Soils and their Classification · 2020. 12. 3. · Shoulder widths will vary according to functional classification, traffic volumes, urban/rural location, curbed/uncurbed, and the

Lecture #1 Cross Section Elements

Highway Lectures Four th Class

Par t #1: - Cross Section Elements

Prepared By Dr. Haider Habeeb Aodah

Thi_ Qar University College of Engineering/Civil Engineering

Department

Slide 2 of 42 Introduction

1) Travel Lanes (Carriageways) �̂�° �} ~ }�*° 2) Cross slop (Camber) ℠7 ��} �71 3) Shoulders � *"�¹ } 4) Medians 877 �1�} �¥℗�} 5) Curbs 87§5*℗�} ¥℗}1° �} 6) Side Slopes 7̂§5*℗�} �171�} 7) Guard Rails 8℗7�⁵ } 8) Sidewalks �̂1 �¹ } 9) Gutters � 7�1 "�} ~ }15� 10) Right of way � 7�7 �} ��° 1 11) Others

Slide 3 of 42 Introduction

FREEWAY AND EXPRESSWAY (Reference #3)

Slide 4 of 42 Introduction

Rural Highway (Reference #3)

1) Travel Lanes (Carriageways), (Pavement)

The type of pavement usually is determined by analysis of the volume

and composition of traffic, the soil conditions, the availability of

materials, the initial cost, the desired service life and the estimated

cost of maintenance.

There are different types of surfacing such as:- i. Flexible pavement type (Asphalt mix).

ii. Rigid pavement (Portland cement concrete).

iii. Concrete pavement bricks (Interlock)

iv. surface treatment on prepared subbase material.

v. Others.

Slide 5 of 42

1) Travel Lanes (Carriageways), (Pavement)

Width of the carriage way or the width of the pavement depends on:-

i. Design volume

ii. Vehicle dimensions

iii. Design speed

iv. Road classification

The width of the carriage way vary between (3.0 m to 3.75 m). For

single lane, the desirable carriage way width recommended is 3.75

m and 3.5 m for multilane.

Slide 6 of 42

1) Travel Lanes (Carriageways), (Pavement) Slide 7 of 42

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2) Cross Slop (Camber)

Camber or cant is the cross slope provided to raise middle of the

road surface in the transverse direction to enable surface water to

drain from traffic lanes and shoulders as quickly as possible .The

objectives of providing camber are:

Surface protection especially for gravel and bituminous roads;

Sub-grade protection by proper drainage;

Quick drying of pavement which in turn increases safety.

Accumulations of water cause hazards by reducing surface friction

and vehicle stability. Good drainage minimizes moisture

Slide 8 of 42

2) Cross Slop (Camber)

Crown is the point which having maximum height on the

carriageway

Cross slope (camber) values for different type of pavement

according to Iraqi Highway Design Manual is given below:-

Slide 9 of 42

3) Shoulders

Shoulder widths will vary according to functional classification,

traffic volumes, urban/rural location, curbed/uncurbed, and the

project scope of work. So, shoulder widths can vary between 1.25

to 3.0 m. The paved shoulder part has the same slop as the

carriageway, but unpaved shoulder has a cross slop 8% . The

following are some of the important functions of shoulders:

provides structural support for the traveled way;

increases highway capacity;

encourages uniform travel speeds;

enhances highway aesthetics;

Slide 10 of 42

3) Shoulders

provides structural support for the traveled way;

provides space for emergency stops;

improves sight distance around horizontal curves;

facilitates maintenance operations;

provides space for pedestrian and bicycle use.

provides support for guardrail and prevents erosion around

guardrail posts;

prevents or minimizes pavement edge dropoffs;

Slide 11 of 42

4) Medians

Medians are provided on divided multi-lane highways to provide a

separation of opposing traffic lanes, a recovery area for out-of-

control vehicles and an area for emergency stops. Besides these

safety benefits, medians also can provide space for: Collecting surface drainage, Refuge for pedestrians at crosswalks, Reduce light glare, Reduce accidents, Installation of traffic control devices and Adding future lanes

The Medians width suggested by Iraqi standard is vary from 3.0 m to 10.5 m according to highway type and classification.

Slide 12 of 42

5) Curbs

Curbs are used on urban and suburban facilities due to control drainage delineate pavement edges prevent the vehicles from leaving the pavement at hazardous point channelize vehicular movements manage access provide separation between vehicles and pedestrians

Slide 13 of 42

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6) Side Slopes

Side slopes are important in maintaining the stability of the

roadbed and pavement structure as well as providing an area for

the safety of errant vehicles. Side slopes are constructed in both fill

(embankment) areas (those falling above the natural ground level)

and cut areas (those falling below the natural ground level).

Cut slop For earth materials

(gravel soil, silt, sand or clay, H≤ 6.0 M)

Side slop equal {H:V = 2:1 to 4:1

(For safety taken 4:1)}

Slide 14 of 42

Cut slop (Reference #2)

6) Side Slopes

For earth materials (gravel soil, silt, sand or clay, H> 6.0 M) Side slop value should be designed according to analysis for slop stability theory and economic materials. For rocky materials side slop depend on the rock quality. See figure below;

Slide 15 of 42

Rural Highway (Reference #2)

6) Side Slopes

Fill slop

Slide 16 of 42

Fill Slop (Reference #2)

6) Side Slopes

Fill slop :- Fills along waterway will be designed as figure below

Slide 17 of 42

Fill slop (Reference #2)

7) Guard Rails

Slide 18 of 42

They are provided at the edge of the shoulder usually when the

road is on high an embankment especially when the height of the

fill exceeds 3 m and at hazard locations:-

High an embankment; Embankment on sharp curve; Water edge; sudden change in alignment; Deep ditch in cutting; Others dangerous place.

They serve to prevent the vehicles from running off the embankment. Guard stones painted in alternate black and white are usually used. They also give better visibility of curves at night under headlights of vehicles.

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8) Sidewalks

Slide 19 of 42

That portion of the highway cross section separated from the roadway and constructed for the use of pedestrians.

Sidewalks are an integral part of city roads, sometimes provided in rural areas.

In residential areas the sidewalk width

varies between 1.2 to 2.4 m. The side walk

should be separated from the traveled way

with a curb and planted strip of minimum

0.6 m width.

Side walk (Reference #5)

9) Gutter

Slide 20 of 42

A street gutter is a depression running parallel to a road designed to collect rainwater flowing along the street and divert it into a storm drain. The max. depth of gutter is o.3 m. The min. longitudinal grade is 0.5%. The min. width of gutter is 0.5 m. The max. width of gutter is 1.0 m. The surface cross full should be 10% .

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10) Right of way

Slide 21 of 42

Right of way is the width of land acquired for the road, along its alignment. It should be adequate to accommodate all the cross-sectional elements of the highway and may reasonably provide for future development

The right of way width is depends on:- The category of the highway and width of roadway Height of embankment or depth of cutting. Side slopes of embankment or cutting. Sight distance considerations. Drainage system and their size which depends on topography etc.

Right of way is used for:- Future expansion; Safety and Maintenance.

In general the right of way ≥ 80 m, for highway roads the right of way ≈ 100 m.

10) Others

Slide 22 of 42

Vertical Clearances

Vertical Clearnce (Reference #2)

10) Others

Slide 23 of 42

Horizontal Clearances

Horizontal Clearance (Reference #2)

10) Others

Slide 24 of 42

Bus-bays Bus bays are provided by recessing the kerbs for bus stops. They

are provided so that they do not obstruct the movement of vehicles in the carriage way. They should be at least 75 meters away from the intersection so that the traffic near the intersections is not affected by the bus-bay.

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Questions - ?

References 1) Delaware Department of Transportation, (2004), “Road Design Manual”,

Delaware State. USA.

2) Ministry of Housing and Construction, (2004), “Highway Design Manual”,

Republic of Iraq.

3) Bureau of Design and Environmental Manual, (2010), “Cross Section Elements”,

Illinois, USA.

4) Tom V. Mathew and K V Krishna Rao, (2007), “Introduction to Transportation

Engineering”, The Indian Institute of Technology Bombay, India.

5) Ali Alwash and Harith Ajam, (2010), “Lectures of Highway Engineering”,

Babylon University, Iraq.

Lecture #1� Cross Section Elements �Slide Number 2Slide Number 3Slide Number 41) Travel Lanes (Carriageways), (Pavement)1) Travel Lanes (Carriageways), (Pavement)1) Travel Lanes (Carriageways), (Pavement)2) Cross Slop (Camber) 2) Cross Slop (Camber) 3) Shoulders3) Shoulders4) Medians5) Curbs6) Side Slopes6) Side Slopes6) Side Slopes6) Side Slopes7) Guard Rails�8) Sidewalks�9) Gutter10) Right of way�10) Others10) Others10) OthersQuestions - ?References