Camber/ Cross Fall
The reason for that is because most roads have a camber to them that helps water drain off of them rather than pooling up in the center of the road.
The camber is any curve on a surface, and in this case refers to upward curve from the edge of a road towards the center.
As per IRC SP:73:2015 Clause; 2.8.1 - The crossfall on straight sections of road carriageway, paved shoulders and paved
portion of median shall be 2.5 percent for bituminous surface and 2.0 percent for cement
concrete surface.
As per IRC SP:73:2015 Clause; 2.8.2 - The cross fall for earthen shoulders on straight portions shall be at least 0.5 percent steeper than the slope of the pavement and paved shoulder subject to a minimum of 3.0 percent. On super elevated sections, the earthen portion of the shoulder on the outer side of the curve shall be provided with reverse crossfall of 0.5 percent so that the earth does not drain on the carriageway and the storm water drains out with minimum travel path.
As per IRC SP:73:2015 Clause; 2.8.3 -The two-lane roads shall be provided with a crown in the middle. On horizontal curves, the carriageway shall be super elevated.
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Geometric Design and Alignment
As per IRC SP:73:2015 Clause; 2.9.1 -Geometric design shall conform to IRC:73 except as otherwise indicated in this Manual. While designing the horizontal alignment, the following general principles shall be kept in view:
i) Alignment should be fluent and it should blend well with the surrounding topography.
ii) On new roads, the curves should be designed to have largest practical radius,
but in no case less than ruling value corresponding to ruling design speed.
iii) As a normal rule, sharp curves should not be introduced at the end of long tangent since these can be extremely hazardous.
iv) The curves should be sufficiently long and they should have suitable transitions to provide pleasing appearance.
v) Reverse curves shall be avoided as far as possible. Where unavoidable,sufficient length between two curves shall be provided for introduction of requisite transition curves.
vi) Curves in the same direction, separated by short tangents known as broken back curves, should be avoided as far as possible.
vii) To avoid distortion in appearance, the horizontal alignment should be coordinated carefully with the longitudinal profile.
viii) Hair pin bends on hilly terrain should be avoided as far as possible.
The reason for that is because most roads have a camber to them that helps water drain off of them rather than pooling up in the center of the road.
The camber is any curve on a surface, and in this case refers to upward curve from the edge of a road towards the center.
portion of median shall be 2.5 percent for bituminous surface and 2.0 percent for cement
concrete surface.
As per IRC SP:73:2015 Clause; 2.8.3 -The two-lane roads shall be provided with a crown in the middle. On horizontal curves, the carriageway shall be super elevated.
Image Source:engineeringdiscoveries
Geometric Design and Alignment
As per IRC SP:73:2015 Clause; 2.9.1 -Geometric design shall conform to IRC:73 except as otherwise indicated in this Manual. While designing the horizontal alignment, the following general principles shall be kept in view:
i) Alignment should be fluent and it should blend well with the surrounding topography.
ii) On new roads, the curves should be designed to have largest practical radius,
but in no case less than ruling value corresponding to ruling design speed.
iii) As a normal rule, sharp curves should not be introduced at the end of long tangent since these can be extremely hazardous.
iv) The curves should be sufficiently long and they should have suitable transitions to provide pleasing appearance.
v) Reverse curves shall be avoided as far as possible. Where unavoidable,sufficient length between two curves shall be provided for introduction of requisite transition curves.
vi) Curves in the same direction, separated by short tangents known as broken back curves, should be avoided as far as possible.
vii) To avoid distortion in appearance, the horizontal alignment should be coordinated carefully with the longitudinal profile.
viii) Hair pin bends on hilly terrain should be avoided as far as possible.
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