Traffic - Traffic Engineering and Management - Lecture Notes, Study notes for Engineering Project Management. Alagappa University

Engineering Project Management

Description: Some concept of Traffic Engineering and Management are Non-Intrusive Technologies, Non-Transportation Designers, Parametric Description, Pedestrian Crossing. Main points of this lecture are: Traffic, Fundamental Parameters, Traffic Engineering, Economical Operation, Mutual Relationships, Stream Parameters, Traffic Engineer, Planning, Traffic Stream, Whole Traffic
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Traffic Engineering And Management 1. Fundamental Parameters of Traffic Flow
Chapter 1
Fundamental Parameters of Traffic
1.1 Overview
Traffic engineering pertains to the analysis of the behavior of traffic and to design the facilities
for a smooth, safe and economical operation of traffic. Traffic flow, like the flow of water,
has several parameters associated with it. The traffic stream parameters provide information
regarding the nature of traffic flow, which helps the analyst in detecting any variation in flow
characteristics. Understanding traffic behavior requires a thorough knowledge of traffic stream
parameters and their mutual relationships. In this chapter the basic concepts of traffic flow is
1.2 Traffic stream parameters
The traffic stream includes a combination of driver and vehicle behavior. The driver or human
behavior being non-uniform, traffic stream is also non-uniform in nature. It is influenced not
only by the individual characteristics of both vehicle and human but also by the way a group
of such units interacts with each other. Thus a flow of traffic through a street of defined
characteristics will vary both by location and time corresponding to the changes in the human
The traffic engineer, but for the purpose of planning and design, assumes that these changes
are within certain ranges which can be predicted. For example, if the maximum permissible
speed of a highway is 60 kmph, the whole traffic stream can be assumed to move on an average
speed of 40 kmph rather than 100 or 20 kmph.
Thus the traffic stream itself is having some parameters on which the characteristics can
be predicted. The parameters can be mainly classified as : measurements of quantity, which
Dr. Tom V. Mathew, IIT Bombay 1 March 31, 2012
Traffic Engineering And Management 1. Fundamental Parameters of Traffic Flow
includes density and flow of traffic and measurements of quality which includes speed. The
traffic stream parameters can be macroscopic which characterizes the traffic as a whole or
microscopic which studies the behavior of individual vehicle in the stream with respect to each
As far as the macroscopic characteristics are concerned, they can be grouped as measurement
of quantity or quality as described above, i.e. flow, density, and speed. While the microscopic
characteristics include the measures of separation, i.e. the headway or separation between
vehicles which can be either time or space headway. The fundamental stream characteristics
are speed, flow, and density and are discussed below.
1.3 Speed
Speed is considered as a quality measurement of travel as the drivers and passengers will be
concerned more about the speed of the journey than the design aspects of the traffic. It is
defined as the rate of motion in distance per unit of time. Mathematically speed or velocity v
is given by,
where, vis the speed of the vehicle in m/s, dis distance traveled in m in time tseconds. Speed
of different vehicles will vary with respect to time and space. To represent these variation,
several types of speed can be defined. Important among them are spot speed, running speed,
journey speed, time mean speed and space mean speed. These are discussed below.
1.3.1 Spot Speed
Spot speed is the instantaneous speed of a vehicle at a specified location. Spot speed can be
used to design the geometry of road like horizontal and vertical curves, super elevation etc.
Location and size of signs, design of signals, safe speed, and speed zone determination, require
the spot speed data. Accident analysis, road maintenance, and congestion are the modern fields
of traffic engineer, which uses spot speed data as the basic input. Spot speed can be measured
using an endoscope, pressure contact tubes or direct timing procedure or radar speedometer
or by time-lapse photographic methods. It can be determined by speeds extracted from video
images by recording the distance traveling by all vehicles between a particular pair of frames.
Dr. Tom V. Mathew, IIT Bombay 2 March 31, 2012
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