Everyday Mapping of Traffic Conditions An Urban Planning Tool

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Everyday Mapping of Traffic Conditions - An
Urban Planning Tool
Prof. P. Savvaidis - Ass. Prof. I. Ifadis - Dr.
K. Lakakis

• Laboratory of Geodesy
• Aristotle University of Thessaloniki,
• Department of Civil Engineering

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• A major problem in designing a traffic plan
• for an urban area
• The availability of traffic data and the cost in
  time and money of their updating

• The traffic conditions are characterized or can
  be simulated by
• Mean vehicle speed
• Traffic volume, traffic density
• Traffic capacity etc.

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Traditional ways of obtaining traffic data

• Observations carried out at certain points
• Movement of a vehicle along traffic routes
• Use of recording instrumentation

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These conventional techniques are

• Simple in practice
• Time consuming
• Need a large number of observers to cover a
  road network
• Provide data only for the period of the
  measurements
• Updating the observed data in a future occasion
  requires the organization of a new survey
• The results will again soon be out of date

BUT
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To overcome these problems
A land navigation system was developed in the
Laboratory of Geodesy, School of Civil Engineering
The system was used in a pilot project as the
mean for the determination of the basic traffic
parameters in the downtown part of the city of
Thessaloniki.
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Vecon (VEhicle COntrol and Navigation System)
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Vecon Framework
VEHICLES
CONTROL STATION
Continuous GPS Reference Station
Controlled Moving Units
Telecommunication System (UHF)

• GPS antenna
• GPS receiver
• Prime Unit of GPS
• Differential Corrections

• GPS antenna
• GPS receiver
• RTCM ready

(RTCM format)
(RTCM format)

• Antennas
• Transceivers
• Modems

(???? format)

• Spatial and Time Digital Maps (x,y,t)
• Regression, Exponential smoothing,
  Autoregression, Adaptive Filters, etc.
• Graph Algorithms.
• Shortest path, Best delivery route, etc.
• User Interface

(???? format)
USER
GIS Unit
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Continuous GPS Reference Station
GIS Unit
VeconControl Station
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VeconControl Station
Telecommunication System (UHF)
VeconVehicle Unit or Sensor
The Vehicle Unit
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How Vecon works

• When incorporating the system for the first
  time, the GPS/GIS operations are based on
  available existing digital maps of the area of
  interest
• The system computes and displays a new digital
  map of the area under investigation with the
  accuracy of the DGPS
• Depending on the number of vehicle sensors and
  their travelling along the urban road network,
  the system gradually builds its own map in a
  continuous and self-feeded way

It builds the digital map
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How Vecon works

• GPS is a very accurate timekeeper with spatial
  reference
• The GPS module of the system provides
  continuous recording of time data
• The obtained vehicle positions always refer to
  specific times easily found in the resulting
  files
• By using the appropriate software, the time
  needed for each vehicle sensor to travel between
  two nodes of the road network can be computed

It measures travel times
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Computation of traffic data

• For each segment, the travel time between the
  starting and the ending node is computed from the
  GPS time data.
• Knowing the distance between the nodes and the
  respective travel time, the speed of the vehicle
  along the particular road segment is computed.

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Computation of traffic data

• Traffic volume Q (vehicles/hour) can be related
  to mean vehicle speed V both theoretically and
  empirically (e.g. by using the equations proposed
  by Greenshields or by Greenberg)
• Traffic density K (vehicles/km or mile) can be
  also computed from empirical equations giving the
  value of K as a function of the mean vehicle
  speed V (e.g. the Greenberg equation)

Q 122 V 1.65 V2

  Q
227 V e V/17.2
Q 74 K 0.61 K2
K 227 e 0.0581 V

 
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Possible Vecon Vehicle Sensors

• Single Vehicle Sensor
• Small Fleet of Vehicle Sensors travelling along
  the road network of an urban area according to a
  pre-determined plan
• Vehicle Fleet Systems already operational
• Urban transportation units buses
• Taxi fleets

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Possible Vecon Vehicle Sensors

• Urban transportation units will give
  information along
• main roads
• Taxi vehicles will cover the main and secondary
  
• roads in a random way
• Taxi vehicles can very soon gather a lot of
  data all during
• the day
• The time database of the system will be
  continually
• enriched, thus updating the available
  traffic data on an
• everyday basis

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Conclusions
The Vecon System

• functions as a self-governed closed system
  because it can produce the needed digital
  geographical database from its incoming
  information
• records travel times with the help of the GPS
  system for every road segment driven through by
  each vehicle sensor, thus providing a digital
  time database from which traffic parameters can
  be also computed
• can make use of existing vehicle fleets in an
  urban area, rapidly collecting data and covering
  the whole road network in the simplest way
• can be defined as a dynamic system because,
  during the everyday operation, it continuously
  updates and corrects its databases, optimizing in
  this way their effectiveness
• can be used for real time monitoring of traffic
  conditions under disaster or emergency situations
  when all the previously available data become
  invalid or unreliable