Roads Geometric design and layout planning

Roads Geometric Design And Layout Planning-Free PDF

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GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. TABLE OF CONTENTS,INTRODUCTION 1,Reference to planning 1. Classification of the road and street system 2,Measures of effectiveness MOE 3. Traffic calming 4,BASIC DESIGN PARAMETERS 4,The design vehicle 4. The design driver 5,The road surface 5,THE ELEMENTS OF DESIGN 6. Design speed 6,Ceiling speed 6,Design hour 6,SIGHT DISTANCE 8.
Stopping sight distance SSD 8,Barrier sight distance BSD 8. Decision sight distance DSD 10,Passing sight distance PSD 10. Intersection sight distance ISD 10,HORIZONTAL ALIGNMENT 13. Tangents 14,Curvature and superelevation 14,Superelevation runoff 14. VERTICAL ALIGNMENT 15,Curvature 15,Gradients 17,Climbing lanes 18.
CROSS SECTION DESIGN 19, Roads Geometric design and layout planning Chapter 7. GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. Shoulders 21,Medians and outer separators 22,Sidewalks 22. INTERSECTIONS 24,Introduction 24,Location of intersections 25. The types of intersection control 26,The form of intersections 28. Intersection components 29,Mini roundabouts 32,BIBLIOGRAPHY 35.
Chapter 7 Roads Geometric design and layout planning. GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. LIST OF TABLES, Table 7 1 Comparison between classification systems 3. Table 7 2 Dimensions of design vehicles m after Wolhuter and Skutil 1990 4. Table 7 3 Minimum turning radii 5,Table 7 4 Brake force coefficients 6. Table 7 5 Recommended design and ceiling speed 7, Table 7 6 Stopping sight distance on level roads 8. Table 7 7 Barrier sight distance 9, Table 7 8 Decision sight distance on level roads 10. Table 7 9 Passing sight distance on level roads 10. Table 7 10 Pedestrian sight distance 13, Table 7 11 Maximum superelevation for various classes of road 14.
Table 7 12 Minimum radii for horizontal curves m 14. Table 7 13 Rates and minimum lengths of superelevation runoff 15. Table 7 14 Minimum values of K for vertical curves 16. Table 7 15 Minimum length of vertical curves 17,Table 7 16 Maximum gradients on major roads 17. Table 7 17 Traffic volume warrants for climbing lanes 19. Table 7 18 Typical width of verge elements 23,Table 7 19 LOS criteria for sidewalk width 24. Table 7 20 Taper rates 30, Table 7 21 Typical edge treatments for left turns 30. Table 7 22 Design traffic conditions 32,Table 7 23 Turning roadway widths m 33. Roads Geometric design and layout planning Chapter 7. GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. LIST OF FIGURES,Figure 7 1 Truck speed on grades 5.
Figure 7 2 Stopping sight distance on gradients 9, Figure 7 3 Minimum horizontal radius for stopping sight distance 9. Figure 7 4 Intersection sight distance for turning manoeuvre 11. Figure 7 5 Intersection sight distance for crossing manoeuvre 12. Figure 7 6 Intersection sight distance for yield condition 12. Figure 7 7 Elements of the cross section 20,Figure 7 8 Typical bus stop layouts 23. Figure 7 9 Angles of skew 27,Figure 7 10 Layout of island 32. Chapter 7 Roads Geometric design and layout planning. GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. SCOPE Road design should therefore not only accom,modate public transport but actively seek to. In this chapter the major objectives are to encourage its use Adding embayed bus stops to a. route essentially designed for passenger cars does not. stress the importance of geometric design giving constitute support for the promotion of public. expression to planning concepts transport, emphasise the revised approach to the road Obviously bus routes should be designed with the bus.
hierarchy as the design vehicle This selection of design vehicle. impacts inter alia on decisions concerning maximum. suggest the importance of satisfying the needs of gradients lane widths and provision for bus stops A. all road users both vehicular and non vehicular designated bus route should have a horizontal. and alignment planned to enhance the attractiveness of. the route to would be passengers and also be highly. provide guidelines for detailed geometric design accessible to pedestrians by ensuring that walking. that will result in a safe efficient affordable and distances to the nearest bus stop are minimised. convenient road and street system Dedicated bus lanes should be provided in areas where. the volume of bus or other high occupancy vehicles. warrants their use The dedicated bus lane implies that. INTRODUCTION the street will essentially be a shared facility serving. other modes of transport as well The high volumes of. Reference to planning bus traffic that are typically achieved when a number. of bus routes converge on the CBD or some other, The ultimate objective in the creation of an urban transport hub may suggest that dedicated bus routes. place is that it should be such that people would wish as opposed to bus lanes become a practical option. to live work and play there This can only be achieved. by the closest co operation between the planner and The distinction drawn between geometric planning and. the geometric designer because the ultimate layout of geometric design is not always clear In this document. the street system effectively defines the urban area in geometric planning is described in Chapter 5 Planning. terms of its functionality and hence its attractiveness Guidelines A brief exposition of the difference. to the inhabitants between planning and design is offered below. These two disciplines must also interact closely with Geometric planning. the other disciplines involved in the provision of. services to the inhabitants As streets also form sets of Planning addresses the broad concepts in terms of. conduits along which essential services such as water which the functions of the various links in the. supply sewerage and power are conducted they street network are defined These concepts address. should be so located that they do not unnecessarily the sum of human activity whether economic. constrain the provision of these services which can be formal or informal recreational or. social the latter including educational health care. This chapter of the guidelines cannot therefore be and worship activities In this context it is pointed. read in isolation out that movement is a derived activity or demand. Both the planner and the designer are required to Previously both planning and design tended to. adopt a more holistic approach to determination of focus on areas being dedicated to single land use. the street network than has previously been the case thus forcing a need for movement between the. They may find it useful to consider the total width of living area and any other Current planning. the cross section as being hard open space only part philosophies favour the abandonment of single use. of which is dedicated to the movement function This in favour of mixed use Mixed use suggests that. part of the cross section is roughly equivalent to the people can both live and work in one area Not. road reserve as previously understood and is still only will this have the practical effect of reducing. required to address a range of trip purposes trip the demand for movement over long distances but. components and modes of travel where movement is still necessary it will support. change of the mode of movement because over, With regard to modes of travel the design of the street short distances walking and cycling are practical. network was historically predicated almost exclusively options This will further reduce the areal extent. on the passenger car Many trip makers will however required to be dedicated to movement Conceptual. always be reliant on walking or public transport as the planning leads to the definition of corridors. only modes available to them Furthermore it is not intended to support some or other activity one of. possible to endlessly upgrade the street network in which is movement. terms of a growing population of passenger cars, Roads Geometric design and layout planning Chapter 7. GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN. Corridors in association with their intended The goals of transportation as propounded by the. functions will ultimately define the horizontal Driessen Commission are the economic safe and. alignment of the streets located in them A need convenient movement of people and goods with a. for high traffic speeds will suggest high values of minimum of side effects These goals are. horizontal radius whereas reductions in radius unchanged It must be understood that in arriving. could be applied to force speeds down to match at an acceptable street design these goals apply. activities involving a mix of vehicular and non equally to all modes of travel In this respect it will. vehicular traffic Reduction of the lengths of invariably be necessary to seek compromises. tangents between curves or intersections could between the various modes The one goal seen as. serve the same purpose being non negotiable is safety For example the. safety of pedestrians cannot be compromised in, The dominant function of the corridor defines the pursuit of convenience of vehicular travel. vertical alignment in terms of maximum and, minimum acceptable gradients vertical curvature Classification of the road and street.
and length of grade For example streets with a system. predominantly pedestrian function should ideally be. flat whereas if movement includes provision for a The traditional five level hierarchy of streets has. bus route modest gradients are allowable Routes effectively been abandoned principally because it. intended principally for the movement of vehicles placed an over emphasis on the vehicular movement. other than buses may be steeper although where function of the street system The concept of a. very high volumes are anticipated the adverse hierarchy also implicitly carried with it the notion of. effect of steep gradients must be borne in mind one part of the network being more important than. another The network comprises a system of, Function is defined in terms of two prime interlinking streets serving different functions and. components namely the nature and the extent of often serving these different functions differently. demand As such it is the major informant of the, design of the cross section The demand may be for Over emphasis of the importance of one link at the. high speed high volume traffic flows in which cost of another does not only constitute poor design. case the cross section would comprise more than it can place the network as a whole in jeopardy In fact. one moving lane in each direction possibly with a all parts of the network require equal consideration. median between the opposing flows and shoulders To assist designers in developing some understanding. as opposed to sidewalks On the other hand if the of the new classification system Table 7 1 offering a. demand is for predominantly pedestrian comparison between the previous five tier system the. commercial activity very wide sidewalks i e wider Urban Transport Guideline UTG series and that. than would be required merely to accommodate a currently employed is shown below. volume of moving pedestrians would be necessary, to allow for sidewalk cafes roadside vending and It should however be clearly understood that there is. browsing or window shopping While vehicles not a one to one relationship between the current and. would not necessarily be excluded their presence the other classifications The five tier and the UTG. would not be encouraged and speeds would be classification systems are limited to addressing. forced down by having few and narrow lanes and movement in terms of a spectrum of accessibility versus. very short tangent lengths mobility whereas the current classification addresses. all functions of roads and streets Reference should be. Geometric design made to Chapter 5 1 Movement Networks in which. the classification system is comprehensively described. Design is principally concerned with converting to. physical dimensions the constraints introduced by Mixed routes forming part of the movement. planning concepts Ongoing reference to the network classification can be subdivided into higher. chapter on Planning is necessary to ensure that the order middle order and lower order routes. road as ultimately designed matches the intentions Higher order routes would carry higher volumes of. regarding its function It is important to realise that traffic and or accommodate higher levels of economic. the function of the road reserve is broader than activity whereas lower order routes would principally. merely the accommodation of moving traffic which address local and access seeking traffic and. may be either vehicular or pedestrian Although accommodate higher levels of recreational activity. geometric design tends to focus on movement the Middle order routes serve primarily as links between. other functions must be accommodated If the higher and lower order routes It would thus be. designer does not adopt this wider perspective the unwise to regard the appellation of higher order as. most likely consequence would be that the original an invitation to reach for say UTG 5. intention the creation of an urban place that, should be such that people would wish to live work The five tier system subdivided Class 5 streets into a. and play there would be severely compromised further six sub classes two of which could be loosely. Road design should therefore not only accom modate public transport but actively seek to encourage its use Adding embayed bus stops to a route essentially designed for passenger cars does not constitute support for the promotion of public transport Obviously bus routes should be designed with the bus as the design vehicle This selection of design vehicle impacts inter alia on decisions

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