High way and Transportation 2(Lab) LCIV 3034

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

Base of the geometric Design of roads

1-category of roads

2-design speed

Category of Roads1-Location (urban roads-rural roads)2-Road surrounding (( - البناء من خالية منطقة بالسكان مأهولة منطقة

3-Design function A-conection والمراكز الكبري المدن بين الربط ببعضها B-collection الطرق من للمرور المجمعة الطرق الرئيسة c-Local المشاة وطرق السكنية المناطق طرق

Category of Roads 5 Groups

(A,B,C,D, E)

رقم صفحة 5أنظر الهندسي التصميم كتاب من

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.

دون بأمان عليها يسير أن للسائق يمكن سرعة أقصي هي , كالطقس المحيطة الظروف تكون ان بشرط حوادث وقوع

. مواتية المركبة وحالة :الرتباطه جدا مهم امر التصميمية السرعة اختيار مالحظة

ومسافة االفقية المنحنيات اقطار وانصاف الطريق بسعةوغيرها . الرؤية

ELEMENTS OF DESIGN CROSS SECTION

SIGHT DISTANCE

HORIZONTAL ALIGNMENT

VERTICAL ALIGNMENT

ELEMENTS OF DESIGNCROSS SECTION ( الطريق (قطاع

ELEMENTS OF DESIGNCROSS SECTION ( الطريق (قطاع lanes

Surface Type

Cross Slope

Shoulders

لطريق عرضي قطاع من نموnزجبحارتين

LANES

Shoulders

Surface Type

Cross Slope

Sight distance

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.

Sight distance Stopping sight distance

) الوقوف ) الالزمة الرؤية مسافة Applicable on all highways

Passing sight distance) للتجاوز ) الالزمة الرؤية مسافة

Applicable only on two-lane highways

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.

لكي طريق علي تواجدها من البد مسافة اقل هيسرعة باقصى تسير سيارة يوقف ان السائق يتمكن

علي موجود بعائق االصطدام خطر دون بأمان تصميميةالطريق.

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 .

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 vehicle’s 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.

Stopping Sight Distance Stopping sight distance is the sum 1-The brake reaction distance ( الفعل رد .(مسافة

للعائق السائق رؤية لحظة من العربة تسيرها التي المسافة هيالفرامل ) تشغيل وزمن الفرامل عمل بدء لحظة .(2.5حتي

2-Breaking distance ( التوقف .(مسافة. التام الوقوف حتي الفرامل توقيع لحظة من الفرملة المسافة هي

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 .

Stopping Sight Distance

Stopping Sight Distance

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.

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.

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.

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.

Passing Sight Distance :سريعة عربة تتخطي لكي كافية مسافة اقل هي تعريف

الحارة في بمرورها وذلك أمامها تسير بطيئة عربةخطر دون الحارة نفس الي العودة ثم األخري

وتسير المعاكس االتجاه في قادمة بعربة االصطدامالعربة مضايقة دون للطريق التصميمية بالسرعة

. امامها تسير التي البطيئة

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.

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.

Passing Sight Distance The minimum passing sight distance for two-lane

highways is determined as the sum of the four distances.

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.

PSD values for different speeds .

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.

Criteria for Measuring Sight Distance Height of Driver’s Eye

Height of Object

Criteria for Measuring Sight Distance Height of Driver’s Eye For sight distance calculations for passenger

vehicles, the height of the driver’s 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.

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.

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 .

Sight distance with vertical curves

Sight distance with vertical curves