To most people living in the UK, a pavement is the footpath at the side of a road. But in engineering terms it is concerned with applying man-made surfaces to the ground so that 'objects' (vehicles, people, animals) can move across it in an efficient and clean manner.
Any prepared surface for transport purposes counts as a pavement whether it's
- a 'dirt' road to a remote village in Central Africa
- a prepared ice surface to allow sledging of stores to an Antarctic research station
- a premiership football pitch
- a horse-racing course
- a path in your garden
What is pavement
engineering?
A dirt road in Africa 
A premiership football pitch 
A horse-racing course 
A garden path 
Of course some of the most important pavements are those which carry large numbers of vehicles such as
- motorways
- airport runways
- docksides
- railway tracks
M6 motorway, junction 10 
Runways 1L and 1R at San Francisco International 
Dockside in Olympia, Washington 
Railway tracks at Gatley Railway Station 
Most major soccer grounds, for example, have very carefully designed pavements which will drain easily to prevent them becoming too muddy. They must have enough 'give' to limit injuries to the expensive players, without being so soft that they sap a lot of energy. Other specialist pavements are to be found on tramlines, and between quarries and the processing plant.
A road pavement is a sequence of selected and processed materials placed on the natural ground, or "subgrade". In most cases the job of the pavement is to spread out the concentrated load of a vehicle so the pressure applied to the ground is much smaller than the pressure immediately under the tyre. A vehicle which would quickly bog down into muddy soil can cross the same muddly soil easily when there is a pavement in between. Each layer in the pavement is designed so that the stress it carries is smaller, but spread over a larger area, than in the layer above until the stress on the underlying soil is so small that the soil hardly notices that a vehicle is crossing it and doesn't rut.
The pavement engineer has the task of finding the right material and using the right techniques to build and then maintain the pavement. It mustn't be too expensive, it mustn't deteriorate too quickly, it should be as sustainable as possible, and it should be easily repairable. This isn't an easy job and requires a detailed knowledge of how each element of the pavement will behave under the repeated loading applied by the 'traffic' by itself and in co-operation with the materials in other parts of the pavement. Sometimes predicting the 'traffic' loading that the pavement can expect is one of the most difficult tasks. The pavement designer aims to get the most economical combination of pavement layers in which the capacity of each layer, or of the subgrade, is not exceeded during the design life of the road.
In the UK most pavements have "flexible" surfaces - i.e. they are surfaced with material that flexes slightly under traffic wheel loads. Usually the 'blacktop' that you can see is made of rock aggregates glued together by a black viscous mixture of hydrocarbons obtained as a residue from petroleum distillation. This 'glue' is called bitumen and the resulting material is a bituminous macadam.
Like any other man-made structures, pavements deteriorate with time and use. The two most common forms of failure in flexible pavements are permanent deformation (which causes rutting) and fatigue (which causes "alligator" cracking). The pavement engineer must find ways to reduce these failures as much as possible.