Development of An Affordable Loop Detector Simulator (LOOPSIM) for In-Laboratory Traffic Research and Training

Patikhom Cheevarunothai, Dr.Yinhai Wang & Dr. Nancy L. Nihan

Presented by Cheevarunothai Patikhom (Num)

University of Washington

Problems and Objectives

Live loop detector inputs may not be available in laboratories where hardware and software need to be tested.

Uncontrollable traffic streams on freeways

High total testing cost

Create a system that can simulate calls from loop detectors without having physical loops in laboratories, to test algorithms executable in the controller or test the performance and accuracy of traffic data collection systems

A Model 332 Cabinet

170 Controller

Input File

Front Side Back Side

Output Signals

12V

Voltage

0V Time

0V = With CarsNote: 12V = W/O Cars

Headway Scan Count

System Connection

Input File ControllerLOOPSIM

12V SignalInput File ControllerBefore

After

System Components

Laptop Computer with a PCMCIA port Digital I/O Card Reed Relay Circuits Cable Connections

Cable Connection

System Architecture

Input File Controller12V

LOOPSIM

System Features

1) Channel Connection Test Check the operation of every channel before

actual tests

2) Vehicle Arrival Pattern Simulations Different distribution of vehicle arrival patterns,

e.g., Uniform, Normal, and Erlang distribution.

3) Roadway Traffic Emulations** Replaying of collected traffic event data

Program User Interface

System Test Setting

LOOPSIM was tested with a Model 332 controller cabinet installed with a Type 170 controller.

Eight double-loop systems (16 channels)

Test Results : Vehicle Arrival Pattern Simulation

Sending Data

050

100150200250300350400450

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Channel Number

SENDC

SENDHW

Receiving Data

050

100150200250300350400450

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Channel Number

RECVC

RECVHW

Scan Count

Scan Count

Comparison of Scan Counts & Headway

Test Results : Roadway Traffic Emulations

Sending Data

0

50

100

150

200

250

300

1 122 243 364 485 606 727 848 969 1090 1211 1332 1453 1574 1695 1816 1937

Time(Millisecond)

SEND1

SEND2

Receiving Data

0

50

100

150

200

250

300

1 88

175

262

349

436

523

610

697

784

871

958

1045

1132

1219

1306

1393

1480

1567

1654

1741

1828

1915

Time(Millisecond)

RECV1

RECV2

Binary Output

Binary Output

Comparison of Binary Outputs

Note : One byte contains the statuses of eight loop detectors at a particular moment.

Advantages

Economical system suitable for in-laboratory traffic system testing (total cost $400)

Easy-to-built system architecture Precise real-time performance at 60 Hz or

higher Capability to control traffic characteristics in

line with the purpose of testing or training Simple to use the replayed data as ground

truth data for evaluating the performance of systems or estimations models

Future works

The feed back function from controller to computer

Add more simulation features Testing with different other types of

controllers and cabinets

Conclusions

LOOPSIM makes live loop inputs available in laboratories for traffic research and training

Test results show that LOOPSIM is reliable and accurate

Affordable system for research institutes and universities