Highway Engineering I
Dr. Nahla Hussein
nahla.alaswadko@uod.ac
Third Year Students
1st semester, 2018 - 2019
1 Lecture 1
Highway Engineering I
Time per week: 4 hours (Theory: 2hrs, Tutorial: 1hr and
Practical: 1hr)
Student's responsibility and assessment pattern:
– Quizzes, Class attendance, class works and home works (20%)
– Mid-Semester exam (20%)
– Final Exam (40%)
– Practical (20%)
2
Topics to be covered
Introduction/general
Cross section elements
Route surveying and planning
Earthworks estimation
Geometric design
Sight distance on horizontal curve
Sight distance on vertical curve: Sag and creast vertical curves
Vertical curve alignment: Symmetrical and unsymmetrical curves
Horizontal curve alignment: Simple circular, compound, reverse and
transition curves
Superelevation and widening
Intersections and interchanges
3
Recommended References
A policy on Geometric Design of Highways and Streets, by
American Association of State Highway and Transportation
Officials (AASHTO), 1990.
Highway Engineering, by Paul H. Wright and others, sixth
edition, 1996.
Transportation Engineering and Planning, by C. S. Papacostas
and P. D. Prevedouros, third edition, 2001.
Highway Capacity Manual (HCM), Transportation Research
Board (TRB), BY ITE, 2000.
Transportation Engineering, by C. Jotin Khisty and B. Kent
4 Lall, second edition, 1990.
Introduction
Transportation engineering: is the application of technology and
scientific principles to the planning, functional design, operation, and
management of facilities for any mode of transportation in order to provide
for the safe, rapid, comfortable, convenient, economical, and
environmentally well-suited movement of people and goods.
Transportation modes are:
Highway transport
Railway transport
Airway transport
Waterway transport
5 Pipe transport
What does highway design involve?
Geometric design:
– Cross-section elements: number and width of lanes, divided (with
median) or not, drainage structures, overtaking lanes etc.
– Horizontal and vertical alignments
– Design of intersections and interchanges
Pavement and surfacing design
Road furniture: lighting, landscaping, guide posts, guard rails,
traffic islands, traffic signals, signs
Road delineation: line marking, raised pavement markers etc.
6
Highway Geometric Design
Road geometric design is the selection of road features and
dimensions.
Cross-section elements Horizontal alignment
(straights and curves)
Vertical alignment
(grades and vertical
Interchange curves)
7
Objectives of Highway Design
Safety for all users; geometric parameters
Efficiency; operational and economic
Sustainability; social, environmental, natural
and economic
8
Objectives of Highway Design
Safety: Geometric parameters
Users’ expectations (no surprises)
– Related to operating speed (e.g. flat vs.
mountainous terrain i.e. large vs. small
curves)
Consistency in design standards
– Along same route and within the whole
network
Consider all possible users when
selecting design parameters;
– cars, trucks, motorcyclists, cyclists,
9 pedestrians
Objectives of Highway Design-
Efficiency (operation and economics)
Design standards must be related to traffic
volumes and route importance
Widest Avenue in the world (100m) in
Argentina
Monash Freeway/Australia
10 http://weburbanist.com/2007/12/03/7-urban-wonders-of-the-world-amazing-and-record-setting-city-roads-and-streets/
World’s most curved road- San Francisco, USA
http://weburbanist.com/2007/12/03/7-urban-wonders-of-the-world-amazing-and-record-setting-city-roads-and-streets/
11
Objectives of Highway Design-
Sustainability (environmental, social, natural and economic)
Optimize route selection Sound barriers
– Minimise earthworks
– Minimise impacts on water streams and habitat
– Protection of tradition sites
Provide sustainable drainage systems
– Collect storm water
– Waste traps and waste separators
Aesthetics
Use of surface materials that minimise noise
Providing smooth travel and reducing
congestion and delay
Minimise energy consumption; e.g. using
digital signs
12
Highway Design Elements
Overall location of a route
Road Classification / standards
Design vehicles and traffic volumes
Operating speed & terrain
Adequate cross section
Drainage requirements
Horizontal and Vertical alignments and their coordination
Earthworks
Provision of overtaking opportunities
13
Functional Classification of Highway
• Freeway or expressway: full
control of access, long distances and
high design speeds.
• Arterial (distribution): moderate
design speeds.
• Sub-arterial (transition roadways
or ramps)
• Collector : intermediate design
speeds, serving border areas and
shorter trips.
• Local (access roads or streets):
property access (main aim) and
lower design speeds
14
Geometric Design Input Parameters
Traffic volumes and types
Design vehicle
Operating speed and Design speed
Sight distance
15
Traffic Volumes
Average Annual Daily Traffic (AADT) =veh/day
for road geometric design.
Peak hour volume for intersection design.
Traffic counter/classifier
16
Traffic Types
Cars Registered 2008 2013
Average annual
growth 08/13
Trucks no. no. %
Passenger vehicles 11,803,536 13,000,021 2.0
Buses Campervans
Light commercial
44,790 54,101 4.0
2,288,216 2,717,673 3.6
Bicycles vehicles
Light rigid trucks 105,726 131,147 4.6
Heavy rigid trucks 305,184 325,998 1.4
Motorcycles Articulated trucks 79,132 90,904 2.9
Non-freight
Pedestrians carrying vehicles
21,808 22,986 1.1
Buses 80,581 93,034 3.0
Scooters Motor cycles 567,569 744,732 5.8
17
Design Vehicles
Horizontal and Vertical Alignment
– Cars
– Check for truck needs < 2m wide
Intersections
– Cars, number of lanes
– Trucks turning templates 2.5m wide, 12.5m long 2.5m wide, 19m long
Pavement design
– Trucks
18
Operating Speed
Operating Speed is the measured 85th percentile
speed of cars, on a particular geometric element or
length of road, at a time when traffic volumes are low
i.e. when drivers are free to choose the speed at
which they travel. 85% of car drivers will travel at
or below this speed and 15% travel faster.
19
Design Speed
Design Speed is the speed that is used to determine
and coordinate the safe dimensions of road geometric
elements (horizontal curves radii, vertical curves lengths, cross-
section elements).
Design Speed must be > Operating speed which
must be > posted speed limit
20
Highway Design Elements
Cross-section Elements
21
Types of road cross-sections
Rural and urban
Carriageway:
– Dual carriageway (Divided by a median)
– Single carriageway (undivided) 2-lane 2-way
4-lane 2-way divided
undivided urban road
Number of lanes urban road
– Two-lane Two-way
One lane in each direction
– Four-lane Two-way
Two lanes in each direction
4-lane 2-way divided
rural road
22
Types of road cross-sections
4-lane 2-way divided 2-lane 2-way
urban road undivided urban road
4-lane 2-way divided 2-lane 2-way
rural road undivided rural road
23
Six lane two way divided urban road with 2 single lane service roads.
24
Typical road cross-section in rural
highway
Flat on a left hand curve
Straight and flat
25 Flat on a right hand curve
Wire rope safety barrier, both sides Wire rope barrier, one side
Guardrail safety barrier, both sides Guide posts
Median: Functions and dimensions
27
Right of Way
Right of Way (R.O.W) or Road Reserve
=
Land available for building the road
28
Elements of an Urban Road
Single carriageway (Two-lane Two-way)
Traffic lane Traffic lane
Pavement
Cross Section
29
Divided Urban Road
Dual Carriageway (Four-lane Two-way or Six-lane Two-way)
Cross Section
30 Plan
Divided Urban Road
Dual Carriageway & service roads
Six-lane Two-way with 2 service roads (single lane)
Cross Section
Plan
31
Elements of a Rural road cross-section
Single carriageway (Two-lane Two-way Rural Road)
Cut
Fill
32
Rural road cross-section
Divided Rural Roads (Dual Carriageway)
Rural road cross-section
33
Cut (road below natural surface)
Fill (road above natural surface)
Road in fill- on embankment
Road in cut
Road in fill
34
Cut & Fill Batters
• Batter slopes depend on slope stability, safety, appearance,
maintenance considerations, landscaping requirements and
need to reduce erosion.
• Defined as the ratio of horizontal distance to unit height in
the vertical direction e.g. 4 to 1 (4:1).
35 Fill slope/Batter Cut slope/Batter
Drains Details
1) Table Drain: is a v, trapezoidal or parabolic shaped
surface drain located immediately adjacent to the edge of a road. The
side slope of a table drain should be 6 to 1 where possible, but can be as
steep as 4 to 1.
36
Drains Details
2) Catch Drain (Ditch): is a small to moderate depression created
along side roadways to channel water or fields. A ditch can be used
for drainage, to drain water from low-lying areas, or to channel water
from a more distant source for plant irrigation.
37
Elements of Urban cross-sections
Purposes and Functions
Traffic lanes: Provide for vehicular movement, through, turn and
service
Pavement: carry traffic load and protect the subgrade
Crossfall (normal crossfall on straight): directs surface water into
drains
Pit: collect surface/rain water from pavement and footway
Nature strip: separates pedestrian from vehicles and provides
aesthetics and easy access to underground utilities
Footpath: provide for easy and comfortable pedestrian movement
Footway: footpath + nature strip
Median (depressed or raised): separates opposing traffic
movements, accommodates elevation variation between the two
38 carriageways
Elements of rural cross-section-
purposes and functions
Traffic lanes: Provide for vehicular movement,through,turn and service
Pavement: carry traffic load and protect the subgrade
Median (depressed) (with median shoulders and verges)
Crossfall: directs surface water into drains
Shoulder: side support for the pavement, a clear space for broken
down vehicle and for improved sight distance
Verge: space for installing signs and guide posts
Batter (cut or fill):the slope of earthworks embankment or cuttings and
controlled by type of material, safety and maintenance requirements
Table drain: captures surface and subsurface water and from batters
and catch drains
Catch drain: captures surface water and from high ground water to
39 prevent batter erosion.
