This document discusses junction design. It begins by defining key terms like junction, conflict point, and roundabout. It then covers factors that affect junction load and the types of vehicle movements at junctions. Design considerations for selecting junction types are outlined, including traffic delay and operating costs. Traffic light design and phases are described. Conflict points and areas are analyzed, and ways to reduce conflicts at junctions are discussed. Finally, the document analyzes basic design considerations for junctions, including sight distance.

1. CHAPTER 7
JUNCTION DESIGN

2. LEARNING OUTCOMES
7.4 Analyze basic
design for the
junction
7.3 Apply the concept
of conflict point in
reducing the conflict at
the junction
7.2 Understand the
concept of junction
design, conflict area and
roundabout
7.1 Know the
fundamental concept
of junction

3. 8.1 Know the fundamental concept of junction
Define junction
List the factors
that affect
junction load
Name the types
of movement at
a junction
State the
selection factors
of junction types
Describe traffic
light design and
phases

4. Junctions or intersections
refer to the land area where
two or more highways meet
or intersect with or cross
each other.
Junctions are designed so
that drivers can cross traffic
streams or move from one
traffic stream to the other in
an attempt to change
direction of movement
This activity must be done
with minimum delay but
maximum safety. This can
be ensured by means of
proper geometric design
and implementation of the
appropriate traffic control
measures
Definition
The physical
characteristics of the road.
For example, road width ,
number of lanes crossing
type and others .
composition of traffic and
the capacity of the vehicle.
Examples of heavy vehicles
from the type of vehicle .
Environmental conditions .
For example, weather ,
impaired pedestrian and
parking , the physical
characteristics of the driver
and others .
Factors
that affect
junction
load

5. Types of movement at
a junction
TURNING
CROSSING
MERGING
DIVERGING
WEAVING

6. Factors selection of junction types
• Delay of queuing is the delay line experienced by the driver due to the
interaction of the vehicle.
• When demand exceeds the capacity of traffic flow at the intersection is
maximum, can be accommodated by junction there will be a delay .
• Selection of intersection will be affect the delay .
• The different intersection will be produce different delay line.
• Therefore , in the selection of the intersection , the intersection of which
resulted in the delay of queuing minimum should be choose
Traffic
Delay
(Queuing)
• Geometry delay, is a delay caused by the geometry design of the
intersection/junction .
• It will be delay even if no vehicles in the intersection/junction
• Geometry delay it’s depends on the geometry design of the
intersection/junction and the vehicle speed acceleration and deceleration
at the intersection/junction.
• Good design can reduce the intersection geometry delay.
Geometry
Delay
Continue…….

7. Continue…………
• In the selection of the intersection , the costs caused by delays and operating
costs should be considered.
• Operating costs of vehicles depending on the vehicle speed , distance travelled
and the type of intersection .
• The costs that must be taken into account is the cost of petrol , tires ,
maintenance , depreciation , etc. due to the intersection .
• In addition, other costs to consider is the cost of time and accident costs .
• In addition , environmental factors ( costs of noise, air pollution by gas emissions
and vehicle emissions ) and aesthetic aspects should also be taken into account
in the selection type of intersection
Operating
costs of
vehicles at
intersections
• Some types of intersection requires a large space .
• The cost of acquisition of land in cities is very high .
• This is an important factor in the selection of the intersection .
• Review the cost of benefits shall be made ​​between the level of traffic
flow would be accommodated by junction within junction design life
and costs of providing a kind of intersection .
Factors
Land
Acquisition

8. Traffic light
types
• Fixed Time Signal
• Vehicle Actuated
Signal
The
method of
determining
the period
• Sequences
• Phases
• Factors that should
be considered to
determine the time
period .
Phases
• Time cycle 2
phases
• Time cycle 3
phases
• Time cycle 4
phases
Traffic Light
Design &
Phases

9. Long interval time for
a show the signal in
one cycle is fixed.
Instantiations rights of
way in accordance
with a predetermined
schedule
long-time green, red,
yellow is "fixed" in one
cycle
Based patterns, traffic
history
Optimum cycle time, Co
= (1.5L + 5)/(1-
y).Minimum cycle time of
25 seconds, maximum
120 seconds.
Fixed
Time
Signal
Features:
Phases of the signals
"irregular"
Phase welcomed actual
traffic demand registered
sensors
Junction capacity can be increased
because the the arm junction that
has a number of high traffic
demand will be given the green
time is longer.
Delay is minimized,
especially during non-peak
Effective use of the crossing
which required more than two
phases
The problem of high demand on
the 'major road' and the
'platoon', causing delay to
'minor road'
Vehicle
Actuated
Signal
Features:
TRAFFIC LIGHT TYPES

10. Sequences
• The sequence or sequences common in
Malaysia is a traffic light Green - Yellow - Red.
Phase
• Methods of controlling traffic through the traffic lights at
the time of separation can avoiding traffic conflicts.
• Separation of conflicting traffic flow in accordance with
the specified time is known as a phase.
• Phase traffic is part of the cycle time allocated to one or
more eligible traffic flow through the intersection.
THE METHOD OF DETERMINING THE PERIOD

11. Factors that should be considered to determine the time period
1. The composition of traffic
• Because of the various sizes of vehicles using the crossing, then
it must be synchronized with the passenger vehicle unit (PCU-
passenger car units).
The table shows the various types of vehicles Coefficient Factors
Relative to Vehicle Passengers
Vehicles Type Coefficient
Factors (pcu)
1 Motorcycle 0.33
1 Car 1.00
1 Heavy Vehicle 1.75
1 Light Vehicle 2.00
1 Bus and lorry 2.25
1 Bicycle 0.22

12. 2. Saturated Flow (S)
• Saturated flow is the maximum number of vehicles that can cross
the stop line without breaking the driveway intersection during a
green signal to continue. Saturated flow unit is a passenger
vehicles per hour (pcu / hour).
• For saturated flow value (S),When the road width (w)> 5.5 m,
S = 525 W
• When the road width (w) <5.5 m,
Schedule determine Saturated Flow, S
Road width (m) 3.00 3.50 4.00 4.50 5.00 5.50
Saturated Flow
(pcu/hr)
1850 1875 1975 2175 2550 2900

13. 3. The use of Interchange Rates
• To get the intersection utilization rate (Y), the flow rate versus
saturated flow in a phase (y) shall be calculated first.
• y = q / S,
where,
y = the flow rate versus saturated flow
q = actual flow of traffic (pcu / hr)
S = Saturated Flow (pcu / hr)
• Y value for a given phase is a the largest ymax than any branch
in that phase. Therefore,
• Value Y = ymax phase A + B + ymax phase ... .. <0.85 (ok)

14. 4. Green time, green efficient time and time lost
• When the light turned green, the traffic flow does not begin
abruptly. The initial vehicle takes to accelerate from rest to get
right of way. A few seconds after that, then the occurrence of
saturation in that phase.
• If the yellow signal, the number of vehicles dropped from the
saturation to zero as soon as the red signal starts.
• For each phase, it has its own time and total loss of all the
time lost every phase known as lost time (L). Lost time
occurred during start-up and during stops.

15. PHASES
Time cycle 2 phases
Time cycle 3 phases
Time cycle 4 phases

16. Describe the term of
traffic light circulation
phase design
Explain the types of
junction
Draw the conflict point
and the conflict area at a
junction
Discuss the
characteristics and the
types of roundabout
Understand the concept of junction design, conflict
area and roundabout

17. Describe term of traffic light circulation phase design
1. Lost Time (l )
• Is at the intersection of time is wasted due to exchange of phase and
also the movement of vehicles.
2. Actual Green Time (gfasa)
• Actual green time is allocated in phases based on the critical flow
ratio of each of 'y‘
• Effective green time of each phase is given by
Gfasa = (y Critical/Y) X G
• Actual green time for the phase is regarding to
gfasa = Gfasa + (l - k)
• When actual green time of each phase was determined the time
division green, yellow and a red time for each phase can be shown
in time diagram.
3. Effective Green Time (G)
• This is the time available for moving traffic, taking into account the
time that was stolen from the yellow time and lost time to start
moving. The value of effective green time can be obtained by, G for
each round is
G = Co - L

18. 4. Red Time (r).
Time signal is indicated by the traffic light make a movement to
stop the vehicle.
5. Amber/Yellow Time (k).
Yellow is the time allocated to vehicle acquire traffic light for
drivers to be prepared to stop or start the movement of the
vehicle. Usually the yellow time is 3 seconds.
6. Cycle Length.
Is the amount of time a lap time of green, yellow and red for
the traffic light. Often the maximum cycle time of 2 minutes and
a minimum of 6 to 8 seconds.
7. Interval Green Time (I)
This is the time between the end of the green in one phase and
the start of the green in the next phase. Usually the minimum
green time is between 5 seconds or 4 seconds if using modern
lighting controller. If there is high pedestrian flow at the
intersection, the time between the green can be extended.

19. Types of junction
Grade Junction Interchange

20. Grade Junction
• When two road meet or cross at the same elevation, at-grade
junctions are created. These junctions come in a variety of
configuration and varying levels of complexities. Nevertheless,
all junctions evolve from six basic shapes
• Figures below show basic shapes of at – grade junctions

21. • There are many varying junction types, in detail, but they can
be broken down into six basic types.
1. Uncontrolled non-priority junctions.
2. Priority junctions.
3. Priority junctions with traffic islands.
4. Roundabouts.
5. Traffic signals.

22. Interchange/Grade separation
• Grade separated intersection or interchange is
characterized by the absence of crossing conflicts
since traffic streams cross each other at different
elevations and hence provides the highest level of
traffic safety at junctions.
• The basic elements of an interchange are shown in
figure .

23. Figure : Basic elements in an interchange.

24. • Grade separated intersections are primarily built
to satisfy the requirements of full access control
especially on expressways. Traffic delay is
virtually eliminated except when the interchange
itself has reached capacity.
• Vehicles merge and diverge on speed change
lanes. Despite it’s high capacity and excellent
traffic safety records, they are expensive to build,
take up huge land space and require physical
structures such as bridge, ramps and
embankments.
• Their layout can be confusing to motorists unless
backed up with adequate road signage. A
complete guide on the fundamentals and design
of interchanges is available in a JKR publication
(JKR 1987).

25. • In general, the basic interchange type and forms can
be categorized into the followings :
(a) 3-legged interchange:
Trumpet or Tee-interchange

26. Directional Interchange
(a) 4-legged interchange:
Diamond interchange

27. Cloverleaf interchange.
Directional interchange

28. (c) Multi-legged Interchange:
Rotary interchange

29. 8.2.3 Conflict
point and the
conflict area
at the
junction
Conflict is a
possibility of a
collision between
vehicles.
Conflicts in an
intersection is
dependent on the
movement of traffic
and vehicle speed.
The combination of
movements
(movements merge,
split/diverging and
crossing) this creates
confusing at the
intersection of
movement and lead
to conflicts following:
1) Merging conflicts
2) Split/diverging
conflict
3) Cross Conflict
4) The conflict of the
above merge conflict

30. The points of conflict at the intersection

31. ROUNDABOUT
• Roundabout is considered a series of priority road junction
consists primarily of one-way.
• Roundabout operates as a one-way system round around
the middle of the island and is controlled by the input path
GIVE WAY signs.
• Priority is given to the traffic moving from the right.
• Operational efficiency depends on the network driver's ability
to react to the existing space between vehicles on the road
preference.
• The different levels of network traffic flow accordingly if:
i. Loads greater than the system priority intersections.
ii. The need to make a turn - U (Uturn). It is important for
traffic management.
iii. There is a high stream the right turn.
iv. The exchange of road types (to reduce the speed).
Characteristics and The Type Of Roundabout

32. TYPES OF
ROUNDABOUT
ORDINARY
ROUNDABOUT
MINI
ROUNDABOUT
TWIN
ROUNDABOUT
INTERCHANGE
ROUNDABOUT
HOOP
SIGNAL
ROUNDABOUT

33. TYPES OF ROUNDABOUT
a. Ordinary Roundabout
• Has 3 or 4 infusion.
• They often have flowering lane.
• Has the island of drop in centre has a diameter greater than
or equal to 4m.
• Suitable for new construction, the intersection at the end of
the four-lane two-way road and to change direction at the
intersection of the new road.

34. b. Mini roundabout
• The diameter is between 2 - 4m.
• It is located in an area with a low direction of road
speed (the speed limit to 50 kph).
• Suitable for mini roundabout intersection in the city
when space is a problem.

35. c. Twin Roundabout
• Represent two regular or mini roundabout at the intersection
of the same or adjacent connected by a short path.
• It is useful to control the traffic that has asymmetrical
approach or unusual.

36. d. Interchange
• It allows at least one traffic flow through the crossing without
barriers while other movements are controlled by the
community.
• Interchange often used in highways in the city and consists of
a four-lane two-way road.
• It is also often held in high-capacity roads and high-speed
approach and in places that have high pedestrian flow.

37. d. Roundabout Hoop
• It is a two-way system round the great aim of every
path is provided with a circle 3 - way direction or
control traffic lights.
• It is appropriate at some point to solve traffic control
problems that have had input on site.

38. e. Signal Roundabout
• Roundabout is controlled by traffic lights.
• Traffic entering the intersection from one or more
of the approach road controlled by traffic lights.
• Roundabout this type has been demonstrated can
increase network capacity, especially when
crowded that have high traffic flow.

39. Concept Of Conflict in Reducing The
Conflict At The Junction
• Potential conflicts of intersection depends on:
i. The approach road crossing
ii. The lanes behind the stop line
iii. type of traffic control
iv. channelling rate
v. traffic movement allowed
• At the intersection of four common, namely single lane in each
direction, there are a total of 32 points of conflict (slide no 30).
The number of conflicts that so many very dangerous, but can
be reduced by means of traffic management, such as:
i. vehicles out of turn to the right direction of a road.
ii. Makes one-way road.
iii. Converts crosses the intersection of four to staggered.

40. • A common method of controlling conflict is through
priority control by directing vehicles on the road
STOP or GIVE WAY to traffic on major roads.
• If a large volume of vehicles on the roads is very
high, as a great delay promoting techniques to
reduce conflict by providing a circle and traffic
lights.
• Conflicts can also be minimized by using
channeling. In the circle, avoided direct conflict
with channel vehicle in certain lanes and enforce
the rules GIVE RIGHT OF WAY TO THE
VEHICLE.
• At signalized intersections, conflicts are minimized
through appropriate arrangement of phase.
Reducing The Conflict At The Junction

41. Analyze Basic Design For The Junction
1. Sight Distance.
• The intersections, there are two main types of sight distance;
i. Heading Sight Distance
ii. Departure Sight Distance
Heading Sight Distance
Sight distance heading mean there is a need to allow the driver to
stop his vehicle safely behind the stop line, ie without trespassing
into the area of intersection.
S = [ (Vt)/3.6 ] [ {1/(2a)} x (V/3.6)2 ]
V = vehicle design speed (km / h)
t = time of decision, reaction and response and braking time
(seconds).
a = Maximum deceleration that does not trigger discomfort (m / s).
Namely 0.2 g = 0.2 x 9.81 = 1.96 m/s2 @ 7.06 km/h

42. • Time design - time of decision, reaction and
response and braking time (seconds).
i. Signalized intersection
t = 10 s in rural areas.
t = 6 s in urban areas
ii. Crossing stop control
t = 2 s (time decision ignored)

43. • Consider a section of rural freeway with a design
speed of 70 km/h at the intersection without traffic
lights. On a section of level terrain, what the safe
heading sight distance must be provided.
Solution :
S = [ (Vt)/3.6 ] [ {1/(2a)} x (V/3.6)2 ]
= [ (70 x 2)/3.6 ] [ {1/(2 x 1.96)} x (70/3.6)2 ]
= 3751 m

44. ii. Departure Sight Distance
Sight distance departure mean there is a need to
enable the vehicle in the lane to cross the intersection
safely without disrupting the smooth movement of
vehicles on the road.
Figure 1 : Departure Sight Distance

45. • Vehicles 'A' priority - vehicles 'B' which is a small road must stop at
the stop line.
• Vehicles 'A' move in design speed to cross the intersection safely
• 'B' must be able to look at the 'A' at a distance 'AC' is sufficient.
• The distance required by the 'B' to cross without interrupting
transmissivity the journey 'A' is 'BD' equal to :
T = (D + W + L).
D = distance between the side of the pavement
W = Width of pavement
L = length of the vehicle (P = 5m, SU = 10m and WB-50 = 15m)
• Departure sight distance it’s :
d = [V/3.6] [J + ta]
V = Design speed
J = Total reaction time [ 2.5 s (rural roads) and 1.5 s (urban road) but
the design standards for reaction time is 2.5 s ]
ta = The time required to accelerate and crossed the distance T
(Figure 2).

46. Figure 2 : Acceleration Performance Vehicle Design

47. What is the departure sight distance for a section
of urban freeway with a design speed of 80 km/h on
a 4 legs intersection. Where D = 3m, W = 7m and L
= category P (5m).
Solution :
T = (D + W + L)
= 3 + 7 + 5
= 15 m
d = [V/3.6] [J + ta]
= [ 80/3.6] [1.5 + 5]
= 144 m

48. 2. Design Optimal Circulation
Time For Two-Phase at a
Junction.
Calculation ……..

49. THANK YOU