PPT: Introduction to Intersection Control - Notes | Study Transportation Engineering - Civil Engineering (CE)

 Page 1


Introduction to intersection control
(Objectives)
Understand why some sort of control is
essential to allocate ROW at intersections
Understand there is hierarchy of intersection
control (Traffic signal is NOT a cure-all)
Learn how to check sight distances available
at an intersection
Learn about the warrants for stop and yield
controls
Learn how to check traffic signal warrants
(No need to read pages 389-392 because it
will not be in the 2000 MUTCD.)
Page 2


Introduction to intersection control
(Objectives)
Understand why some sort of control is
essential to allocate ROW at intersections
Understand there is hierarchy of intersection
control (Traffic signal is NOT a cure-all)
Learn how to check sight distances available
at an intersection
Learn about the warrants for stop and yield
controls
Learn how to check traffic signal warrants
(No need to read pages 389-392 because it
will not be in the 2000 MUTCD.)
Conflict points at unsignalized intersections
T intersection
Crossing = 3
Merging = 3
Diverging = 3
Total = 9
4-leg intersection
Total = 32
Page 3


Introduction to intersection control
(Objectives)
Understand why some sort of control is
essential to allocate ROW at intersections
Understand there is hierarchy of intersection
control (Traffic signal is NOT a cure-all)
Learn how to check sight distances available
at an intersection
Learn about the warrants for stop and yield
controls
Learn how to check traffic signal warrants
(No need to read pages 389-392 because it
will not be in the 2000 MUTCD.)
Conflict points at unsignalized intersections
T intersection
Crossing = 3
Merging = 3
Diverging = 3
Total = 9
4-leg intersection
Total = 32
Hierarchy of intersection control
Intersection Control Options: How much judgment can drivers safely
exercise to avoid collisions? Three levels of control are available.
Level I Passive control – basic rules of the road apply
Ø No control
Ø Guide signs only
Ø Warning sings with or without guide signs
Level II Assignment of ROW to major street or rotational ROW
Ø YIELD control (roundabouts are in this category)
Ø Two-way STOP control
Ø All-way STOP control
Level III Positive alternate assignment of exclusive ROW
Ø Traffic signals: 2-phase, multiphase
Ø Traffic control agent/officer
Page 4


Introduction to intersection control
(Objectives)
Understand why some sort of control is
essential to allocate ROW at intersections
Understand there is hierarchy of intersection
control (Traffic signal is NOT a cure-all)
Learn how to check sight distances available
at an intersection
Learn about the warrants for stop and yield
controls
Learn how to check traffic signal warrants
(No need to read pages 389-392 because it
will not be in the 2000 MUTCD.)
Conflict points at unsignalized intersections
T intersection
Crossing = 3
Merging = 3
Diverging = 3
Total = 9
4-leg intersection
Total = 32
Hierarchy of intersection control
Intersection Control Options: How much judgment can drivers safely
exercise to avoid collisions? Three levels of control are available.
Level I Passive control – basic rules of the road apply
Ø No control
Ø Guide signs only
Ø Warning sings with or without guide signs
Level II Assignment of ROW to major street or rotational ROW
Ø YIELD control (roundabouts are in this category)
Ø Two-way STOP control
Ø All-way STOP control
Level III Positive alternate assignment of exclusive ROW
Ø Traffic signals: 2-phase, multiphase
Ø Traffic control agent/officer
Assessing the viability of basic rules-
of-the-road
Primary prerequisite for safety under basic rules-of-the-road: Sight distance
must be adequate for the driver before he is accountable for full responsibility for
his action. è The first thing you want to check is whether adequate SSD is
available at the intersection. This must be satisfied before traffic volume concerns
come into consideration.
a
b d
a d
b
A
B
-
=
-
From the similarity of triangles:
b d
ad
d
A
A
B
-
=
Page 5


Introduction to intersection control
(Objectives)
Understand why some sort of control is
essential to allocate ROW at intersections
Understand there is hierarchy of intersection
control (Traffic signal is NOT a cure-all)
Learn how to check sight distances available
at an intersection
Learn about the warrants for stop and yield
controls
Learn how to check traffic signal warrants
(No need to read pages 389-392 because it
will not be in the 2000 MUTCD.)
Conflict points at unsignalized intersections
T intersection
Crossing = 3
Merging = 3
Diverging = 3
Total = 9
4-leg intersection
Total = 32
Hierarchy of intersection control
Intersection Control Options: How much judgment can drivers safely
exercise to avoid collisions? Three levels of control are available.
Level I Passive control – basic rules of the road apply
Ø No control
Ø Guide signs only
Ø Warning sings with or without guide signs
Level II Assignment of ROW to major street or rotational ROW
Ø YIELD control (roundabouts are in this category)
Ø Two-way STOP control
Ø All-way STOP control
Level III Positive alternate assignment of exclusive ROW
Ø Traffic signals: 2-phase, multiphase
Ø Traffic control agent/officer
Assessing the viability of basic rules-
of-the-road
Primary prerequisite for safety under basic rules-of-the-road: Sight distance
must be adequate for the driver before he is accountable for full responsibility for
his action. è The first thing you want to check is whether adequate SSD is
available at the intersection. This must be satisfied before traffic volume concerns
come into consideration.
a
b d
a d
b
A
B
-
=
-
From the similarity of triangles:
b d
ad
d
A
A
B
-
=
Rule 1: Both vehicles have at least
one safe SSD to the collision point
Step 1: Assume that Vehicle A is located one safe SSD from the collision
point.
Step 2: Based on the assumed position, determine the location of Vehicle B
when it first becomes visible. Call it d
B(act)
Step 3: Rule 1 requires Vehicle B to have one safe SSD. Call it d
B(min)
.
Step 4: If d
B(act)
/ d
B(min)
, then adequate SSD for basic rules-of-the-rule has been
provided. Otherwise, violated and under Rule 1, not safe.
( ) G f
S
t S d
A
A A
±
+ =
30
468 . 1
2
b d
ad
d
A
A
B
-
=
( ) G f
S
t S d
B
B B
±
+ =
30
468 . 1
2
(min)