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TRAFFIC Notes of AM Fillone, DLSU-Manila

TRAFFIC ENGINEERING

Introduction

Traffic engineeringis defined by the Institute of Transportation Engineers (ITE) as the

application of technology and scientific principles to the planning, functional design,operation, and management of facilities for any mode of transportation in order to

provide for the safe, rapid, comfortable, convenient, economical, and environmentally

compatible movement of people and goods.

Traffic engineeringis concerned with

the safety of the public,

the efficient use of transportation resources, and

the mobility of people and goods

Traffic flow characteristics include time headway, flow, time-space projectory, speed,distance headway, and density.

Traffic flow analytical techniquesinclude supply-demand modeling, capacity and level-of-service analysis, traffic stream modeling, shoc wave analysis, !ueueing analysis, and

simulation modeling.

Transportation engineers and system planners, designers, and operators should have a

basic nowledge of traffic flow fundamentals.

Engineers and planners assess traffic and environmental impacts of proposed system

modifications, and this can be accomplished only through a supple-demand frameworthat re!uires understanding of flow characteristics and their interrelations.

Table "." E#amples of $odal Traffic %perations

Transport $ode $icroscopic $acroscopic

&ir &irways, airfields, gate positions

(aircraft)

Terminals, chec-in, gate

positions (persons)

'ater ort facilities, line-haul operations,

locs (ship)

Terminals (freight)

ail *rban systems, railroads (trains) Terminals (persons)

+ighway Intersections, trucs and grades

(vehicles)

oute operations, paring

(vehicles)%ther edestrians, elevators (persons) edestrians, escalators,

conveyor belts (persons or

freight)

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TRAFFIC Notes of AM Fillone, DLSU-Manila

An Analytical Approach

The analytical process consists of predicting an output as a function of specified

inputs.

This analytical process can vary from a simple e!uation to a comple# simulation

model. & flowchart is shown in igure "." to illustrate this analytical process and to

emphasie the importance of nowing fundamental flow characteristics and basic

analytical techni!ues.

Traffic characteristics

The fundamental characteristics of traffic flow are flow, speed, and density

Table "./ provides a framewor for these characteristics

Table "./ ramewor for undamental 0haracteristics of Traffic low

Traffic 0haracteristics $icroscopic

(Individual *nits)

$acroscopic (1roups of

*nits)

low Time headways low rates

2peed Individual speeds &verage speeds

3ensity 3istance headways 3ensity rates

Trafficdemand

TransportSupply

Trafficcontrol

Characteristicsand Analysis

TrafficPerformance

Figure 1.1 The Analytical Process

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TRAFFIC Notes of AM Fillone, DLSU-Manila

TRAFFIC STREAM ARAMETERS

Two broad categories4

". macroscopic parameters5 characterie the traffic stream as a whole

/. microscopic parameters5characterie the behavior of individual vehicles in thetraffic stream with respect to each other

& traffic stream may be described macroscopically by three parameters4

". 6olume or rate of flow

/. 2peed

7. 3ensity

!olu"e# flow and density relationships

The following figures " to 7 describes the traffic volume, flow and density relationsships4

$ean speed,

v

3ensity, (veh8m)

$ean speed,

v

low ! (veh8hr)

low, !

3ensity (veh8m)