Town Planning
MODULE IV – ROADS & TRAFFIC STUDIES
MODULE V – MODERN TRANSPORTATION SYSTEM
Lecture by – Ar. Swati Agrawal
Road Junctions or Intersection
The term Junction or Intersection is used to indicate the location
where two or more roads meet or cross one another at the same
or different elevation.
The factors to be considered while making
selection for a particular type of road junction
are;
1. Availability of means of
traffic control.
2. Degree of traffic congestion.
3. Funds available.
4. Number of intersecting streets or
roads.
5. Volume and nature of traffic.
Factors considered in design and operation
1. Angle of crossing
Types of Intersections
2. Camber
3. Channelizing 1. At grade intersections
- All paved or unchannelized intersections
4. Entry speeds - Channelized intersections
5. Gradient - Round about or rotaries
6. Importance of roads
7. Kerbs 2. Grade separated intersections
- Direct ramp
8. Pedestrian traffic - Semi-direct ramp
9. Simplicity - Indirect ramp
10. visibility
At-grade Intersections
It indicates the road junction at same
elevation.
The traffic movements like merging,
diverging crossing, and weaving are
carried out at the same level
The unchannelized intersection
are paved for the whole area
and there is no restriction to
vehicles to use any part of the
intersection area.
Unchannelized Intersections
Channelized Intersections
To handle large volume of traffic and to channelize the turning traffic
introduction of traffic island is done.
The space at a road junction over which traffic is allowed to move is
known as traffic island
Channelized intersections for four streets
Channelized Intersections
Channelized intersections for three streets
Roundabouts or rotaries
A Roundabout or rotary is a specialized form of at-grade
intersection and it consists of a central island surrounded by the
roads forming the junction
Unidirectional circular
movement at the intersection
1. Elliptical
2. Tangent type
3. Turbine top
Elliptical Roundabouts or rotaries
Tangent Type Roundabouts or rotaries
Turbine Type Roundabouts or rotaries
Design of rotary
1. Design speed
2. Radius at entry
3. Radius at exit
4. Radius of the central
island
5. Weaving length
6. Width of
carriage way at
entry and exit
7. Entry and exit
angles
8. External curb line
Design rotary elements -
1. Design speed –
• It should be passed with low speed which will results the safety without any collision
• Speed restriction borad should be provided on the road towards rotary intersection
2. Shape of central Island –
• The shape should not contain any corners
• It should be formed by curves to allow the comfortable rotations around it
• The shape is dependent upon number of roads meeting at that junction
• The shapes generally provided are circular, elliptical, turbine and tangential.
3. radius of Rotary roadway –
• Radius of roadway dependent upon the shape of central island and frictional force
If it is circular shape, radii are similar at all points and if it is elliptical or tangent radii is
different at different points.
Design rotary elements -
4. Weaving angle and distance–
• The weaving angle should be small but minimum of 15deg is maintained
• The weave length should be at least four times the width of weaving section
5. Width of carriageway at entry and exit –
• Width of carriage way at entry and exits is dependent of volume of traffic in
that particular region or area.
• Min. width of 5 metres should be maintained for rotary intersections.
6. Width of Rotary roadway –
• the width should be equal to the effective width of weaving section
7. Curves at entrance and exit
• Entry curve radius can be provided as same as radius of central island
• The vehicle accelerates at exists hence the radius of curve at exit should be
greater than the radius of curve at entrance.
Grade Separated Intersection
A grade Separated intersection is the arrangement of taking one road over and
under by means of bridge. It is also known as a flyover junction.
The direct The Semi-direct The indirect
interchange ramp interchange ramp interchange ramp
involves diverging involves diverging involves diverging
to right to left to left
side and merging side and merging side and merging
from right side from right side from left side
Cloverleaf Interchange
• A clover leaf interchange is a two – level interchange in which
left turns are handled by ramp roads.
• To go left (in right – hand traffic), vehicles first continue as one
road passes over or under the other, then exit right onto a one-
way three – fourths loop ramp (270deg) and merge onto the
intersecting road.
• It is also a four leg interchange and is used when two highways
of high volume and speed intersect each other with
considerable turning movements.
• The main advantage of cloverleaf intersection is that it provides
complete separation of traffic, as well as high speed at
intersections can be achieved. Disadvantage is that large area
of land is required.
Clover Leaf Interchange
It avoids all the right hand movements which are the major source of
accidents.
Diamond Interchange
• A diamond interchange is a common type of road junction,
used where a freeway crosses a minor road.
• It uses less space than most types of freeway interchange,
and avoids the interweaving traffic flows that occur in
interchanges such as cloverleaf.
• These are most effective in area where traffic is light
• Diamond interchange is a form of four-leg interchange
found in the urban locations where major and minor roads
crosses.
• The important feature of this interchange is that it can be
designed even if the major road is relatively narrow.
Diamond Interchange
Rotatory Interchange
The rotary in such case
functions like the collector
and distributor of traffic as
shown in arrows.
Trumpet Interchange
• Trumpet interchanges have been used where one
highway terminates at another highway
• These involve at least one loop ramp connecting traffic
either entering or leaving the terminating expressway
with the far lanes of the continuous highway.
• The principal advantages are low construction cost and
are useful for highways as well as toll roads
Three-way interchange or T-intersection or Trumpet
The three way intersection is
utilized where there are only
three approaches to the
interchange.
With single bridge
Three-way interchange or T-intersection or Trumpet
Limitation of grade
separated Intersections
-Costly to construct
- Requires considerable land
area
Delta or Y-intersection
with three bridges
Traffic Control Devices
In order to control, regulate, and guide traffic it is necessary to have
suitable traffic aids or devices known as traffic control devices
Following are the basic requirements for use of traffic control
device;
1. It must convey clear and simple meaning.
2. It must command attention.
3. It must command respect of road users.
4. It must give adequate time for response. Road markings
5. It must justify necessity. Road signs
Traffic signals
Speed brakers
Road Certain links, patterns, words, symbols
Markings or reflectors on the pavement, kerbs, side of
island
'
Road Signs
As per provisions of the Indian
Motor Vehicle Act and IRC Code,
the road signs can be classified in
following three categories
1. Guide or informatory signs
2. Regulatory or mandatory signs
3. Warning or cautionary signs
Guide or
informatory
signs
Road Signs
Regulatory
or mandatory
signs
Warning or
cautionary
signs
Speed Breakers
-A speed breaker is a hump surface across the roadways.
-It has a rounded shape with width greater than the base of most of
the vehicles where there is decreased variation in sensory stimuli
and at location speed control are desired
Assignment -
Support your answers with neat sketches where ever required.
Q.1 What is Traffic Planning? Explain its aims and objectives.
Q. 2 Explain different traffic surveys which help in traffic study.
Q. 3.Explain reasons for Traffic Congestion. What are the factors which are responsible for
Traffic Congestion? Explain disadvantages of Traffic Congestion. What measures should be taken
Individual
to avoid Traffic Congestion?
Q.4. Define Traffic Volume, Traffic density and Traffic Capacity.
Q. 5. Explain functions of roads. Define and explain classification of urban roads.
Q. 6. Explain factors considered in design and operation of road junctions What are types of
Intersections?
Q. 7 explain Traffic Control Devices.
A2 sheet showing different types of road sections and intersection with detail sketches of road
Group
types. (Group)
Mass & rapid Transportation
System
• BRTS – Bus rapid Transit System
• LRTS – Light Rail Rapid System
• MRTS – Metro Rail Transit System
BRTS-Bus Rapid Transit System
• It is a bus-based public transport
system designed to have much
more capacity, reliability and
other quality features than a
conventional bus system.
• A BRT system includes roadways
that are dedicated to buses, and
gives priority to
buses at intersections where buses
may interact with other traffic;
alongside design features to
reduce delays caused by
passengers boarding or leaving
buses
BRTS-Bus Rapid Transit System
• Jamie Lerner,1972 –Architect – To
develop a plan for a city that could
accommodate growth but without
congestion and growth.
• Aim: BRT aims to combine the
capacity and speed of a light rail or
metro system (LRT) or heavy rail
with the flexibility, lower cost and
simplicity of a bus system.
• BRTS – Ahmedabad BRTS Janmarg
BRTS-Definitions
Lloyd Wright ITDP (2002)
“ It is a high quality public transport system, oriented to the user that offers fast, comfortable and low cost urban
mobility.”
Levinson et al. (2003)
“ IBRT flexibly combines stations, vehicles, services, running ways, and intelligent transportation system elements
into an integrated system with a strong brand that evokes a unique identity.”
Diaz et al. (2004)
“ BRT has the potential to provide a higher quality
experience that possible with traditional bus operations due
to reduced travel and waiting times, increased service
reliability and improved usability.”
Evolution - BRTS
BRTS-Bus Rapid Transit System
Components - BRTS
Benefits - BRTS
BRTS LITE
Conclusion
