Traffic Engineering.

1. Traffic Engineering
Traffic engineering is that phase of transportation
engineering which deals with the
planning,
geometric design and
traffic operations
of roads, streets, and highways, their networks,
terminals, abutting lands, and relationships with
other modes of transportation.
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Safety: The Primary Objective
The principal goal of the traffic engineer
remains the provision of a safe system for
highway traffic.
Other Objectives of Traffic Engineer
• Speed
• Comfort
• Convenience
• Economy
• Environmental compatibility

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•While SPEED of travel is much to be desired, it is limited by
transportation technology, human characteristics, and the need
to provide safety.
•COMFORT and CONVENIENCE are generic terms and mean
different things to different people.
•Comfort involves the physical characteristics of vehicles and
roadways, and is influenced by our perception of safety.
•Convenience relates more to the ease with which trips are
made and the ability of transport systems to accommodate all
of our travel needs at appropriate times.

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• ECONOMY is also relative.
Highway and other transportation systems involve massive
construction, maintenance, and operating expenditures, most of
which are provided through general and user taxes and fees.
Nevertheless, every engineer, regardless of discipline, is called
upon to provide the best possible systems for the money.
•HARMONY WITH THE ENVIRONMENT is a complex issue
that has become more important over time. All transportation
systems have some negative impacts on the environment. All
produce air and noise pollution in some forms, and all utilize
valuable land resources.

5. Traffic Engineering Studies

6. Main Categories of Traffic
Studies
 INVENTORIES-provides a list or graphic display
of existing information such as street widths,
parking spaces, transit routes, traffic regulations.
 ADMINISTRATIVE STUDIES-Use existing
records, available in government agencies and
departments.
 DYNAMIC STUDIES- Involves to collect the data
and include studies of speed, traffic volume,
travel time and delay, parking and crashes.

7. Spot Speed Studies
 Location for Spot Speed Studies
 Time of Day and Duration of Spot Speed Studies
 Sample Size for Spot Speed Studies
 Methods for Conducting Spot Studies
 Presentation and Analysis of Spot Speed Data

8. Volume Studies
 Average Annual Daily Traffic (AADT)
 Average Daily Traffic(ADT)
 Peak Hour Volume (PHV)
 Vehicle Classification (VC)
 Vehicle Miles of Travel (VMT)

9. Average Annual Daily Traffic (AADT)
AADT is the average of 24-hour counts collected every day
of the year. AADTs are used in several traffic and
transportation analyses for:
(a) Estimation of highway user revenues
(b) Computation of crash rates in terms of number of crashes
per 100 million vehicle miles.
(c) Establishment of traffic volume trends
(d) Evaluation of the economic feasibility of highway projects
(e) Development freeway and major arterial street systems
(f) Development of improvement and maintenance programs

10. Average Daily Traffic(ADT)
ADT is the average of 24-hour counts collected over a number
of days greater than one but less than a year. ADTs may be
used for:
(a) Planning for highway activities
(b) Measurement of current demand
(c) Evaluation of existing traffic flow

11. Peak Hour Volume (PHV)
PHV is the maximum number of vehicles that pass a point on a
highway during a period of 60 consecutive minute. PHVs are
used for:
(a) Functional classification of highways
(b) Design of geometric characteristics of a highway, for example,
number of lanes, intersection signalization, or channelization
(c) Capacity analysis
(d) Development of programs related to traffic operations for
example, one-way street systems of traffic routing
(e) Development of parking regulations

12. Definitions
 Count – number of vehicles/travelers
passing a highway spot in a counting
period
 Volume – number of vehicles/travelers
passing a highway spot per unit time
 Capacity – maximum and repeatable
volume of vehicles/travelers
 Demand – volume not influenced by
highway capacity

13. Demand
Capacity
Volume
Congestion
Time
Traffic
Intensity

14. Types of Volume Counts
 Cordon Counts
 Screen Line Counts
 Intersection Counts
 Pedestrian Volume Counts
 Periodic Volume Counts
 Continuous Counts
 Control Counts
 Coverage Counts

15. Traffic Volume Data
Presentation
 Traffic Flow Maps
 Intersection Summary Sheets
 Time-Based Distribution Charts
 Summary Tables

16. Travel Time and Delay
Studies
A travel time study determines the amount of time
required to travel from one point to another on a
given route.
In conducting such a study, information may also be
collected on the locations, durations and causes of
delays is known as travel time and delay studies.