It explains about the highway alignments and cross-sectional elements of a road as per IRC. Also noted some important numerical values regarding the sectioning elements.

1. Welcome to Civil Genics...

2. Highway Alignments
• alignment - centre line layout of highway
Factors controlling alignments;
i. Obligatory points
ii. Traffic generation
iii. Geometric design
iv. Economics
v. other considerations

3. Obligatory points
• control the alignment
• 2 types; points through which - necessarily pass through
and, should not pass through
• points - should pass through - hillpass, bridge site, intermediate towns etc.
• A hill pass - crossing by - a tunnel, go around the hill, deviate to get a alignment
• A road bridge - to be located at river has less wider, straight, approaches should
not be curved
• towns - attract and generate traffic
• points - should not pass through - conservation elements (lakes, parks etc.), built
up areas, water logged areas etc.

4. Cross sectional elements
• Factors affecting geometric design - cross sectional elements

5. 1) Right of way
 “permanent land width” over which authority has a right.
 width = (carriageway + shoulders + road margins)
2) Carriageway
 meant for vehicular traffic moves.
 width of CW - single lane without kerb - 3.5m
single lane with kerb - 3.75m
double lane - 7m
double lane with kerb - 7.5m
intermediate CW - 5.5m
(standard width considering for vehicle - 2.44m)
 multi lanes can be provided as 3.5m per lanes.

6. 3) Medians
 separates opposing stream of traffic on CW (urban roads)
 minimum width of CW - 7.5m on each side
 minimum width of medians - 1.2m
 should be of uniform width.
4) Kerbs
 curved and raised stones - barriers between shoulders & CW
 types; low or, mountable - 10cm height
semi-barrier - 15cm height
barrier - 20cm height
Submerged type

7. 5) Camber
 cross slope provided in tanseverse direction of highway.
 to drain away water, to prevent water entering subgrade, to provide skid
resisitance.
 Rates of camber; (Heavy to light)
cement concrete & high bituminous - 1 in 50 (2%) - 1 in 60(1.7%)
thin bituminous surface - 1 in 40 (2.5%) - 1 in 50 (2%)
WBM & gravel pavement - 1 in 33 (3%) - 1 in 40 (2.5%)
earth - 1 in 25 (4%) - 1 in 33 (3%)
 Shapes; - parabolic
- straight line
- combination of both

8. 6) Shoulders
 as emergency lanes - rough surface than CW.
 minimum shoulder width - 2.5m
7) Road Margins
 footpath, service roads, bus bays etc.
IRC recommended gradients for different terrains
3.3%

9. Thank you..