Types & Classification: Roads | Transportation Engineering - Civil Engineering (CE) PDF Download

History: 
The invention of wheel brought up the necessity of providing a hard surface to move the vehicles. Such trace of road network is believed to have existed in Mesopotamia in the period of 3500 BC. The first road on which there is some authentic records is that of Assyrian empire constructed by about 1900 BC. Only during Roman empire the roads were built in large scales.

Roman Roads: Many of the early roman roads were of elaborate construction.

 

The main features of Roman roads are:

□     They were built straight regardless of gradients
□     They were built after the soft soil was removed and a hard stratum was reached
□     The total thickness of the construction was as high as 0.75 to 1.2 mtrs at some places, even though the magnitude of wheel loads of animal drawn vehicles was very low.
□     Larges stones were laid in lime mortar at the bottom. Vertical kerbs stones were place along the side of trench.
□     Large size of broken stones missed in lime mortar was laid over the large stones


FRENCH Roads (Tresaguet Construction):
The main feature of this was that the thickness of construction need be only in the order of 30 cm. Further due consideration was given to sub grade moisture condition and drainage of surface water.



1) The sub grade was prepared by large foundation stones
2) The top wearing course was made of smaller and compacted to a thickness of about 5 stones cm at the edges and gradually increased towards the centre, giving a cross slope.
3) The shoulders were also provided cross slope to drain the surface water.

John Macadam Construction: 
□ It is the first method based on scientific thinking.
□ It was realized that the stresses due to wheel load of traffic gets decrease at the lower layers of the pavement and therefore it is not necessary to provide large and strong boulders stones as foundation.
□ Various modem roads are subsequent improvement of this type of constructions




Necessity of Highway Planning 
Planning is the basic requirement for any new project or an expansion program me.
Particularly when funds available are limited and requirement are higher.
The objects of planning are:
1.To plan a road network for efficient and safe traffic operations, but at minimum cost. Here the costs of construction, maintenance and renewal of pavement layers and the vehicle operation costs are to be given due consideration.
2.To arrive at the road system and the lengths of different categories of roads this could provide maximum utility and could be constructed with in available resources during the plan period.
3. To fix up date wise priorities for development of each link based on utility as the main criterion for phasing the road development programme.
4. To plan for future requirement and improvements of roads in view of anticipated developments.
5.To work out financing system.

Classification of Roads 
Types of Roads
i) Based on Seasons of the year
a. All weather roads: are those which are negotiable during all weather, expect at major river crossing where interruption to traffic is permissible up to a certain extent.
b. Fair weather roads: are those, the traffic may be interrupted during monsoon season at causeways where streams may overflow across the road.

ii) Based on type of carriage way
a. Paved Roads: provided with a hard pavement course at least of WBM layer
b. Unpaved Roads: not provided with hard pavement surface. Earth and gravel roads are unpaved roads.

iii) Based on type of pavement surface
a. Surface Roads: provided with a bituminous or cement concrete surfacing.
b. Un Surfaced Roads: not provided with bitumen or cement concrete surfacing.

iv) Based on traffic volume
a. Light: Roads on which traffic volume are low. Examples village are ODR roads.
b. Medium: Roads on which the traffic intensity is relatively more to ODR.
c. Heavy: Roads on which the traffic intensity is high.( NH and SH).

v) Based on Load transported or tonnage
a. Class A or Class I: where the vehicles carries less tonnes of load on the roads.
b. Class B or Class II : Roads on which the vehicles carry more loads( LCV, Medium commercial vehicles)
c. Class C or Class III : Roads on which the trucks with heavy tonnes of load is allowed.

vi) Based on Location and function
a. National Highway :
 b. State Highway :
 c. Major district Roads :
 d. Minor or Other District Roads :
 e. Village Roads : 

vii) Based on 3rd 20 year road plan
a. Primary System: (Expressway & NH)
b. Secondary System ( SH & MDR)
c. Tertiary System or Rural Roads (ODR & VR)

viii) Classification of Urban Roads
a. Arterial Roads
b. Sub- arterial Roads
c. Collector streets
d. Local Streets