It may be defined as "Design of visible features of highway"
(geometric design of highway)
(geometric design of highway)
Syllabus to cover:
- Cross- Sectional Elements
- Sight Distance
- Horizontal Alignment
- Vertical Alignment
1) Cross- Sectional Elements:
Highway Cross-Section elements include the various parts of a road that are present to make a safe and comfortable journey of the vehicle as well as other road users. These parts include Center-line, the travel lane, shoulder, side-slopes, Median area, Pedestrian and bicycle pavements, drainage and clear zone etc. In other words, it defines the cross section of a Highway and consists of the elements that constitute the cross section part of the highway.
- Camber:
It may be defined as "Transverse slope provided to the road to drain off surface water".
- Types of Camber:
i) Straight line camber
ii) Parabolic camber
iii) Combined camber
i) Straight line Camber:
- This type of camber is provided by meeting two straight surfaces at the crown.
- Crown is the central and top most point on the surface of the road.
- The edge shape produces inconvenience to the traffic so it is not used in general.
[1/n = y/(w/2)]
ii) Parabolic Camber:
- Parabolic camber is provided by providing a parabolic shape to the surface of the road.
- It is also not used in general because it has steep slopes towards the edges, which can create the outward thrust to the vehicles.
iii) Combined Camber:
- Mixed camber is formed by use of the straight surfaces at the edges but parabolic surface at the center.
- It is mostly used for the road construction because both the problem of the earlier two are solved if we use this camber.
- Engineer Ji IP | Important Points:
i) For cement crete pavement (Rigid pavement) straight line camber is preferred.
ii) Parabolic camber is preferred by fast moving vehicle for frequent overtaking because, centered portion of parabolic camber is flat.
iii). Gradient is twice of camber approx.
- Demerits of Excessive Camber:
i) Transverse tilt of vehicle.
ii) Formation of ruts along the outer of pavement due to unequal load distribution.
iii) Center line tendency of driver.
- Width of Pavement or Carriageway:
i) Single Lane Road: 3.75m
ii) Two Lane Road without Kerb: 7.00m
iii) Two Lane Road with Kerb: 7.5m
iv) Intermediate Lane: 5.5m
v) Mullti Lane Road: 3.5m/lane
- Shoulder:
i) Extra width provided adjacent to the road to use as emergency lane is shoulder.
ii) Shoulder is more rougher than road, so that it cannot be used as a regular traffic lane.
iii) Color of shoulder is different from road.
iv) It should be use only in emergency.
v) According to IRC (Indian Road Congress) minimum width of shoulder for 2-lane rural highway is 2.5m.
vi) Shoulder & Kerbs demarcates the road boundary and it provided lateral support to the pavement.
- Width of Roadway:
"it is width of carriageway along with separators + shoulders"
- Width of formation for various classed of roads:
- NH/SH
- MDR
- ODR
- VR
- Kerb:
"it is the boundary between pavement and median or footpath or shoulder"
- Types of Kerb:
i) Lower mountable Kerb
ii) Semi-barrier kerb
iii) Barrier kerb
iv) Sub-merge kerb
- Right of Way:
i) it is the width of land acquired for the road along its alignment.
ii) it should be adequate to accommodation all the cross sectional elements of the highway and may reasonably provided for future developments.
- This type of camber is provided by meeting two straight surfaces at the crown.
- Crown is the central and top most point on the surface of the road.
- The edge shape produces inconvenience to the traffic so it is not used in general.
[1/n = y/(w/2)]
ii) Parabolic Camber:
- Parabolic camber is provided by providing a parabolic shape to the surface of the road.
- It is also not used in general because it has steep slopes towards the edges, which can create the outward thrust to the vehicles.
iii) Combined Camber:
- Mixed camber is formed by use of the straight surfaces at the edges but parabolic surface at the center.
- It is mostly used for the road construction because both the problem of the earlier two are solved if we use this camber.
- Engineer Ji IP | Important Points:
i) For cement crete pavement (Rigid pavement) straight line camber is preferred.
ii) Parabolic camber is preferred by fast moving vehicle for frequent overtaking because, centered portion of parabolic camber is flat.
iii). Gradient is twice of camber approx.
- Demerits of Excessive Camber:
i) Transverse tilt of vehicle.
ii) Formation of ruts along the outer of pavement due to unequal load distribution.
iii) Center line tendency of driver.
- Width of Pavement or Carriageway:
i) Single Lane Road: 3.75m
ii) Two Lane Road without Kerb: 7.00m
iii) Two Lane Road with Kerb: 7.5m
iv) Intermediate Lane: 5.5m
v) Mullti Lane Road: 3.5m/lane
- Shoulder:
i) Extra width provided adjacent to the road to use as emergency lane is shoulder.
ii) Shoulder is more rougher than road, so that it cannot be used as a regular traffic lane.
iii) Color of shoulder is different from road.
iv) It should be use only in emergency.
v) According to IRC (Indian Road Congress) minimum width of shoulder for 2-lane rural highway is 2.5m.
vi) Shoulder & Kerbs demarcates the road boundary and it provided lateral support to the pavement.
- Width of Roadway:
"it is width of carriageway along with separators + shoulders"
- Width of formation for various classed of roads:
- NH/SH
- MDR
- ODR
- VR
- Kerb:
"it is the boundary between pavement and median or footpath or shoulder"
- Types of Kerb:
i) Lower mountable Kerb
ii) Semi-barrier kerb
iii) Barrier kerb
iv) Sub-merge kerb
- Right of Way:
i) it is the width of land acquired for the road along its alignment.
ii) it should be adequate to accommodation all the cross sectional elements of the highway and may reasonably provided for future developments.
- Types of Kerb:
i) Lower mountable Kerb
ii) Semi-barrier kerb
iii) Barrier kerb
iv) Sub-merge kerb
- Right of Way:
i) it is the width of land acquired for the road along its alignment.
ii) it should be adequate to accommodation all the cross sectional elements of the highway and may reasonably provided for future developments.
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