3. Railway crossing however adequately designed are accident prone ,but
they are adopted at the places where it is not possible from engineering
and economic consideration to provide road over/under bridge.
Should be located away from railway station and marshalling yards.
if unavoidable then should be located beyond shunting limits.
4. Special
A class
B class
C class
D class
CLASS I
NH
SH
For Vehicular traffic
For cattle crossing and footpaths
CLASS II
CLASS III
CLASS IV
ODR,MDR
Un imp road
within towns
Imp roads within
towns
Roads within non
municipal towns
Roads in and
around town
where traffic is
heavy
Other surfaced
roads
Earth roads
Cart tracks
Cattle crossing
and footpaths
5. BETWEEN GATES:
CLASS I
CLASS II
CLASS III
CLASS IV
9 m or equal to
width of
carriageway
immediately
outside gate
plus 2.5 m
7.5 m or equal
to width of
carriageway
immediately
outside gate
plus 2 m
5 m or equal to
width of
carriageway
immediately
outside gate
plus 1.25 m
Minimum of 2m
Whichever
is more
6. OUTSIDE GATES
CLASS I
CLASS II
CLASS III
CLASS IV
7 m or equal to
width of existing
carriageway
5.5 m or equal
to width of
existing
carriageway
3.75 m or equal
to width of
existing
carriageway
Whichever
is more
Minimum of 2m
Note : the width immediate carriageway tapers down to existing carriageway
within distance of 30 m from gate
7. Between gates : surface shall not be of lower standard than surface outside the
railway boundary. in case of cement concrete surface black topped surface
may be provided
Outside gates: surface shall not be of lower specification than that of existing
road however in case of class I and class II roads black topped surface should
be provided for distance of at least 30 m from gates
Gates employed are:
1)Swing gates
2) Lifting gates
3)Movables barriers of approved designs
Gates should be at right angle to
centre line of road
8. Minimum distance of gates from
centre line of nearest railway track
should be 3 m on BG lines and 2.5
m on MG & NG lines.
Angle of crossing between centre line of
railway track and road- it should not be
less than 45 degrees in case of Class
I,II,III roads(lower than 45 degrees can
also be provided only after special
permission by railway board). for class IV
roads angle of crossing should be 90
degrees
9. It depends upon the design speed, coefficient of friction between tyres and
road surface and max allowable value of superelevation.As per IRC:39-1986
following values should be adopted
10. BETWEEN GATES :-level for all classes
OUTSIDE GATES:A) Class I roads-same level as between the gates upto 15 m beyond
And not steeper than 1 in 40 beyond
B)Class II roads:-same level as gate upto 8 m beyond gates and not
steeper than 1 in 30 beyond
C)Class III roads-same level as between the gates upto 8 m beyond
gates and not steeper than 1 in 20 beyond
D)Class IV roads:-not steeper than 1 in 15
12. UNGUARDED CROSSING
The distance of
second sign
from crossing
An advance
warning sign
located at 200m 50-100 30from crossing
m for
60m
plain
for hilly
and
terrain
rolling
terrain
GUARDED CROSSING
The distance of
second sign
from crossing
An advance
warning sign
located at 200m 50-100 30from crossing
m for
60m
plain
for hilly
and
terrain
rolling
terrain
13. Gates should be painted white,with a red disc not less than 60 cm in diameter
in centre.the gate posts also be painted white
14. LIGHT AS OBSERVED BY ROAD
USERS
CLASS I & II
roads
Red when either
gate is closed to
road
White when gates
are opened
CLASS III roads
Same as that of
class I and II
roads but reflector
may used as
alternate of lamps
LIGHTS AS OBSERVED BY
DRIVERS OF APPROACHING
TRAINS
Class I roads
Red when get
closed across
railway track
Other cases
nil
15. 1. Latest IRC road sign indicating whether the railway crossing is manned
or unmanned shall be installed on either end at prescribed distance as
per IRC:67-1977
2. Speed limit road signs should be installed on either of gates
3. Speed breakers shall not be permitted
4. Flashing signals shall be installed on both sides of crossing after
assessing their requirements
Flashing
signals
16.
17. A kilometer stone is one of a series
of numbered markers placed along
a road or boundary at intervals of one km or
occasionally, parts of a km. They are typically
located at the side of the road or in a median
Kilometer stones are constructed to
provide reference points along the road. This can
be used to reassure travellers that the proper path
is being followed, and to indicate
either distance travelled or the remaining distance
to a destination
18. FOR NH,SH,& MDR:- The stones are of two sizes
1. Ordinary kilometer stone(small size)
2. Fifth kilometer stone(bigger size)
ORDINARY KILOMETER STONES
SIDE ELEVATION
FRONT ELEVATION
EXAMPLE
20. FOR O.D.R &V.R:-
Plate 3
In I
I
LOCALLY AVAILABLE MATERIAL SUCH AS HARD STONE , CEMENT
CONCRETE ETC
21. Ordinary km stone shall be inscribed in hindi or in local language & indicate
name & distance to the next imp town or terminal station
Fifth km stone can be inscribed only in roman and show the distance of
terminal as well as intermediate station
The place name shall be inscribed in different script in following sequence
22. On each kilometer stone its number shall be
inscribed on side of stone facing the carriage
way.This numbering is meant for maintenance
staff and will start with zero at starting station
Letters and numerals shall be of following
size
23. Chart provided in IRC:8-1980 give dimensions of the letters and numerals
24. Spacing between the standard letters or numerals are also provided in
IRC:8-1980 as follows
25. Edge clearance should be given as
Background colour should be white with
black letter and numerals
Semicircular portion should be painted
canary yellow (I.S.Shade 309) on NH,brilliant
green on SH and white on MDR
Route numbers written should be of black
colour on canary yellow and white on green
background
26. Normally kilometer stone are placed on left
hand side of road
On divided roads having central median
they should be provided on both sides of road
Kilometer stone shall be fixed at right angle
to centre line of carriageway
On embankment they shall be located on
edge of roadway beyond shoulder
27.
28. MATERIAL-locally available materials such as hard stone ,well dressed or of
reinforced cement concrete
LOCATION & SPACING- they should be fixed on either side of road land
opposite every 200 meter stone. In addition they shall be fixed at angular points
of boundary & also in places where land is likely to be encroached upon
INSCRIPTION:- The letters R,B indicating road boundary should be inscribed in
each stone & below it name of authority in which road land vests i.e P.W.D,D.B
etc
31. MATERIAL-locally available materials such as hard stone ,well dressed or of
reinforced cement concrete
LOCATION & FIXING:- They are to be located on the same side of road as one
having kilometre stone .they may be fixed in position with rammed spails in
mooram,lime surkhi concrete of lean cement concrete all around.they should be
placed at edge of formation with their side bearing the inscription facing and
parallel to centre line of road
INSCRIPTION:-the inscription carried by the stones shall be the numerals 2,4,6
and 8 marked in an ascending order in direction of increasing kilometerage
away from starting station.the numerals shall be 80 mm high. They should be
properly painted or preferably engraved
COLOUR:- the colour of shall be black on white background
32.
33.
34.
35.
36. SHAPES OF LETTERS/NUMERALS-All charecters
having an arc at top or bottom are specified as per IRC:301968
SPACING BETWEEN ADJACENT LETTERS/NUMERALS:The space between any combination of letters/numerals
may be obtained by the two step process describe in
footnote of table. this space is distance measured
horizontally between extreme right edge of preceding letter
and extreme left edge of following letter. no part of any
letter/numeral may extend into this space.
37.
38.
39.
40.
41. The mountainous and steep terrains are collectively
known as hilly terrains
TERRAIN
CROSS SLOPE`
MOUNTAINOUS
25%-60%
STEEP
>60%
Hill roads are classified in five
catagories.
HILL ROADS
NH
SH
MDR
ODR
VR
42. First step for alignment determination is fixation of obligatory
points and control points which are determine by following factors
•Administrative needs
•Development needs
•Strategic needs
To determine a few alternative alignment the investigation should
start from obligatory summit points and proceed downwards
Optimum alignment is the one which yeilds least overall
transportation cost taking into account cost of construction and
maintenance cost of road and have least adverse affect over
environment
Route should avoid introduction of hair-pin bends as far as
possible
43. If provision of such bends are unavoidable then
number of hair pin bends should kept at absolute
minimum and inevitability of each bend should
be recorded in reconnaissance report
the bends should be located on flat and stable
hill slopes and they should be avoided in valleys
Series of hair pin bends on same face of hill
should be avoided
HAIR-PIN BENDS
44. 1)Reconnaissance
2)Preliminary survey
3)Determination of final centre line
4)Final location survey
1)RECONNAISSANCE
It is primary step of fixing the alignment, during this a
general route for alignment is selected. A trace is cut
thereafter corresponding to this an access is provided
to subsequent surveys
It can be conducted in following steps
STUDY OF SURVEY SHEETS & MAPS:-in India
topographical sheets are available to the scale of
1:50000,after study of the maps,a number of
alignments feasible in a general way are selected.
Topographical sheet
45. AERIAL RECONNAISANCE:- it provide a bird
eye view and help to identify the factors which
call for rejection or modification of any of
alignment.
GROUND RECONNAISANCE:- It consist of
the general examination ground by walking or
riding along the probable routes. it will be
advantageous to start reconnaissance from
highest obligatory point.
FINAL RECONNAISANCE OF INACCISABLE
AND DIFICULT STRETCHES:Above stretches may disclose certain stretches
which call for detail examination. A trace cut is
specially made in such section for inspection, it
is also desirable to have one last round of
aerial reconnaissance to resolve remaining
doubts
46. 2)PRELIMINARY SURVEY:PEGGING AND TRACE CUT:- The line and grade of selected
alternative is pegged and the trace is cut along the pegged route
•The gradient to be followed at this stage should be easier than those
proposed to be achieved for the road by the margin of 10 to 20%
•The indication about the grade should be provided at conspicuous
locations so that they can be easily visible from distance
•Trace cut consist of 1.0 to 1.2 m wide track constructed along the
selected alignment to facilitate access to the area for inspection and
survey
•It is desirable that a senior engineer should walk over the trace cut
before further survey work is undertaken to derive benefit from its
experience for selection of best possible route
47. SURVEY PROCEDURE
•The survey should cover a strip width of 30m in straight/slightly curved and
60 m at sharp curve and hair pin bends
•Traverse along the trace should be run with a theodolite and all angles
measured by double reversible method, distance should be measure with
metallic tape and chain
•The transit station should be marked by means of stakes and numbered in
sequence
•Leveling work include taking ground along the
trace cut at intervals of 10 m and at abrupt
changes in slope and also establishing bench
marks at intervals of 250 m
•At sharp curves and difficult location detailed
leveling may be done for plotting of contours.
Interval of contours may be taken 2m though
this could be varied as per site conditions
48. MAP PREPARATION:Plan should be prepared to determine final centre line of road . at
critical section plan should show contour at interval of 1-3 m. scale
of may be adopted as horizontal scale of 1:1000 and vertical scale
of 1:100.scale can be increased at difficult location such as hair pin
bends
DETERMINATION OF FINAL CENTRE LINE:•Best alignment should be selected and study of horizontal
alignment in conjunction with profile is carried out and proper
adjustments should be made
•Horizontal curve including spiral transition should be designed
and final central line should be marked over the map
•Vertical curve should be designed and profile shown in
longitudinal section
49. 3)FINAL LOCATION SURVEY:TRANSIT SURVEY:i.
All angles should be measured with a transit, reference marks
should be fixed for this purpose
ii. These marks should be placed at 20 m at straight reaches and 10 m
at curves
iii. Reference pillars/Burjis should fixed on ground and should not be
disturbed during construction . the maximum spacing between them
should not be greater than 100m
iv. Distance should be measured with help of theodolite
v. Final centre line should be properly staked ,stakes being fixed at 20
m interval
50. BENCHMARKS:T o establish firm vertical control for location, design and construction
benchmarks established during preliminary survey should be re
checked and where likely to be disturbed during construction reestablished at interval of 250 m and or near all drainage crossing
51. The design speed of various categories of hill road
are:-
Normally ruling design speed should be the guiding criterion for
correlating various geometric features. Minimum design speed may
however be adopted in sections where site conditions including cost
do not permit that
52. A hairpin turn (also hairpin bend, hairpin corner,
etc.), named for its resemblance to a hairpin/bobby
pin, is a bend in a road with a very acute inner
angle, making it necessary for an oncoming vehicle
to turn almost 180° to continue on the road.
Hairpin turns are often built when a route climbs up
or down a steep slope, so that it can travel mostly
across the slope with only moderate
steepness, and are often arrayed in a zigzag
pattern. Highways with repeating hairpin turns allow
easier, safer ascents and descents of
mountainous terrain than a direct, steep climb and
descent, at the price of greater distances of travel
and usually lower speed limits, due to the
sharpness of the turn. Highways of this style are
also generally less costly to build and maintain than
highways with tunnels.
53.
54. Inner and outer edges of roadway should be concentric with respect to
centre line of pavement
Where hair pin bends have to be introduced a minimum intervening
length of 60 m should be provided between successive bends to enable
driver to negotiate the alignment smoothly
At hair pin bends preferably the full
roadway width should be surfaced
55. Passing places or lay-byes are require to cater following requirements
1)To facilitates crossing of vehicles from the opposite direction
2)To tow aside a disabled vehicle so that it does not obstruct traffic
TYPE OF ROAD
NH,SH having roadway width as per
IRC:52-1981
PROVISIONS FOR LAY-BYES
NO NEED
Single lane sections of NH/SH having
narrow roadway width
May be provided with respect to
actual needs
Other roads
Provided at rate of 2-3per kilometer
Lay-byes should be 3.75m wide,30m long on inner edge(towards the
carriageway)and 20 m long on the farther side
56. Minimum lateral clearance(distance between the extreme edge
of carriageway and the face of nearest support whether a solid
abutment, pier or column) should equal to normal shoulder width.
On lower category roads in hill areas having comparative
narrow shoulders, it will desirable to increase width at underpass
to a certain extent keeping in mind the principles of IRC:54-1974
57. Minimum vertical clearance of 5m should be
ensured over the full width of the roadway at all
underpasses and similarly at overhanging cliffs
and any semi-tunnel sections etc
The vertical clearance should be measured
with regard to the highest point of
carriageway(the crown or the super elevated
edge of the carriageway)
Allowance for any future raising/strengthening
of pavement is also be made)
58.
59. •BRIDGE:-It is a structure having total length of above
6m between inner face of dirt wall for carrying traffic or
other moving loads over the obstruction such as
Channel, roads or railways
It is of two types
1)MINOR BRIDGE:-total length up to 60 m
2)MAJOR BRIDGE:-Total length greater than 60 m
•CULVERT:-It is a cross drainage structure having a
total length of 6 m or less
•HIGH LEVEL BRIDGE:-bridge which carries the
roadway above high flood level
•SUBMERSIBLE BRIDGE /VENTED CAUSEWAY:-bridge designed to be
overtopped during floods
60. •LINEAR WATERWAY:- it is width of the waterway between the extreme
edges of water surface at highest flood level measured at right angle to the
abutment faces
•EFFECTIVE LINEAR WATERWAY:-it is the total width of waterway of the
bridge at HFL minus the effective width of obstructions
61. •SAFETY KERB:- it is a roadway kerb for occasional use of pedestrian traffic
SAFETY KERB
•WIDTH OF CARRIAGEWAY:- it is minimum clear width measured at right
angle to longitudinal centre line of the bridge between inside face of roadway
kerb
•WIDTH OF THE SAFETY KERB:-It is minimum clear width any where within
the height of 2.25 metres above the surface of the footway kerb
62.
63. •In case of road kerbs section shown below should be adopted. for bridges
across deep gorges, major rivers, open sea the design below can be modified
suitably
•They should be so designed that they would be safe for vertical and
horizontal loads
•A safety kerb will have same outline as that of roadway kerb except top width
shall not be less than 750mm
64. HIGH LEVEL BRIDGE
FOR ROAD TRAFFIC
WIDTH
SINGLE LANE
4.25 M
TWO LANE
7.5 M
For every additional
lane 3.5 m width
should be increased,
bridge should be
provided only single
lane or multiple of 2
lane
•If median is provided than its width shall not be less than 1.2 m
•Minimum width of footpath should be 1.5 m
65. •Apart from these following conditions must be satisfied by 2 lane bridge
66. •Super elevation on the deck on horizontal curve should be provided as
per relevant IRC standards
•Due allowance should be made for the effect of superelevation on the
stresses in various members of the bridge
•If there is a change of gradient on the bridge deck suitable vertical shall
be introduced conforming the stipulations in IRC:SP-23
67. •The approaches on either side of straight bridge shall have minimum
length of 15 m and suitably increased where necessary to provide
minimum sight distance
•If there is a change of gradient, suitable vertical curves shall be
introduce as per IRC:23
•A single vertical curve shall be provided for bridges having a total
length of 30 m
•Approaches to vented causeway likely to be affected by flood shall be
provided with suitable designed safety works
68. •Suitably designed crash barriers should be provided as safeguard
against errant vehicles
•
•They should be of metal or rcc and their design should consider
following factors
•1)impact of vehicle colliding the vehicle
•2)safety of occupants of vehicle colliding the barrier
•3)safety of other vehicle near the collision site
•4)safety of vehicle and pedestrian underneath the bridge
•5)aesthetics and freedom of view of passing vehicles
•They shall provide smooth and continuous face on traffic side
•Suitable reflective devices shall be provided on the traffic face of
barrier at intervals to ensure visibility
69. Types of crash barriers are:1)Vehicle crash barriers:-provided for bridges without
footpaths
2)Combination railing/vehicle pedestrian crash
barrier:-provide for bridges with footpaths
3)High containment barriers:-provided mainly on
bridges over busy railway lines complex interchanges
and other similar high risk location.
70.
71.
72. •High level bridges may preferably built in longitudinal gradient with
suitably designed cross drains
•Suitable vertical recess in the piers may be provided to
accommodate the drainage pipes rather than providing drip courses
underneath deck slab
•All carriageway and footpath surfaces have anti skid characteristics
73. •All multi lane shall be provided with overhead signs and signals as per
IRC:67
•Non luminous signs shall not be permitted
•Arrangement of supports for overhead structures are shown as below
74. Minimum horizontal & vertical clearance for single & multiple lane
bridges with vehicular traffic are shown in figure
Unless otherwise specified bridges shall have all their parts constructed
to secure the minimum clearance for traffic given in figure
75. •For footways and cycle tracks a minimum vertical clearance of 2.25 m
shall be provided
•For a bridge constructed on a horizontal curve with super elevated road
surface, the horizontal clearance shall be increased on side of inner
curve by a amount of 5 m multiplied by super elevation
76. • Lighting masts may be of the conventional type of suitable heights not
less than 5.5m
•The lamp may be chosen from the following
1.
2.
3.
4.
5.
6.
incandescent lamp
Mercury vapour lamp
High pressure mercury lamp with clear fluorescent bulbs
Tubular fluorescent bulb
Sodium vapour lamp
Mercury halide lamp
• The height & spacing should be such that to achieve minimum level
of illumination of 30 lux
•Illumination level for the vehicular and pedestrian subways may be kept
same as those on approaches at either end of subways.
