GEOMETRIC DESIGN Flashcards
Divisions of Highway Design
- Geometric Design
- Intersection Design
- Highway Drainage Design
- Pavement Design
- Earthworks
- Road Facilities
- Roadway lighting
One of the divisions of highway design concerned with the positioning of the physical elements of the roadway according to standards and constraints
Geometric design of highway
Three Main Parts of Geometric Design
- Alignment (Horizontal – Plan)
- Grade line (Vertical - Profile)
- Cross section
The route of the road, defined as a series of horizontal tangents and curves
Alignment (Horizontal –Plan)
The vertical aspect of the road, including crest and sag curves, and the straight grade lines connecting them
Grade line (Vertical -Profile)
It shows the position and number of vehicle and bicycle lanes and sidewalks, along with their cross slope or banking
Cross section
It shows drainage features, pavement structure and other items outside the category of geometric design
Cross section
Geometric Design Elements
- Design parameters (speed, vehicle, volume)
- Sight distance (Visibility)
- Horizontal Alignment (curves, radius of curvature, super-elevation)
- Vertical Alignment (vertical curve, gradient)
- Combination of Horizontal and Vertical Alignment
- Cross Section
- Drainage
Design speeds ranging from ______ for local streets, and 50kph or higher for ______
30 to 50 kph : Collector Streets
Rural arterials other than expressways should be designed for speeds of _________, depending on terrain, driver expectancy
60 to 120 kph
Urban arterials should be designed for speeds of _______.
50 to 100kph
Expressways should be designed for speeds not less than ______.
80 kph
At _________ a rider or driver has less time to react to a situation and therefore there is the likelihood that an error will result in a crash.
Higher running speeds
Momentum and kinetic energy of a vehicle increases rapidly with ______.
Speed
The distance at which a driver of a vehicle can see an object ahead of time.
Sight Distance
Types of Sight Distance
- Stopping (Non-Passing) Sight Distance
2.Decision Sight Distance
3.Passing Sight Distance
Available distance on a roadway to enable a vehicle traveling at the design speed to stop before reaching a stationary object.
Stopping Sight Distance
Applied where only one obstacle must be seen in the roadway and dealt with.
Stopping Sight Distance
Distance required for a driver to initiate and complete safely and efficiently the maneuver of an unexpected or otherwise difficult-to-perceive information source or hazard.
Decision Sight Distance
Applied where numerous objects, pedestrians, vehicles or design features, complex control or complex surrounding land use, and topographic conditions must be addressed by the driver
Decision Sight Distance
The sight distance long enough to enable a vehicle to overtake and pass another vehicle on a two lane highway without interference from opposing traffic
Passing Sight Distance
Distance required for a driver to see a sufficient object to complete the passing maneuver without cutting off the passed vehicle in advance of meeting an opposing vehicle appearing during maneuver.
Passing Sight Distance
The passing vehicle accelerates during the maneuver, during the occupancy of the left lane, at about _____ higher than the overtaken vehicle.
16 kph
Assumption for PSD: The overtaken vehicle travels at a ___________ (slower than design speed)
Uniform speed
Break reaction distance is predicted on a time of ____ and deceleration rate of ____ based on the minimum design for stopping sight distance
2.5 s : 3.4 m/s^2
Types of Terrain
- Flat
- Rolling
- Mountainous
Considered for turning
Minimum Radius of Curvature
Considered in Banking
Super elevation
Considered for future traffic flowrate
Design Volume
Design Criteria for Geometric Design
- Minimum radius of curvature
- Design Volume
- Design Speed
- Sight Distances
- Number of Lanes
- Superelevation
