The Staggering Cost of Road Salt

[Rothman]

I know you've already read this, but...

As my bridge engineer friend put it:  If you could invent a non-chloride way of keeping ice off roads, you could save the world trillions of dollars.

Heating coils ftw

Saying it doesn't make it (a) practical or (b) cost-effective.  You think nobody thought of your idea before?

With extremely low cost solar power on the horizon, it will be cost effective

I'm sure solar power will work just fine during blizzards.

May we remind you of this 18th Century technology called the battery...

[kalvado]

I know you've already read this, but...

As my bridge engineer friend put it:  If you could invent a non-chloride way of keeping ice off roads, you could save the world trillions of dollars.

Heating coils ftw

Saying it doesn't make it (a) practical or (b) cost-effective.  You think nobody thought of your idea before?

With extremely low cost solar power on the horizon, it will be cost effective

I'm sure solar power will work just fine during blizzards.

May we remind you of this 18th Century technology called the battery...

A concept seemingly unknown to US and state  governments is "money".
You may do the homework yourself as I did, but a back of envelope estimate is couple hundred bucks per square foot of heated pavement assuming power comes free.

[Dirt Roads]

Roadway deicing capability is a requirement for the automated guideway transit (AGT) industry, and embedded heating elements have been used regularly for over 50 years.  Many AGT systems are operated as must-ride shuttles and loops with intense passenger loads (peak of 8,500 passengers per hour per direction or more).  These systems and the facilities they serve are completely dependent upon the deicing systems.  Depending upon the historic amounts of ice and snowfall in any particular part of the country, the amount of heating required (wattage per linear foot) can be high.  I've seen installations with thermal mesh rated as high as 45 watts per square foot. 

In northern climates subject to a lot of snowfall, the annual cost of electricity needed to heat the guideway can be as expensive as the annual cost of electric propulsion for the trains themselves*.  Thus, many systems only heat the areas underneath each path traversed by the tire/tiresets themselves.  Some AGT systems don't even bother having a full-width roadway because of snow/ice issues in the middle of each lane, but rather have a concrete plinth underneath each tireset (think dually trucks).

In addition to heating the guideway surface, a number of other elements may need to heated as well.  In our industry, it is common to heat power rails, signal rails, switch machines and guideway switch elements (some systems have crossovers using steel rails and standard railway switches even though the trains have rubber tires).  I've also seen heating applied to steel expansion joints and metal drains and associated downspouts.  Also, most systems have vehicles equipped with removal snowblades (think baby snowplows) on each wheel in each direction at the front and rear of every train.  Some vehicles are also equipped with heated deicing sprayers, but these are not generally on every train.

Most importantly, the goal is not to keep the guideway from icing over, but rather to keep the guideway from accumulating so much ice/snow that the guidance systems are impacted.  If we can keep the amount of ice down to a reasonable amount (say 3/8 inch = 9.5 mm), the trains/vehicles can keep operating.  Believe it or not, ice and snow actually have a pretty good coefficient of friction, except at the exact point of freezing (32^oF = 0^oC).  You can take advantage of this by controlling the activation of [expensive] guideway heating systems such that the guideway heating is only turned on when the temperature could be a few degrees either side of freezing.  It is my experience that automatic controllers have not been reliable when trying to limit the activation of guideway heating, so many systems prefer to keep the heat on until precipitation subsides and the controller decides to deactivate the heating elements.  Keep in mind that some of the stuff need other heating elements need to stay on whenever melting and refreezing can occur.

That is all so complicated to translate to a highway application.  However, it has been done in some rare instances.  Like everything in life, it is a math problem with an alternatives analysis.

Fun fact:  Back in the 1970s, WVDOH equipped all of the bridges on I-64 between Milton and Nitro with automatic controlled guideway heating.  [I believe that there were several different heating technologies being used, but I have no specifics].  This was intended to reduce the damage to the concrete surfaces and bridge structures caused by roadway salts.  It is my understanding that the experiment was successful, but the controllers needed frequent repairs and occasional replacements.  The DOH simply abandoned the heating elements in place.

[Road Hog]