What is the best design for roads and how can modern techniques prevent large delays and traffic build-ups?

Question: What is the best design for roads and how can modern techniques prevent large delays and traffic build-ups?
- Keywords:
  design,
  road,
  traffic
Asked by Sanchez to Philippa on 16 Mar 2015.
- Philippa Jefferis answered on 16 Mar 2015:
  
  Design is always dependent on local considerations. However something that we have been using is smart motorways, where we control traffic by limiting speed prior to a queue. When people brake hard they use up more space in the road as they do not stop as close to the car in front. However when we slow cars down progressively they don’t brake so hard causing blocks.
  
  Another way in which we are making the most of the road space we have is allowing cars to use the hard shoulder to drive on as well.
  
  However I think driverless cars would be a big part of getting rid of traffic jams as cars would be able to talk to each other and better manage the road space available.

Question: What is the best design for roads and how can modern techniques prevent large delays and traffic build-ups?