Title: High way and Transportation 2(Lab) LCIV 3034
1High way and Transportation 2(Lab) LCIV 3034
- Instructor Prof. Dr. Shafik Jendia
- Assistants Eng.Mustafa abou foul
2Base of the geometric Design of roads
1-category of roads 2-design speed
3Category of Roads
1-Location (urban roads-rural
roads) 2-Road surrounding ((?????
?????? ???????-????? ????? ?? ?????? 3-Design
function A-conection ????? ??? ?????
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B-collection ????? ??????? ?????? ?? ?????
??????? c-Local ??? ???????
??????? ???? ??????
4Category of Roads
5 Groups (A,B,C,D, E) ???? ????
??? 5 ?? ???? ??????? ???????
5Design 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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6ELEMENTS OF DESIGN
- CROSS SECTION
- SIGHT DISTANCE
- HORIZONTAL ALIGNMENT
- VERTICAL ALIGNMENT
7ELEMENTS OF DESIGN
- CROSS SECTION (???? ??????)
-
8ELEMENTS OF DESIGN
- CROSS SECTION (???? ??????)
- lanes
- Surface Type
- Cross Slope
- Shoulders
9????? ?? ???? ???? ????? ???????
10LANES
11Shoulders
12Surface Type
13Cross Slope
14Sight 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.
16Sight distance
- Stopping sight distance
- (????? ?????? ??????? ??????)
- Applicable on all highways
- Passing sight distance
- (????? ?????? ??????? ???????)
- Applicable only on two-lane highways
17Stopping 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. - ?? ??? ????? ???? ?? ??????? ??? ???? ??? ?????
?????? ?? ???? ????? ???? ????? ???? ???????
????? ??? ??? ???????? ????? ????? ??? ??????.
18Stopping 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 .
19Stopping 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.
20Stopping Sight Distance
- Stopping sight distance is the sum
- 1-The brake reaction distance (????? ?? ?????).
- ?? ??????? ???? ?????? ?????? ?? ???? ???? ??????
?????? ??? ???? ??? ??? ??????? ???? ?????
??????? (2.5). - 2-Breaking distance (????? ??????).
- ?? ??????? ??????? ?? ???? ????? ??????? ???
?????? ?????.
21Stopping 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 .
22Stopping Sight Distance
23Stopping Sight Distance
24SSD 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.
25SSD 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.
26Variation 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.
27Passing 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.
28Passing Sight Distance
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???? ??????.
29Passing 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.
30Assumptions
- 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.
31Passing Sight Distance
- The minimum passing sight distance for two-lane
highways is determined as the sum of the four
distances.
32Passing 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 .
34Passing 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.
35Criteria for Measuring Sight Distance
- Height of Drivers Eye
- Height of Object
36Criteria 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.
37Criteria 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.
38Sight 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 .
39Sight distance with vertical curves
40Sight distance with vertical curves