06 CE 122 Intersection Design & Analysis

8/13/2019 06 CE 122 Intersection Design & Analysis

1/21

Intersection Design & Control

CE 122 Traffic & Highway EngineeringCollege of SCEGEMapua Institute of Technology (MIT)


2/21

Introduction

Intersections - play an important role in any networksystem.

- points where traffic flow converges and

where direction of travel changes.

Category of Intersection Shape Type of Structure Type of Operation


3/21

Intersection CategoryShape - refers to the configuration of the intersection and

would depend largely on the number of legs.- simpler shape and lesser number of legs


4/21

Intersection CategoryType of Structure most of the intersections are either designed

as at-grade intersection or grade separation such as flyoversor interchanges.- type of intersection depends largely on the extent ofimprovement in terms of easing congestion or reducingtraffic accident


5/21

Intersection CategoryType of Operation rules and regulation applied to given

intersection depend largely on the type of control which is inoperation at that intersection.

main objective is to simplify traffic flow (reduce number ofconflicts of vehicles).

- unchannelized or channelized (simplified movement ofvehicles- unsignalized or signalized (reduces crossing conflicts).


6/21

Basic Intersection Design PrinciplesWhen designing or improving intersection, it is very important to

follow some basic principles to avoid costly mistakes (lack ofintersection capacity and accident-prone.


7/21

Basic Intersection Design Principles


8/21

Intersection Design ElementsTurning Geometry

-The primary purpose of intersection is to provide change in thedirection of travel (either to go straight or turn left or turn right).- turning geometries are direct, semi-direct, and indirect (direct ishighly preferred).


9/21

Intersection Design ElementsCombination of Direct, Semi-direct and Indirect Elements:


10/21


11/21

Design Elements of an Intersection Approach

For smaller intersection, a simple curve may be adequate for design ofintersection corner and turning roadway. However, for large intersection, themost common type is three-centered curve shown above.


12/21

Methods of Control of IntersectionConflicts - often occur at intersection.

- the more the number of legs an intersection has, the more thenumber of conflicts.

- classified as merging, diverging, or crossing conflicts.


13/21

Methods of Control of Intersection


14/21

Methods of Control of Intersection

Categories of Intersection Control:

A. Unsignalized

B. SignalizedC. Grade Separation


15/21

Unsignalized Intersection ControlUnsignalized

- When 2 minor roads intersect, traffic may be assumed to arrive atany approach of the intersection in random fashion. In this case, signal may not be necessary but some form of control must be employed to ensure safety.

When no clear defined priority for intersection:Right of Way Rule when 2 vehicles arrive at the same time at the

intersection, the vehicle on the right has the priority. (It does not depend on thesize of the vehicle right of weight)

When there is clear defined priority for intersection:

Use of YIELD or STOP Sign.


16/21

Unsignalized Intersection ControlRotary or Roundabout

- Another form of unsignalized intersection that works best when thenumber of turning vehicle is almost equal to the number of through vehicle- All vehicles move counterclockwise in one-fashion way- When traffic signals cost proved costly, roundabout is a goodalternative.


17/21

Unsignalized Intersection ControlU-Turn Slots

- very similar to roundabout except that it favors a particular road, which is assumed to be the major road.- has been implemented at several intersections within Metro Manila.


18/21

Signalized Intersection ControlSignalized

- control of traffic intersection by traffic signal is done by separation intime i.e., conflicts between opposing or merging streams are prevented bygiving the right of way to a given direction.


19/21

Signalized Intersection Control


20/21

Grade SeparationGrade Separation

- Eliminates the problematic crossing conflicts of the differentmovements of vehicles.- Flyovers, underpass, or full-blown interchanges are some of theexamples of grade separation- They provide the safest and most efficient method of control but

definitely the most costly and sometime unaesthetic.


21/21

End

06 CE 122 Intersection Design & Analysis

Documents

Transcript of 06 CE 122 Intersection Design & Analysis