This diorama is based upon a section of the A2 dual carriageway in Eltham in south-east London. The road in sunk within a concrete trench as an underpass. 
The model makes an ideal background upon which any 1/76 scale vehicle can be displayed and / or photographed. A range of scenes can be enacted - heavy traffic, roadside breakdown, incidents etc.
A detailed road surface with hard shoulders and median strip is supplied along with the concrete side walls. The road markings do not specify direction, so a 'left hand' or 'right hand' drive scene can be shown.
The dual carriageway with hard shoulders is 13" wide. Each section of road as 11" long. See the illustrations for the relative sizing of the models produced from the 'small' and 'large' packs.
Of course, several packs can be used together.   
Note that this is not a complete road system -  for there are no curves or exits. However, it might be usefully used as an underpass installed as a scenic item on a model railway.