High way and Transportation 2(Lab) LCIV 3034

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High way and Transportation 2(Lab) LCIV 3034

• Instructor Prof. Dr. Shafik Jendia
• Assistants Eng.Mustafa abou foul

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Base of the geometric Design of roads
1-category of roads 2-design speed
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Category of Roads
1-Location (urban roads-rural
roads) 2-Road surrounding ((?????
?????? ???????-????? ????? ?? ?????? 3-Design
function A-conection ????? ??? ?????
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B-collection ????? ??????? ?????? ?? ?????
??????? c-Local ??? ???????
??????? ???? ??????
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Category of Roads
5 Groups (A,B,C,D, E) ???? ????
??? 5 ?? ???? ??????? ???????
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Design Speed (vD)

• Design speed is a selected speed used to
  determine the various geometric design features
  of the roadway, The assumed design speed depend
  on functional classification of highway.
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  ??????? ?????? ?????? ?????? .

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ELEMENTS OF DESIGN

• CROSS SECTION
• SIGHT DISTANCE
• HORIZONTAL ALIGNMENT
• VERTICAL ALIGNMENT

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ELEMENTS OF DESIGN

• CROSS SECTION (???? ??????)

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ELEMENTS OF DESIGN

• CROSS SECTION (???? ??????)
• lanes
• Surface Type
• Cross Slope
• Shoulders

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LANES
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Shoulders
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Surface Type
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Cross Slope
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Sight distance
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What is sight distance?

• Sight distance is the length of highway visible
  to a driver. A safe sight distance is the
  distance needed by a driver on an arterial, or a
  driver exiting a driveway or street, to verify
  that the road is clear and avoid conflicts with
  other vehicles.
• Sight lines must be kept free of objects which
  might interfere with the ability of drivers to
  see other vehicles. Features such as hills,
  curves in the road, vegetation, other
  landscaping, signs, and buildings can reduce
  sight distance.

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Sight distance

• Stopping sight distance
• (????? ?????? ??????? ??????)
• Applicable on all highways
• Passing sight distance
• (????? ?????? ??????? ???????)
• Applicable only on two-lane highways

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Stopping Sight Distance

• Stopping sight distance is defined as the
  distance needed for drivers to see an object on
  the roadway ahead and bring their vehicles to
  safe stop before colliding with the object.
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Stopping Sight Distance

• NOTE
• The sight distance at every point along a roadway
  should be at least that needed for a
  below-average driver or vehicle to stop.
• Stopping sight distance is influenced by both
  vertical and horizontal alignment. For vertical
  sight distance, this includes stopping sight
  distance or passing sight distance at crest
  vertical curves and headlight sight distance at
  sag vertical curves .

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Stopping Sight Distance Sag vertical curves

• Sag vertical curves provide greater stopping
  sight distance during daylight conditions, but
  very short sag vertical curves will limit the
  effective distance of the vehicles headlights at
  night. If lighting is provided at sag vertical
  curves, a design to the driver comfort criteria
  may be adequate.
• The length of sag vertical curves to satisfy the
  comfort criteria over the typical design speed
  range results in minimum curve lengths of about
  half those based on headlight criteria.

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Stopping Sight Distance

• Stopping sight distance is the sum
• 1-The brake reaction distance (????? ?? ?????).
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  ??????? (2.5).
• 2-Breaking distance (????? ??????).
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  ?????? ?????.

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Stopping Sight Distance

• Stopping sight distance is the sum of the brake
  reaction distance and the braking distance .
• Actual stopping distances are also affected by
  road conditions, the mass of the car, the incline
  of the road, and numerous other factors .

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Stopping Sight Distance
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Stopping Sight Distance
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SSD on level roadways

• Brake reaction distance predicated on a time of
  2.5 s deceleration rate of 3.4 m/s2 11.2 ft/s2
  used to determine calculated sight distance.

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SSD on grade

• These adjusted sight distance values are computed
  for wet-pavement conditions using the same design
  speeds and brake reaction times used for level
  roadways in Table1.

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Variation for Trucks

• The recommended stopping sight distances are
  based on passenger car.
• The larger and heavier truck, need longer
  stopping distances from a given speed than
  passenger vehicles.
• BUT
• The truck driver is able to see substantially
  farther beyond vertical sight obstructions
  because of the higher position of the seat in the
  vehicle.

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Passing Sight Distance

• Most roads and many streets are two-lane, two-way
  highways on which vehicles frequently overtake
  slower moving vehicles. Passing maneuvers in
  which faster vehicle move ahead of slower
  vehicles must be accomplished on lanes regularly
  used by opposing traffic. If passing is to be
  accomplished safely , the passing driver should
  be able to see a sufficient distance ahead, clear
  of traffic, to complete the passing maneuver
  without cutting off the passed vehicle before
  meeting an opposing vehicle that appears during
  the maneuver.
• When appropriate, the driver can return to the
  right lane without completing the pass if he or
  she sees opposing traffic is too close when the
  maneuver is only partially completed.

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Passing Sight Distance

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  ???? ??????.

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Passing Sight Distance

• When computing minimum passing sight distances on
  two-lane highways for design use, certain
  assumptions for traffic behavior are necessary,
  some of which offer a wide choice.
• The assumed control for driver behavior should
  be that practiced by a high percentage of
  drivers, rather than the average driver.

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Assumptions

• The overtaken vehicle travels at uniform speed.
• The passing vehicle has reduced speed and trails
  the overtaken vehicle as it enters a passing
  section.
• When the passing section is reached, the passing
  driver needs a short period of time to perceive
  the clear passing section and to react to start
  his or her maneuver.
• Passing is accomplished under what may be termed
  a delayed start and a hurried return in the face
  of opposing traffic. The passing vehicle
  accelerates during the maneuver, and its average
  speed during the occupancy of the left lane is 15
  km/h 10 mph higher than that of the overtaken
  vehicle.
• When the passing vehicle returns to its lane,
  there is a suitable clearance length between it
  and an oncoming vehicle in the other lane.

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Passing Sight Distance

• The minimum passing sight distance for two-lane
  highways is determined as the sum of the four
  distances.

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Passing Sight Distance

• d1 - Distance traversed during perception and
  reaction time and during the initial acceleration
  to the point of encroachment on the left lane.
• d2 - Distance traveled while the passing vehicle
  occupies the left lane.
• d3 - Distance between the passing vehicle at the
  end of its maneuver and the opposing vehicle.
• d4 - Distance traversed by the opposing vehicle
  for two-thirds of the time the passing vehicle
  occupies the left lane, or 2/3 of d2 above.

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• PSD values for different speeds .

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Passing Sight Distance

• NOTES
• For Divided roads, The passing sight distance is
  not available.
• It is not necessary to consider passing sight
  distance on highways or streets that have two or
  more traffic lanes in each direction of travel.
• For roads that have special lane for overtaking,
  The passing sight distance is not available.
• When passing sight distance is not available it
  equals SSD.

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Criteria for Measuring Sight Distance

• Height of Drivers Eye
• Height of Object

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Criteria for Measuring Sight Distance

• Height of Drivers Eye
• For sight distance calculations for passenger
  vehicles, the height of the drivers eye is
  considered to be 1,080 mm 3.5 ft above the road
  surface.
• For large trucks, the driver eye height ranges
  from 1,800 to 2,400 mm 5.9 to 7.9 ft.
• The recommended value of truck driver eye height
  for design is 2,330 mm 7.6 ft above the roadway
  surface.

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Criteria for Measuring Sight Distance

• Height of Object
• For stopping sight distance calculations, the
  height of object is considered to be 600 mm 2.0
  ft above the road surface.
• For passing sight distance calculations, the
  height of object is considered to be 1,080 mm
  3.5 ft above the road surface.

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Sight distance with vertical curves

• The longest distance through which a driver with
  his or her eye height of 1.08 m can see an object
  with a 0.6 m height .

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Sight distance with vertical curves
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Sight distance with vertical curves