PPT On Geometric Design of Roads
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Presentation Transcript:
1. Geometric Design of Roads2. Introduction
Geometric design is an important aspect of highway design
Visible dimensions of roadway
Different elements in geometric design of roads and highways
The safe, efficient and economic operation is governed by the good geometric design standards
The design engineers has to see the following aspects:
Adequate geometric design in planning a highway facility : Volume and composition of traffic should be the basis of design
3. Introduction
Faulty geometrics are costly (rectification of errors)
The design should be consistent (standards should be compatible with each other)
The design should have all the aspects (signs, markings, proper lighting, intersections, etc.)
The highway should be considered as an integral part of environment
The design selection : initial cost of construction, total transportation cost and road user cost should be minimized.
Safety should be built into the design elements
The design should enable all road users (motor vehicles, animal drawn vehicles, cyclist and pedestrians)
4. Geometric Design of Roads
Deals with visible dimensions of a roadway and is dictated by:
Requirements of traffic
Horizontal and vertical alignments
Sight distances
Cross-section components
Lateral and vertical clearances
Intersection treatment
Control of access
5. Elements involved in Geometric Design of Highways
Cross sectional elements
Width of pavement, formation and land, the surface characteristics and cross slope of pavement
Sight distance considerations
Horizontal curves, vertical curves, intersections governs the safety of highways
Horizontal alignment details
Change in road direction, type of horizontal curve, superelevation, extra pavement width, transition curves
6. Elements involved in Geometric Design of Highways …
Vertical alignment details
The gradients and vertical curves
Design of road intersections needs adequate knowledge of traffic engineering
Summary:
Highway geometrics are greatly influenced by the topography, locality, traffic characteristics and the requirements of design speed
The factors which control the geometric design requirements are speed, road user and vehicular characteristics, design traffic, traffic capacity and benefit-cost considerations
7. Design Controls and Criteria
Design speed
Topography
Traffic factors
Design hourly volume and capacity
Environmental and other factors
8. Design speed
Important for economic operation and safety
Considerable variation in speed depending on drivers and kind of vehicle.
Value selected should accommodate nearly all demands and should not fail under severe or extreme cases
Design speed is determined for design and correlation of physical features of highway that influence vehicle operation
Maximum safe speed that can be maintained when conditions are so favorable that design features of highway govern.
Design speed must be correlated with terrain conditions and highway class.
9. Suggested design speeds in kmph for urban streets in India
Arterial………………………. 80
Sub-arterial ………………… 60
Collector street ……………. 50
Local street ………………… 30
10. For more info please refer our ppt
Thanks.
