Advances in Inductive Loop Detectors for Stop Bar Detection and Counting

1. Advances in Inductive Loop Detectors for Stop Bar Detection and Counting Scott Evans VP of Engineering Eberle Design Inc Detection SystemsITS America Annual Meeting & ExpoJune 6, 2007, Palm Springs CA 050807

2. Evolution • Invented in Mid 50’s… yes the “1950’s”. • Engineering Standards beginning in the early 80’s until present. • 80’s & 90’s saw major developments in electronics, geometrics, and installation standards.

3. Evolution • Mid 90’s to present day, loop detection is reliable, accurate, simple to engineer and install, and conforms to standards. • Many new capabilities over generally understood simple detection have become available. • Loops are an invasive technique and do require maintenance.

4. What is new? • New enhanced digital electronic designs leading to very high reliability and near faultless performance • Robust – less reliance on loop quality • Diagnostics for simple field installation & troubleshooting • Advanced Count Algorithms • Loop detection works in poor weather and poor lighting conditions

5. Sophisticated Capabilities • Advanced capabilities • LCD Graphical Menu Driven User Interface • Built in tools to aid in correct setup • Advanced uP based algorithms with higher operating and sampling speeds • Automatic environmental tracking • Fewer components for reliability • Properly configured modern loop detectors can provide exceptional operation even when presented with adverse conditions or poorly maintained loop systems.

6. Sophisticated Capabilities • Built-in tools for simple installation & trouble shooting • Call Strength meter • Frequency meter • Frequency stability meter • Fault Monitoring • Detect and report loop issues such as open, shorted, and large change in inductance • Communications • NTCIP TSS Object MIB • Vehicle classification and identification via Signature analysis • Built-in Applications • Speed Trap • Directional Logic • 3rd Car Logic

7. The Need For Traffic Data • The NTOC recently published National Traffic Signal Report Card gave an overall grade of D- with detection getting an F. • Cycle by cycle data has been shown to be an effective method of analyzing a signalized intersection with Measures of Effectiveness such as volume to capacity ratios, arrival type, and average vehicular delay. • Traffic counts form the basis of almost all work performed by transportation engineers and planners.

8. Vehicle Counting at the Stop Bar • Good traffic data is used in allocation of federal transportation funds, used in planning and design of the transportation system, used in financial and tax assessment, and used in environmental assessment. • Traffic data at signalized intersections are used in a variety of planning and traffic operational analyses: site impact studies, level of service analysis, intersection design studies, signal retiming, etc. • The potential to extract traffic counts from existing signalized intersection loop detection provides a golden opportunity.

9. Loop Detector Count Capabilities • What is a Counting Detector? • A primary output provides the traditional presence output indicating the detection zone is occupied. • A secondary output of the detector provides a pulse for each vehicle entering the detection zone. • Many loop configurations are supported, for example: • Single small loop (6 ft length) • Single long loop (12 to 50 ft length) • Multiple small loops in series (two to eight 6 ft)

10. Loop Detector Stop Bar Counting • Recent INDOT field studies of the EDI Oracle Loop Monitor have demonstrated “truthed” loop detection errors less than 1%.

11. Loop Detector Stop Bar Counting • Shorter 15 minute bins reveal +/- 4% errors on raw count data due primarily to lane violations.

12. Stop Bar Counting Analysis • Poor lane discipline by drivers contributed far more overall error than actual detector issues. • Thus, lane design and loop placement become the primary factors when using modern counting style loop detectors, but very high accuracies can be obtained 24 hours a day, in good or bad weather.

13. Loop Detector Stop Bar Counting • New Adaptive control algorithms depend on accurate and real-time vehicle data input. • 365 days per year of data collection. • Many agencies develop and deploy advanced techniques to improve traffic flow…But suffer from a reliable method to gauge their effectiveness.

14. In Summary • Sixty years of development has led to long term reliability, low cost, and precise results. • Developing traffic data from existing loop infrastructure is a golden opportunity. Inductive Loops… Still the benchmark to which all others are measured against.

15. References • ITE Traffic Engineering Council • TENC 103-02 Using Existing Loops at Signalized Intersections for Counts • TRB Paper 06-1143, 11/1/2005 • Evaluation of Flow Based Traffic Signal Control Using Advanced Detection Concepts • ITE Traffic Detector Handbook • 2nd Edition, 1997

16. Thank You • Some examples of advanced loop detectors with counting capability: www.EDItraffic.com