This I have taken from my seminar topic during my B.E. final year.
1. Shoulders are essential for safety as well as for development of the full traffic capacity of the highway.
2. It has been observed that increased shoulder width has a marked effect on accident rate reduction, but excessive width led to increased road accidents. Although many other factors such as traffic volume, environmental conditions and speed plays significant role in accident trends.
3. Shoulders allow both passing and overtaking of vehicles safely and conveniently. Which are most difficult on single lane road on high traffic.
Shoulders are defined as "the portion of the roadway continuous with the traveled way for accommodation of stopped vehicles, for emergency use, and for lateral support to base and surface courses.
i. Rolled earth shoulders
ii. Gravel shoulders
iii. Stabilized shoulders
iv. Grass shoulders
v. Brick paved shoulders
vi. Cement concrete shoulders
1. The shoulders are constructed in thin layers of 10 cms in thickness, and should be rolled with a suitable power or hand roller at the proper moisture content to ensure maximum stability.
2. Rolling of earth shoulders should start at the outer edge with the rolling process carried out towards the pavement, each pass overlapping the previous one.
1. Gravel shoulders are most suitable in the semi-arid-zone or in the desert area.
2. The gravel is spread in 10 cm thick layers on the compacted sub grade.
3. In spreading the gravel, great care is taken to seed that it is not dumped; otherwise there is a danger of segregation of the sizes.
The composition for the stabilized shoulder may consist of soil-gravel, crushed stone, soil-sand, soil-cement, soil lime, sand bitumen and bituminous surface treatment or any number of locally available materials.
1. Grass shoulders are feasible in regions not affected by frost or subjected to prolonged rains, until a moderately heavy volume of traffic is reached.
2. They are inadequate where the pavement is narrow, i.e.; single-lane road and the traffic is heavy
The construction of the brick paved shoulder is quite common, as the brick pavement has proved to be most effective in increasing the width of the pavement and in providing the lateral support to the pavement.
Precast concrete slabs with a nominal reinforcement may be used as shoulders in combination with stabilized or other types of shoulders
1. WIDTH
2. STABILITY
3. TEXTURE
4. CROSS SLOPE
5. FUNCTIONS
As per IRC:73:1970
Shoulder width = Yz [Roadway width - carriageway width]
1. Shoulders are made sufficiently stable to support occasional vehicle loads in all kinds of weather without rutting.
2. A suitable stabilized shoulder can be obtained by use of knowledge and practices that are applied in the design of highway surfaces.
1. The selection of surface treatment for shoulders is guided not only by traffic volume but also by the colour and texture contrast desired between the shoulder and the adjacent pavement.
2. The through traffic lanes are made clearly visible at all times, particularly at night or in poor weather conditions.
3. Shoulder contrast enhances the beauty of the road.
1. The provision of adequate cross slope for all types of shoulders is very essential for an efficient removal of surface water from the carriageway and the shoulder it self
2. According to IRC: 73(1980) the cross slope of earth shoulder should be at least 0.5 percent steeper than the slope of the pavement subject to a minimum of 3 percent.
Highway shoulders influence greatly the safety, strength and traffic carrying capacity of adjacent traffic lanes, shoulders mainly provide two important safety and engineering functions
(1) Highway shoulders are important for single-lane or two-lane roads, because they provide accommodation for stopped vehicles, allow both crossing and overtaking of vehicles safely and conveniently. They provide lateral support to the base and surface course also.
(2) The speed of moving vehicles is not substantially affected by width of shoulder, if latter is more than 1.2 m in width.
(3) Speed of vehicle gets reduced during overtaking . The amount of reduction depends upon the condition of shoulder, type of vehicle and width of carriageway. On a 2-lane roads, speed of a car reduces by 5 per cent while crossing another car on a section where shoulder is in good condition. This reduction increases to 23 per cent when shoulder condition changes to worst.
(4) Mean free speed of the vehicle increases progressively as the condition of shoulder improves from worst to good.
(1) AASHO (1959); "A Policy on Geometric Design of Rural Highways", American Association of State Highway Officials, Washington D.C.
(2) Barbaresco, James, Bair C.,Brend, O.'(1983) " Accident Implication of Shoulder Width on Two-Lane Roadways", transport Research Board, Washington D.C., pp.90-97.
(3) Belmont, D.M. (1954); "Effect of Shoulder Width on Accidents on Two-Lane Tangents", Highway Research Board Bulletin 91, HRB Washington, D.C., pp. 29-32.
(4) Chandra, S. and Kumar, P. (1996), "Effect of Shoulder Condition on Highway Capacity", Proceedings International Seminar on Civil Engineering. Practices in the Twentyfirst Century, Roorkee, India, pp. 512-519.
(5) IRC: 73 (1970), "Geometric Design Standards for Rural Highways", Indian Code of Practice, Indian Roads Congress, New Delhi.
(6) IRC: 73 (1980); "Geometric Design Standards for Rural (Non - Urban) Highways", Indian Code of Practice, Indian Roads Congress, New Delhi.
(7) Prakash, Ved. (1970): "Highway Shoulders", Indian Roads Congress Journal, Vol. 33(3), pp. 411-446.
Introduction
1. Shoulders are essential for safety as well as for development of the full traffic capacity of the highway.
2. It has been observed that increased shoulder width has a marked effect on accident rate reduction, but excessive width led to increased road accidents. Although many other factors such as traffic volume, environmental conditions and speed plays significant role in accident trends.
3. Shoulders allow both passing and overtaking of vehicles safely and conveniently. Which are most difficult on single lane road on high traffic.
Shoulders
Shoulders are defined as "the portion of the roadway continuous with the traveled way for accommodation of stopped vehicles, for emergency use, and for lateral support to base and surface courses.
Types of Shoulders
i. Rolled earth shoulders
ii. Gravel shoulders
iii. Stabilized shoulders
iv. Grass shoulders
v. Brick paved shoulders
vi. Cement concrete shoulders
Rolled Earthen Shoulder
1. The shoulders are constructed in thin layers of 10 cms in thickness, and should be rolled with a suitable power or hand roller at the proper moisture content to ensure maximum stability.
2. Rolling of earth shoulders should start at the outer edge with the rolling process carried out towards the pavement, each pass overlapping the previous one.
Gravel Shoulder
1. Gravel shoulders are most suitable in the semi-arid-zone or in the desert area.
2. The gravel is spread in 10 cm thick layers on the compacted sub grade.
3. In spreading the gravel, great care is taken to seed that it is not dumped; otherwise there is a danger of segregation of the sizes.
Stabilized Shoulder
The composition for the stabilized shoulder may consist of soil-gravel, crushed stone, soil-sand, soil-cement, soil lime, sand bitumen and bituminous surface treatment or any number of locally available materials.
Grass Shoulder
1. Grass shoulders are feasible in regions not affected by frost or subjected to prolonged rains, until a moderately heavy volume of traffic is reached.
2. They are inadequate where the pavement is narrow, i.e.; single-lane road and the traffic is heavy
Brick Paved Shoulders
The construction of the brick paved shoulder is quite common, as the brick pavement has proved to be most effective in increasing the width of the pavement and in providing the lateral support to the pavement.
Cement Concrete Shoulder
Precast concrete slabs with a nominal reinforcement may be used as shoulders in combination with stabilized or other types of shoulders
Characteristics
1. WIDTH
2. STABILITY
3. TEXTURE
4. CROSS SLOPE
5. FUNCTIONS
Width of Shoulder
As per IRC:73:1970
Shoulder width = Yz [Roadway width - carriageway width]
Width Of Roadway For Single-lane And Two-lane Road
Width of Carriageway for Different Type of Roads
Shoulder Stability
1. Shoulders are made sufficiently stable to support occasional vehicle loads in all kinds of weather without rutting.
2. A suitable stabilized shoulder can be obtained by use of knowledge and practices that are applied in the design of highway surfaces.
Shoulder Texture
1. The selection of surface treatment for shoulders is guided not only by traffic volume but also by the colour and texture contrast desired between the shoulder and the adjacent pavement.
2. The through traffic lanes are made clearly visible at all times, particularly at night or in poor weather conditions.
3. Shoulder contrast enhances the beauty of the road.
Cross Slope Of Shoulder
1. The provision of adequate cross slope for all types of shoulders is very essential for an efficient removal of surface water from the carriageway and the shoulder it self
2. According to IRC: 73(1980) the cross slope of earth shoulder should be at least 0.5 percent steeper than the slope of the pavement subject to a minimum of 3 percent.
Camber/Cross fall Values for Different Road Surface Types
Suggested Cross-Slopes for Shoulder-Surface
Functions Of Shoulders
Highway shoulders influence greatly the safety, strength and traffic carrying capacity of adjacent traffic lanes, shoulders mainly provide two important safety and engineering functions
Conclusions
(1) Highway shoulders are important for single-lane or two-lane roads, because they provide accommodation for stopped vehicles, allow both crossing and overtaking of vehicles safely and conveniently. They provide lateral support to the base and surface course also.
(2) The speed of moving vehicles is not substantially affected by width of shoulder, if latter is more than 1.2 m in width.
(3) Speed of vehicle gets reduced during overtaking . The amount of reduction depends upon the condition of shoulder, type of vehicle and width of carriageway. On a 2-lane roads, speed of a car reduces by 5 per cent while crossing another car on a section where shoulder is in good condition. This reduction increases to 23 per cent when shoulder condition changes to worst.
(4) Mean free speed of the vehicle increases progressively as the condition of shoulder improves from worst to good.
References
(1) AASHO (1959); "A Policy on Geometric Design of Rural Highways", American Association of State Highway Officials, Washington D.C.
(2) Barbaresco, James, Bair C.,Brend, O.'(1983) " Accident Implication of Shoulder Width on Two-Lane Roadways", transport Research Board, Washington D.C., pp.90-97.
(3) Belmont, D.M. (1954); "Effect of Shoulder Width on Accidents on Two-Lane Tangents", Highway Research Board Bulletin 91, HRB Washington, D.C., pp. 29-32.
(4) Chandra, S. and Kumar, P. (1996), "Effect of Shoulder Condition on Highway Capacity", Proceedings International Seminar on Civil Engineering. Practices in the Twentyfirst Century, Roorkee, India, pp. 512-519.
(5) IRC: 73 (1970), "Geometric Design Standards for Rural Highways", Indian Code of Practice, Indian Roads Congress, New Delhi.
(6) IRC: 73 (1980); "Geometric Design Standards for Rural (Non - Urban) Highways", Indian Code of Practice, Indian Roads Congress, New Delhi.
(7) Prakash, Ved. (1970): "Highway Shoulders", Indian Roads Congress Journal, Vol. 33(3), pp. 411-446.
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