What is the most common threat to the roads of the UK and what would be the solution to such a problem?

Question: What is the most common threat to the roads of the UK and what would be the solution to such a problem?
- Keywords:
  road,
  solution,
  threat,
  UK
Asked by Kim_Kardashian to Philippa on 16 Mar 2015.
- Philippa Jefferis answered on 16 Mar 2015:
  
  We are currently reliant on quite old infrastructure. A lot of our bridges were built quite a while ago. In particular, a number of roads that were built in the 1960s were built using reinforced concrete (steel bars embedded into the concrete to give it more strength in tension). However, concrete is porous (has lots of little holes in it) and when we have used de-icing salts on the road and then this has been washed away with melting ice, the concrete has started to absorb this salty water. The result is that a lot of our bridges are starting to fail because the steel inside has been corroded by the salt water seepig into the concrete.
  
  Currently the solution is to replace big sections of road impacted and put in proper drainage to stop water getting into the concrete. However the next big improvement would be to find an alternative way to protect the concrete or use completely different material that wouldn’t be impacted by de-icing salts.

Question: What is the most common threat to the roads of the UK and what would be the solution to such a problem?