Roads

Expressed in billions of passenger-kilometres, road transport accounted for 87% of domestic passenger transport in France in 2008, 82% of which was by private car, compared with :

• 11% for rail transport ;

• 1.5% for air transport.

In freight transport, the road share, expressed in tonne-kilometres, is 86%, compared with :

• 12% for rail ;

• 2% for river transport.

These major imbalances between modes of transport, which are also found in many other countries, are mainly due to the great flexibility offered by road transport, which is the only mode capable of providing door-to-door solutions.

Even if the current situation is generally considered unsatisfactory, as we move towards a gradual reduction in fossil fuel resources and growing concerns about the increasing greenhouse gas content in the atmosphere, roads are currently – and will be for a long time – a very heavy component of the world's transport systems, just as they represent a very significant item in public budgets.

It is therefore important to :

• get the best service from road networks;

• ensure durability to reduce maintenance and renewal costs;

• and, at the same time, limit their impact on the environment and reduce the consequences of the scourge of road insecurity.

Each of these points will be the subject of separate articles.

The purpose of this article is to :

• briefly review the history of road network development;

• describe the current situation and institutional environment ;

• recall the technical fundamentals common to all aspects of road and pavement design, particularly those resulting from interactions between roads and vehicles.

Particular emphasis will be placed on the serious problem of road unsafety, which should always be at the heart of road engineers' concerns, as well as the vast problem of road-environment interactions, which will not be addressed here.