Caltrans and the California Highway Patrol (CHP)
began a program called “Operation Fog” (“Operation Fog”). On the website for Operation Fog,
there are 9 safety tips included for driving in foggy conditions. The first is to reduce speeds while
driving in order to have safe stopping distances (“Operation Fog”). Other tips include driving
with headlights on low-beam, avoiding busy intersections, and listening for oncoming traffic
(“Operation Fog”). Most of these tips are useful, however, avoiding busy intersections is not
something everyone can do, especially if they are trying to reach a specific destination and are in
a rush. The website also does not provide reasoning for the tips Caltrans provides. The public
should know why they are being told to follow tips. For example, using high-beams in the fog
will reflect the light back causing even worse visibility. Therefore, it is important to use low-
beams. Additionally, driving with open windows will allow one to hear the oncoming traffic,
even if it is not visible. The website also provides a video on fog safety. In the video, John
Castro, a transportation electrical engineer, explains that Caltrans has automated messages that
show up along strategic places along highways. These messages are triggered when visibility
falls below 500 feet and displays messages that warns drivers to slow down. This is a useful
strategy because it lets drivers know to expect fog and adjust their driving speeds. This would
benefit drivers who might not have been aware of conditions before going on the road.
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Caltrans also has a website titled “Fog University.” This interactive website also provides
tips on driving in fog, however, it also provides information on new fog technology, such as the
Fog Detection and Warning System (FDWS). According to the Department of Transportation,
tule fog is highly responsible for most weather-related accidents in California (“Best Practices
for Road Weather Management”). Therefore, Caltrans built the FDWS along a 13 mile stretch of
the California Highway 99. The system uses a combination of sensors and cameras and lets
drivers know about fog conditions and when to slow down due to traffic.
Having signs that alerts motorists of driving conditions saves lives. However, this could
potentially pose a problem if conditions are so foggy that the signs are not readable.
Additionally, even with these strategies in place large pile-ups still occur to this day. The Fog
University website lists that there were 46 fatalities, 1141 injuries, and 1503 collisions in
California (“Fog University”). It does not mention the year the statistics are from; however, they
show the sheer volume of damage fog can cause. However, there is only so much Caltrans can
do to prevent fog-related accidents. The only way to fully prevent accidents is to prevent drivers
from driving at all, perhaps by closing foggy roads and directing traffic through alternative
routes. However, that is not a feasible project as it would prolong driving times for those in a
hurry. People can choose to take alternative routes if they wish. The best Caltrans can do is offer
safety tips to the public. All it takes is for one car to make a mistake to set off a chain reaction.
Recently, mass text messages have been sent out to the public with severe weather alerts. These
messages guarantee that the public knows important weather events. This is especially beneficial
to people who do not watch morning news or do not go on social media. Nonetheless, Caltrans
has spread tips to a wider audience by utilizing social media. The Federal Communications
Commission (FCC) has done something similar by establishing the 511 system in 2000 (“511”).
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This traffic system provides real-time weather and traffic information. To access the 511 system
in California, the public can simply dial 511 on their phones to hear of current weather
conditions. They can also download the Caltrans smartphone app, Quickapp to look at weather
updates (“511 Traffic Systems”). There are also different social media accounts for certain
regions in California. The 511 system appears to be the easiest way to get information out into
the public the fastest.
Conclusion
Fog can vary in terms of types of fog and has varying levels of visibility. California
experiences two main types of fog, advection and radiation fog. Within California, the Central
Valley experiences tule fog from late fall to early spring. San Francisco is well known for the
advection fog that envelops the Golden Gate Bridge and is among the foggiest places in the
United States. Fog poses a deadly threat to motorists during foggy weather. Although there is no
way to get rid of fog, to combat fog-related accidents, Caltrans has developed strategies to
reduce these accidents with varying levels of success.
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