Intersection,types
Download as PPTX, PDF37 likes20,769 views
This document discusses different types of road intersections. It describes grade separated intersections that allow vehicles to cross at different levels, such as overpasses and underpasses. It also discusses at-grade intersections, including various interchange designs like cloverleaf, diamond, and directional, that eliminate conflicts between crossing traffic streams. Roundabouts are also covered as a type of at-grade intersection where vehicles circulate around a central island in one direction. Design elements like radius, width, and sight distance important for intersections are highlighted.
Intersection,types
- 2. Road Intersection • An intersection is the area shared by the joining or crossing of two or more roads. • It is also a point of large number of major conflicts, besides a point of decision. • These conflicts may be due to the crossing maneuvers of vehicles moving in different directions. • They are mainly of 2 types 1. Grade separated intersection 2. At grade intersection INTERSECTION
- 3. Grade Separated Intersection • This are the intersections at which the vehicles crosses at different levels. • They cause less hazard and delay than grade intersections. • The objective of this is to eliminate all grade crossing conflicts and to accommodate other intersecting maneuvers by merging, diverging and weaving at low relative speed. • It increases the capacity of roads and reduce the congestions. INTERSECTION
- 4. 1. Underpass • It is an underground passageway, completely enclosed except at the openings,commonly at each end. • A tunnel may be for foot or vehicular road traffic, for rail traffic. • If an underpass is constructed for pedestrians and/or cyclists beneath a road or railway, allowing them to reach the other side in safety, then such a construction is termed as a Subway. INTERSECTION
- 5. INTERSECTION
- 6. 2. Overpass • It is also known as a flyover, is a bridge, road, railway or similar structure that crosses over another road or railway. • A pedestrian overpass allows pedestrians safe crossing over busy roads without impacting traffic. • And Railway overpasses are used to replace at- grade crossing as a safer alternative. • Overpasses allows for unobstructed rail traffic flow from mixing with vehicular and pedestrian traffic. INTERSECTION
- 7. INTERSECTION
- 8. 3. Trumpet Interchange • It is used where one highway terminates at another highway. • They are trumpet shaped intersection. • These involve at least one loop ramp connecting traffic either entering or leaving the terminating expressway with the far lanes of the continuous highway. • Trumpets are suitable at the locations where the side road exists on only one side of the freeway, and traffic is relatively low. • The principal advantages are low construction cost and are useful for highways as well as toll roads. INTERSECTION
- 9. INTERSECTION
- 10. 4. Diamond Interchange • It is the simplest form of grade separated intersection between two roadways. • The conflicts between through and crossing traffic are eliminated by a bridge structure. • The left turn crossing movement conflicts are considerably reduced by eliminating the conflict with the traffic in opposite direction. • it is suitable for locations where the volume of left turn traffic is relatively low. • It requires a minimum amount of land and is economical to construct. • The single point of exit from the major roadway eases the problem of signing. INTERSECTION
- 11. INTERSECTION
- 12. 5. Cloverleaf Interchange • A cloverleaf interchange is a two-level interchange in which left turns are handled by ramp roads . • To go left vehicles first continue as one road passes over or under the other, then exit right onto a one-way three-fourths loop ramp (270°) and merge onto the intersecting road. • The objective of a cloverleaf is to allow two highways to cross without the need for any traffic to be stopped by red lights, even for left and right turns. • The limiting factor in the capacity of a cloverleaf interchange is traffic weaving. INTERSECTION
- 13. INTERSECTION
- 14. 6. Partial Cloverleaf Interchange • It is a modification that combines some elements of a diamond interchange with one or more loops of a cloverleaf to eliminate only the more critical turning conflicts. • This is the most popular freeway -to- arterial interchange. • It is usually employed when crossing roads on the secondary road will not produce objectionable amounts of hazard and delay. • It provides more acceleration and deceleration space on the freeway. INTERSECTION
- 15. INTERSECTION
- 16. 7. Directional Interchange • A Directional interchange provides direct paths for left turns. • These interchanges contain ramps for one or more direct or semi direct left turning movements. • They are the basic patterns that use the least space, have the fewest or least complex structures, minimize internal weaving and appropriate for the common terrain and traffic conditions. limitations • high cost of construction • It requires large amount of land compared to the others. INTERSECTION
- 17. INTERSECTION
- 18. GRADE INTERSECTION • An intersection is an at-grade junction where two or more roads or streets meet or cross at same level. • They are classified as 1. Un channelized intersection 2. Channelized intersection 3. Rotary intersection INTERSECTION
- 19. 1. Channelized intersection • Vehicles approaching an intersection are directed to definite paths by islands, marking etc. and this method of control is called channelization. • It provides more safety and efficiency. • It reduces the number of possible conflicts by reducing the area of conflicts available in the carriageway. • The presence of traffic islands, markings etc. forces the driver to reduce the speed and becomes more cautious while maneuvering the intersection. • It also serves as a refuge for pedestrians and makes pedestrian crossing safer. INTERSECTION
- 20. INTERSECTION
- 21. 2. Unchannelized intersection • Thye are the lowest class of intersection, easiest in the design but most complex in traffic operations resulting in maximum conflict area and more number of accidents, unless controlled by traffic signals or police. • When no additional pavement width for turning movements is provided, it is called plain intersection. • But when the pavement is widened at the intersection area, by a traffic lane or more, it is known as flared intersection. INTERSECTION
- 22. INTERSECTION
- 23. 3. Rotary Intersection • The rotary intersection of roads is also called as traffic rotary which is nothing but enlarged intersection of roads where vehicles cross roads or change their direction without stopping. • All vehicles coming from different roads move in single direction around the central island and diverges into required exit. INTERSECTION
- 24. INTERSECTION
- 25. Design elements 1. Design Speed • It should be passed with low speed which will results the safety without any collision. • Speed restriction board should be provided on the road towards rotary intersection. 2. Shape of Central Island • The shape of Central Island should not contain any corners. • It should be formed by curves to allow the comfortable rotations around it. • The shape is dependent upon number of roads meeting at that junction. • The shapes generally provided are circular, elliptical, turbine and tangential. INTERSECTION
- 26. 3. Radius of Rotary Roadway • The radius of roadway is dependent upon the shape of Central Island and the frictional force. • If it is circular shape, radii are similar at all points and if it is elliptical or tangent radii is different at different points. 4. Weaving Angle and Weaving Distance • The weaving angle should be small but minimum of 15ois maintained. • The weave length should be at least four times the width of weaving section. INTERSECTION
- 27. 5. Width of Carriageway at Entry and Exit • The width of carriage way at entry and exits is dependent of volume of traffic in that particular region or area. • minimum width of 5.0 meters should be maintained for rotary intersections. 6. Width of Rotary Roadway • The width should be equal to the effective width of weaving section. INTERSECTION
- 28. 7. Curves at Entrance and Exit • Entry curve radius can be provided as same as radius of central island. • the vehicle accelerates at exits hence the radius of curve at exit should be greater than the radius of curve at entrance. 8. Sight Distance • The sight distance provided at rotary intersections should be as higher as possible and value must be less than the stopping sight distance. INTERSECTION
- 29. 8. Camber and Super Elevation • if the vehicle is changing its direction to its opposite side ,the vehicle may over turn or slip, to overcome this, minimum cross slope is provided which is nothing but camber. • This camber acts as super elevation in case of rotary roadways. INTERSECTION
- 30. Thank you INTERSECTION For more…. Mail to aglaiaconnect2018@gmail.com