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Cive 461 > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

Definition of an intersection

A

An intersection is the area shared by 2 or more roads

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2
Q

Function of an intersection

A

the function of the intersection is to provide change for route direction

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3
Q

Intersections are of two types

A

AT grade intersection (requires traffic control system)
Grade separated or an interchange:
consists of structures to provide cross flow of the major traffic movements at different levels without interruption

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4
Q

Conflict points of an intersection

A

1-merging
2-weaving
3-diverging
4-crossing

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5
Q

potential conflict points for a 4 point intersection

A

are 32 look at page 11 and draw it

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6
Q

Why do we use traffic control

A

we use traffic control in order to reduce number of conflict points

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7
Q

Types of intersection control

A

1-)Yield signs
2-)stop signs
3-)intersection channelization
4-)traffic signals

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8
Q

Interchanges

A

grade separated intersections

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9
Q

Functions of interchange

A

1-) provide grade separation between two or more traffic arterials
2-) provide easy transfer of vehicles from one arterial to another

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10
Q

Warrants of an interchange ( When is an interchange needed)

A

1-)High traffic volumes
2-)reduction of bottlenecks and spot congestion
3-)road user benefits
4-)safety improvements

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11
Q

The configuration of an interchange depends on the following

A

1-)Site topography
2-)Traffic projections,(how the movements are at the intersection)
3-)land availability
4-)environmental impacts

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12
Q

first interchange type

A 
Diamond interchange 
WE HAVE
 #DIAMOND INTERCHANGE 10 10 10
#TUDI TIGHT/COMPRESSED URBAN DIAMOND INTERCHANGE
#DDI DIVERGING DIAMOND INTERCHANGE 8 8 2
#SINGLE POINT URBAN INTERCHANGE 8 8 8
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13
Q

When we use diamond interchange (responsible for drawing and conflict points)

A

we use diamond interchange when there is a freeway/non-freeway intersection

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14
Q

When we use diamond interchange, the flow on the freeway is uninterrupted

A

true

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15
Q

on the arterial of the diamond interchange we have four left turns

A

true

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16
Q

the diamond interchange is the less costly interchange

A

true

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17
Q

diamond interchange does not support heavy traffic on the surface street or on the ramps or on the left turns

A

true

18
Q

what is the ramp function on the diamond interchange

A

the function of the ramp is to connect the freeway to the surface street also it functions as a transition from low speeds to freeway speeds

19
Q

Diamond interchange variations

Tight/compressed urban diamond interchange (TUDI)

A

Used in urban areas where there is limited right-of-way

20
Q

Diamond interchange variations
Double crossover/Diverging diamond interchange (DDI)
Drawing is required

A

The two directions of traffic on the non-freeway road cross to the opposite sides. Two signalized intersections with two phases each. Requires additional signage and pavement markings.

21
Q

Diamond interchange variations.
Single point urban interchange (SPUI) .
Drawing is required.

A

Single signalized intersection that allows the two left turn movements to proceed simultaneously.

22
Q

Second interchange type

drawing is required

A

Full cloverleaf interchange

23
Q

Function of the full cloverleaf interchange

A

Allows non-stop full access between two busy roads.

24
Q

In full cloverleaf interchange , the traffic merges and weaves but it doesnot cross at grade

A

true

25
Q

the full cloverleaf interchange is typically used where a freeway intersects a busy surface street

A

true

26
Q

Characteristics of full cloverleaf

A 
# common interchange
# Grade separation for intersecting roadways
#All 8 turning movements are accomplished free of intersections with crossing traffic
27
Q

Difficulties of full cloverleaf interchange

A

1) Requires large areas of land (land cost)
2) left turning vehicles execute 270 degrees right turn (sharp curve, steep grade)
3) we have weaving and merging at high speeds
4) weaving on main line results in reduced speed on main line

28
Q

Weaving in a full directional cloverleaf

A 
#Weaving occurs between the adjacent loops of a cloverleaf interchange (See picture)
# The extent and impact of weaving depends on traffic volume, freeway number of lanes, distance between the ramps, and speed.
29
Q

How we can eliminate the weaving
see picture
collector-distributor

A

weaving can be eliminated by adding a collector and distributor roads which divert entering or exiting traffic to these roads

30
Q

How we can eliminate the weaving
see picture
directional ramps

A

we can remove weaving by replacing left turn loops with directional ramps which result in cloverstack interchange and total removal of weaving

31
Q

THIRD interchange type is partial cloverleaf interchange,

drawing is required

A

functionally it is equivalent to a diamond and it is also known as a folded diamond where one or more ramps are folded into a loop on the opposite side of the surface street.

32
Q

Partial cloverleaf interchange may have two ramps

A

True

33
Q

In partial cloverleaf interchange loops can be placed in different quadrants to fit topography and traffic patterns.

A

true

34
Q

fourth interchange type

directional interchange

A 
#it is freeway to freeway interchange
# accommodates heavy left turn movements by a 90 degrees turns to the left.
# movements occurs at design speed of the expressway
# reduce / eliminate weaving
# it has higher number  of required structures
35
Q

Fifth interchange type
three leg intersection
Y-intersection

A

one grade separation

36
Q

Sixth interchange type

T-intersection (trumpet intersection)

A 
# it has three approaches
# only one movement requires 270 degree turn, others are accomplished at 90 degrees.
37
Q

Interchange selection considerations

A 
#traffic forecasts
#physical consideration (space, number of intersections..))
#Economical
#SAFETY  
#Aesthetics
# environmental impact
38
Q

picture page 40 must memorize

A

See it

39
Q

Name 4 assessments of interchanges

A 
#level of service 
#Safety consideration
# Delays at signalized intersections 
# Weaving, merging and diverging on the freeway.
40
Q

page 42 memorize

A

true

41
Q

look at pics from page 43 till end

A

true

Cive 461 (14 decks)

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