Geometric Design Flashcards
Divisions of Highway Design
Geometric Design
Intersection Design
Highway Drainage Design
Pavement Design
Earthworks
Road Facilities
Roadway lighting
is 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
is the route of the road, defined as a series of horizontal tangents and curves.
Alignment (Horizontal –Plan)
is the vertical aspect of the road, including crest and sag curves, and the straight grade lines connecting them.
Grade line (Vertical -Profile)
shows the position and number of vehicle and bicycle lanes and sidewalks, along with their cross slope or banking.
Cross section
also show drainage features, pavement structure and other items outside the category of geometric design.
Cross section
Geometric Design Elements
Cross Section
Combination of Horizontal and Vertical Alignment
Design parameters (speed, vehicle, volume)
Drainage
Sight distance (Visibility)
Horizontal Alignment (curves, radius of curvature, super-elevation)
Vertical Alignment (vertical curve, gradient)
Design speeds ranging from ______ for local streets, and _______ for collector streets
30 to 50 kph ; 50 kph or higher
______ other than expressways should be designed for speeds of 60 to 120 kph, depending on terrain, driver expectancy
Rural arterials
________ should be designed for speeds of 50 to 100kph
Urban arterials
_______ should be designed for speeds not less than 80 kph.
Expressways
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
Based from AASHTO Greenbook:
Height of Driver’s Eye
_______ = (for passenger cars)
________ = (for large trucks)
1.08 m ; 2.33 m
Based from AASHTO Greenbook:
Height of Object
_______ = (for stopping)
_______ = (for passing)
0.60 m ; 1.08 m
Based from DGCS Volume 4 (3.6.1.5):
Height of Driver’s Eye
_______ = (in all cases)
1.15 m
Based from DGCS Volume 4 (3.6.1.5):
Height of Object
______ = (for stopping)
______ = (for passing)
0.15 m ; 1.40 m
Types of Sight Distance
Stopping (Non-Passing) Sight Distance
Decision Sight Distance
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
It is substantially greater than the stopping sight distance.
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 overtaken vehicle travels at a
uniform speed (slower than design
speed)
The passing vehicle trails the overtaken vehicle as it enters a
passing section
The ______ requires a short period of time to perceive whether a clear passing section is available and to start maneuvering
driver
The passing vehicle accelerates during the maneuver, during the occupancy of the left lane, at about ________ than the overtaken vehicle.
16 kph higher
There is a suitable _______ length between the passing vehicle and unknown
clearance
