Why do we put salt on the roads when it snow?

Salt makes the snow melt right?  But why. Come on, now, you must have wondered this questions before.  Those big trucks come down the load and plowed as much snow and from the rear they are leaving salt mixture and magically you can drive on the road again.  But people always say, try to stay away from brigdges and over passes because those dangerous.  Why are bridges so dangerous?
It's actually pretty simple.The salt forms a brine on the roadway that melts the snow and ice. What is this brine a combination of moisture and salt.  As cars drive through this brine it breaks the bond allowing slush to form and then those giant plow trucks can do their job later and plow the slush out of way.  The bad new, the colder it is outside, the longer it takes for this process to take into effect. 

"Temperatures, time of application, weather conditions and the type of road surface, are among the many variables that can affect the success of deicing. For instance, at 30° F salt is five times more effective than at 20° F." Morton Salt assisted me in learning this simple trick.

The next topic, why are bridges more dangerous.  Road surfaces make a differience on the success of deicing.  Each surfaces absorbs heat differently.  Asphalt for example aborbs lots of heat.  That is with driveways that are pure asphalt, are easiser to clear out. However bridges are mostly built by steel and concrete not asphalt. There are two ways for heat to escape from above and below, while in road heats can only escape from above. Bridges do not absorb heat as fast making them less effective and having a less success for deicing.

I hope you learned a lot. So now that this new wave of snow came into my area.  I now know to avoid bridges and why I love salt on the roads, because I would rather drive on slush any day. Thank you for all those individuals who plow the streets of America!   

• Great site to learn more about why use salt on raods, check out: http://www.usroads.com/journals/p/rmj/9712/rm971202.htm