Present And Near-Term Potential In Applying Weather Information To Improve The Highway System: Position Papers Page: 3
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However, if we had a perfect weather forecast, do we have perfect processes? Whether an
agency practices anti-icing or de-icing, the ability for a chemical to work effectively depends
upon the ability for the road to hold and to retain that chemical. Chemical retention depends
upon numerous road conditions such as road surface, road structure, road profile and road
material, in conjunction with vehicle volume and vehicle speeds. Assuming road structure
remains fixed from one winter event to the next, then the variables are time of chemical
deployment, amount of chemical, vehicle speeds and vehicle volumes. The faster cars travel and
the more vehicles there are, the greater the amount of chemical, which is splashed into the air or
onto the shoulder of the roads. Vehicle detection systems can be used with RWIS and data could
be correlated to measure the effects of vehicle to chemical retention. Possibly, RWIS systems
need to be outfitted to measure "splash" as well. The other difficulty for anti-icing is that both
passive and active sensors do not measure the amount of de-icing chemical. The measurement of
freeze point is based on the percentage concentration of the chemical. Therefore, in anti-icing
operations, whether 500 gallons or one gallon of 20% salt brine is deposited on the same stretch
of roadway, the measured freeze point is the same prior to precipitation. For effective anti-icing
operations, a measurement of the amount of chemical retained on the roadway would be useful.
Today, this type of sensor is not available.
Highway system decision makers are typically from Maintenance, Traffic, or Operations The
other decision makers are the users of the highway system, the driving public. Depending on the
information each requires, the communication media is different. Pavement forecasts are
delivered today via the Internet, fax, pagers and cell phones. From an Intelligent Transportation
Systems (ITS) perspective there has been a movement to providing weather data over a variety
of mediums like the Internet and 511 telephone systems. However, I believe there needs to be a
greater coupling between maintenance operations and ITS. For example, within ITS, many
transit authorities track buses with transponders or GPS systems so that they know where the bus
is on the route and then provide customers at the bus stops information on exactly when the bus
will arrive. Also, almost every transit authority publishes their bus schedule on the Internet. As
a driver, I always feel relieved if I am driving on the road after the snowplows have cleared the
road. It would be useful to have snow clearance routes published on the Internet with real time
snowplow location information. One of the barriers to effective winter maintenance is vehicle
congestion which blocks the roads and prevents the snowplows from accomplishing their task. If
drivers knew when the roads were cleared, they may wait at their offices or homes until after the
plowing and there would be fewer cars congesting the snow routes. Another lesson from transit
authorities is the use signal prioritization, a system where buses communicate to the upcoming
traffic signal to change the signal to green. The City of Los Angeles has outfitted their transit
buses with transponders located on the bottom of the buses. The inductive loops in the road read
the transponder and alter the traffic signal timing upstream of the bus. Obviously, since
snowplows are most effective when they are moving, this type of prioritization increases their
effectiveness.
Another ITS tool is ramp metering systems. Ramp metering regulates the volume of vehicles
entering the freeway network to reduce congestion. Many of the algorithms which, regulate the
number of vehicles, are based on lane occupancy, volume and speed or a combination of these
parameters. Empirical data has shown that weather events can reduce the capacity of the
roadways by 25% or more since drivers increase follow distances and slow down. Driving on a
snow-laden road has different characteristics from a dry road and new ramp meter algorithms for
varying weather conditions need to be developed. In conjunction with Ramp Metering, there is
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Atmospheric Policy Program American Meteorological Society. Present And Near-Term Potential In Applying Weather Information To Improve The Highway System: Position Papers, text, November 4, 2004; Washington, DC. (https://digital.library.unt.edu/ark:/67531/metadc11882/m1/19/: accessed July 15, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .