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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 Passing Sight Distance NOTES: For Divided roads ... – PowerPoint PPT presentation

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Title: High way and Transportation 2(Lab) LCIV 3034


1
High way and Transportation 2(Lab) LCIV 3034
  • Instructor Prof. Dr. Shafik Jendia
  • Assistants Eng.Mustafa abou foul

2
Base of the geometric Design of roads
1-category of roads 2-design speed
3
Category of Roads
1-Location (urban roads-rural
roads) 2-Road surrounding ((?????
?????? ???????-????? ????? ?? ?????? 3-Design
function A-conection ????? ??? ?????
?????? ???????? ??????
B-collection ????? ??????? ?????? ?? ?????
??????? c-Local ??? ???????
??????? ???? ??????
4
Category of Roads
5 Groups (A,B,C,D, E) ???? ????
??? 5 ?? ???? ??????? ???????
5
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.
  • ?? ???? ???? ???? ?????? ?? ???? ????? ????? ???
    ???? ?????, ???? ?? ???? ?????? ??????? ??????
    ????? ??????? ??????.
  • ?????? ?????? ?????? ????????? ??? ??? ???
    ???????? ???? ?????? ?????? ????? ?????????
    ??????? ?????? ?????? ?????? .

6
ELEMENTS OF DESIGN
  • CROSS SECTION
  • SIGHT DISTANCE
  • HORIZONTAL ALIGNMENT
  • VERTICAL ALIGNMENT

7
ELEMENTS OF DESIGN
  • CROSS SECTION (???? ??????)

8
ELEMENTS OF DESIGN
  • CROSS SECTION (???? ??????)
  • lanes
  • Surface Type
  • Cross Slope
  • Shoulders

9
????? ?? ???? ???? ????? ???????
10
LANES
11
Shoulders
12
Surface Type
13
Cross Slope
14
Sight distance
15
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.

16
Sight distance
  • Stopping sight distance
  • (????? ?????? ??????? ??????)
  • Applicable on all highways
  • Passing sight distance
  • (????? ?????? ??????? ???????)
  • Applicable only on two-lane highways

17
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.
  • ?? ??? ????? ???? ?? ??????? ??? ???? ??? ?????
    ?????? ?? ???? ????? ???? ????? ???? ???????
    ????? ??? ??? ???????? ????? ????? ??? ??????.

18
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 .

19
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.

20
Stopping Sight Distance
  • Stopping sight distance is the sum
  • 1-The brake reaction distance (????? ?? ?????).
  • ?? ??????? ???? ?????? ?????? ?? ???? ???? ??????
    ?????? ??? ???? ??? ??? ??????? ???? ?????
    ??????? (2.5).
  • 2-Breaking distance (????? ??????).
  • ?? ??????? ??????? ?? ???? ????? ??????? ???
    ?????? ?????.

21
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 .

22
Stopping Sight Distance
23
Stopping Sight Distance
24
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.

25
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.

26
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.

27
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.

28
Passing Sight Distance
  • ??????? ??? ????? ????? ??? ????? ???? ?????
    ???? ????? ???? ?????? ???? ??????? ?? ??????
    ?????? ?? ?????? ??? ??? ?????? ??? ??? ????????
    ????? ????? ?? ??????? ??????? ????? ???????
    ????????? ?????? ??? ?????? ?????? ??????? ????
    ???? ??????.

29
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.

30
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.

31
Passing Sight Distance
  • The minimum passing sight distance for two-lane
    highways is determined as the sum of the four
    distances.

32
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.

33
  • PSD values for different speeds .

34
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.

35
Criteria for Measuring Sight Distance
  • Height of Drivers Eye
  • Height of Object

36
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.

37
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.

38
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 .

39
Sight distance with vertical curves
40
Sight distance with vertical curves
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