Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
assignment done on bridge and special problem structures
Typology: Lecture notes
1 / 34
This page cannot be seen from the preview
Don't miss anything!
Ambo University
Ambo University
HHiT
School of Civil and Environmental
Engineering
Dept. of Civil Engineering
Course Instrutor: Eyob Mekonnen (Ass.Prof) Nov, 2021
1. Introduction^ 1. Introduction 2. Type of
Interchanges
and selection
Criteria
2. Type of
Interchanges
and selection
Criteria
Using AASTO and ERA manuals
Consideration
Consideration
I. Interchanges are divided into two functional classes
1.Access/Service/ , Serve the community by providing access to freeways
2.System Interchanges, are the nodes of freeway network, linking the
individual freeways into a cohesive unit.
******** System ---Freeway to freeway Connection---Directional
******* Service ----Freeway to arterial or Collector----diamond, Cloverleaf,
etc.
(from freeway to towns, cities, etc)
Used where intersection can
handle left turns
each quadrant for all
turning movements
originates/terminates at
either at-grade intersection
with cross street or
junction with frontage road
Full and partial
Apply where left turns cant be served
(possibly physically) at an intersection
and there is available ROW.
Loops accommodate LTS.
Comparison of Cloverleaf and diamond
Interchange
Advantages of
Diamond over
Cover leaf
Requires less RW
Requires less RW
Left turns travel less
distance
Left turns travel less
distance
High-speed
exit/entrance
High-speed
exit/entrance
No weaving section
No weaving section
Advantages of
Cloverleaf over
Diamond
Left turns merge at
acute angles
Left turns merge at
acute angles
Higher left turn capacity
Higher left turn capacity
Turning Vehicles may
not have to stop
Turning Vehicles may
not have to stop
Don’t need median/signs
to prevent wrong way
entrance
Don’t need median/signs
to prevent wrong way
entrance
Warrants For Interchanges And Grade
Separations
1.Design designation.
The determination to develop a highway with full control of
access between selected terminals becomes the warrant
for providing highway grade separations or interchanges
for all intersecting roadways crossing the highway.
Although access control , provision of medians , and
elimination of parking and pedestrian traffic are
important, the separation of grades on freeways provides
the greatest increment of safety.
ng 6305, Advanced Geometric Design, MSc in Highway Engineering
Once it has been decided to develop a route as a freeway, it
should be determined whether each intersecting highway
will be terminated, rerouted , or provided with a grade
separation or interchange.
The chief concern is the continuous flow on the major road.
If traffic on the minor road will cross the freeway, a grade
separation or interchange is provided.
Thus, an intersection that might warrant only traffic signal
control, if considered as an isolated case, will warrant a
grade separation or interchange when considered as a
part of a freeway.
3.Reduction Of Crash Frequency And Severity
frequency of serious crashes. If inexpensive methods of
reducing crashes are likely to be ineffective or impractical,
a highway grade separation or interchange may be
warranted.
course, also warrant interchange facilities. In addition to
the reduction in crash frequency and severity, the
4. Site topography.
At some sites, grade-separation designs are the only type of
intersection that can be constructed economically.
The topography at the site may be such that, to satisfy
appropriate design criteria, any other type of intersection
is physically impossible to develop or is equal to or greater
than the cost of a grade-separated design.
