THE SAFE STOPPING SIGHT DISTANCE SHOULD INVARIABLY BE PROVIDED THROUGHOUT THE LENGTH OF ALL ROADS, DESIGNED FOR THE PARTICULAR SPEED ALLOWED ON THE ROAD

The alignment of hill roads should ensure clear visibility up to the minimum stopping sight distance all along the length. It will be impracticable normally to provide visibility corresponding to the overtaking sight distance. Vision berms should be provided on the inside of the horizontal curves up to a height of 0.6 metres. The width of these berms should equal the set-back distance minus the width of drain. While designing for the safe visibility distance, it should not be ignored that drivers visual difficulty is magnified by, hazy visibility during the monsoons. The sighting distance provided on roads should not be less than the safe Stopping distance for the particular speed allowed on the road. Where the minimum stopping distance cannot be provided, warning boards should be fixed for reducing the speed. For the purpose of measuring the stopping sight distance or visibility ahead, IRC has suggested the height of the eye level of driver as 1.2 metres and the object height as 0.15 metre above the road surface. Hence stopping distance at a summit curve is that distance measured along the road surface at which an object of height 0.15 metre can be seen by a driver whose eye is at a height of 1.2 metres above the road surface. The minimum sight distance should be based on the accepted speed of the vehicles and the breaking distance required to stop and which should also include the driver's reaction time to the danger. The safe sight distance is dependent on the breaking time of the vehicle and is generally taken as being equal to twice the distance required for a vehicle to stop. Mechanical and human factors should be taken into account-- the breaks may be defective, the driver may be drunk, and these factors will need more of stopping distance and the reaction time. Hence the safe stopping sight distance should invariably be provided throughout the length of all roads:-- Er Fateh chand Guleria, Director RTI, Welfare Association registered number HPCD, 3552 , Bilaspur HIMACHAL PRADESH Phone number, 9459334377

DESIGN CRITERIA FOR HILL ROADS (HAIR PIN BENDS) :-

HILL CURVES:-- A road going on the outer side of a hill or spur has a convex curve which is known as a salient curve or blind curve. Inside curve at the valley of a hill and which is concave curve is known as re-entrant curve or open curve. Serpentine curves , hairpin bends, and corner ends have also to be provided in hill alignments. HAIR-PIN BENDS:-- Hair pin bends are circular curves with transition curves at each end. Compound circular curves can be provided instead of hair pin bends. The following design criteria should be adopted normally for the design of hair-pin bends (a) Min:design speed --20km/hr (b) road way width at apex (1) National /State highway:--11.5 m for double-lane and 9 m for single lane. (2) District roads :-- 7.5m (3) Village roads :--6.5 m(c) Min :-radius for inner curve :-14m (d) Min:-Length of the transition 15.0 m (e) Gradient-- max :1in 40 ;min 1 in 200 . Approach gradient should not be steeper than 1in 20 for 40 metres (f) Superelevation in circular portion of the curve to be 1in 10,this can be reduced to 1in 15 for light traffic roads.. Inner and outer edges shall be concentric with respect to centre line of the pavement. Straight length between two successive hair pin bends should be 60 m  min :excluding the length of circular and transition curves. VERTICAL CURVES OR SUMMIT CURVES:-- A curve with convexity upward is called a vertical curve and the design of the vertical curve is principally governed by the sight distance required to provide adequate visibility, unless the summit is so small as not to interfere with visibility. In practical a simple parabola curve is used instead of a circular are for a vertical curve, which joins the two gradients tangentially. Vertical curves are necessary at the intersections of different grades to smoothen out the vertical profile. The minimum radius of vertical curve depends upon the design speed of the road and the required safe stopping sight distance. Minimum radii and the lengths for different speeds has been recommended by the IRC for application.

IT IS NECESSARY TO FOLLOW THE ROAD DESIGN STANDARDS AND ADOPT THE RESEARCH PARAMETERS,AS RELATED TO THE CLASSIFICATION OF ROADS .

Honourable Public Works Minister Govt of Himachal Pradesh Shimla has demanded suggestive measures from the public to improve the work and conduct of the department working for the welfare of common man demanding free and fair justice from the system of governance.As for as the suggestions required for improvement on the captioned subject matter deliberation required to be maintained by the department of Public Works is concerned it is necessary to follow the guidelines and yard sticks of the code and specifications as well as the design & Scope of the nature of duty and work for the safe design loads and concern .In the case of Hilly areas construction of road should be in cutting instead of filling for which necessary design of the curves and formation of sub grade ,sub soil drainage and moisture control is too necessary where required by the soil .The preparation of base and sub base course must be followed with proper camber and the super elevation as per design and scope of the existing crust of the soling , bearing and the pavement with bituminous surfacing as per requirement of the design & scope based on the vehicular traffic density as per the recommendations made by the various Indian Road Congress ,codes and specifications, time to time issued for the improvement of passengers car unit equivalents,as related to the road capacity and design standards of the classification of roads.The thickness of the pavement design is also depends upon the wheel load applied to the pavement,the intensity of stress reduces as the depth increases from the top of the surface, as such the thickness of pavement is increased for heavier loads and a larger total volume of traffic.Hence it is necessary to protect the safety measures by way of necessary follow up and mathematic calculations related to the thickness design of pavement and bearing capacity of the soil on which the road is to be built. It is also necessary to follow computation of traffic required for the CBR .For the design , the sub grade strength must always be assessed at the maximum moisture conditions likely to occur during the entire service life of the pavement and the CBR value determined accordingly, and the CBR values are based on the laboratory tests according to IS :2720 . Geometric road design standards should be followed as required for the acceptable compromise between the road users requirement and the construction costs which depends upon the geographical conditions of the area and for which the hilly area requires more funds as compared to the plains. As for as the road gradients are concerned the maximum longitudinal gradients are taken ,in relation to the design speed and the percentage calculation and the critical length of grade should be avoided as cause for the loaden trucks to reduce speed unduly. The department of public works too responsible to follow the IRC and IS standard of codes and specifications and do the needful accordingly in the interest of better work and durability required to improve the quality of performance related to the Road design standards which must be a research based parameter.

ROAD CAPACITY MUST HAVE DUE CONSIDERATION OF THE TRAFFIC COUNTS -EQUIVALENCY FACTOR PER DAY (BOTH DIRECTIONS)

IRC 52 -1981 and 70-1977 recommend that village roads should be built up with area nine meters wide and the MDR with road land 18 meters and built up area should be 15 meters where as in the case of other district roads the open area must be 15 meters and the built up area equal to 12 meters and in the case of NH and the SH open area of land should be 24 meters and the built up area 20 meters .The carriage way width in case of the single lane is 3.75 and the two lane 7.0 meters however in case of village roads it should not be less than 3.0 meters .The above road widths are exclusive of the parapets for which usual width of 0.6 meter is necessary to provide the parapets and the road side drain ,each for and design of shoulder is too required as per the schedule under code and specifications The road capacity for single lane,3.75 meter carriage way with earth shoulder may have 1000 and single lane with hard shoulders one meter wide equal to 2500 and two lane ,7.0 meter carriage way 10000 and 5.5 meter carriage way 5000 capacity where as the four -lane divided highway it may have 20000 to 30000 capacity which must be counted on the basis of traffic count -Equivalency factor for vehicles per day (Both directions) .Three lane roads offer only limited advantage over the two lane roads and are unsafe ,where the passing sight distance can not be provided.Four lane roads should invariably be provided with median strips.