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Protected Permitted Left Turn DisplaysNCHRP 3-54 (02)

Presentation to City of Beaverton Transportation Commission

February 7, 2002

Kent Kacir

Siemens Gardner Transportation Systems

Principal Investigator

Project Manager

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Presentation Outline Background Information

Model 2070 Features

Anticipated Uses/Current Uses

Deployment

Agency’s that have standardized on the Model 2070

Specifications

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Project Objective Project objective: evaluate the safety and

effectiveness of different signal displays used with PPLT control

Determine PPLT usage in the U.S.

Evaluate safety and operational effects

Evaluate drivers’ understanding of various PPLT displays and indications

Evaluate field implementations of selected display(s)

Project deliverables: recommend display(s) for uniform application across the U.S.

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Study Tasks Agency Survey

Static Driver Survey

Operational and Conflict Study

Crash Analysis

Interim Report and Panel Meeting

Animated Driver Survey

Field Study

Panel Meeting and Final Report

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MUTCD and PPLT MUTCD says that a separate traffic signal display for PPLT

control is not required

PPLT Display:

5-section

green arrow protected indication

green ball permitted indication

through movement indication displayed simultaneously with protected indication

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What is the Problem? Some traffic engineers think the green ball permitted display is

problematic

Argue that left-turn drivers may interpret the green ball as a protected indication

At least 4 variations of the permitted indication has been developed

Signal display arrangement and supplemental sign use varies

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Yellow Trap

1

6

5

2

When 1 lags …… 5 gets the yellow trap

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RESEARCH RESULTS

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PPLT Use in the United States

107,219 signalized intersections represented in 168 surveys analyzed

29 % of those intersections use PPLT phasing on at least one approach

IntersectionsWithout PPLT71%

PPLTIntersections29 %

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Use of PPLT by State

5-SECTION CLUSTER5-SECTION VERTICAL4-SECTION VERTICAL3-SECTION VERTICAL5-SECTION HORIZONTAL

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Mounting Location

0%

20%

40%

60%

80%

100%

Per

cent

of

Tot

al

Center overLT Lane

Btwn LT andThru Lane

Other VaryLocation

3 V

4 C

4 V

4 H

5 C

5 V

5 H

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Location of Unique PPLT Indications

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Data Collection Locations

Dallas

College Station

Portland

Seattle Detroit

Dover

Cupertino

Orlando

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Static Survey

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Demographics 2,465 drivers

73,950 scenarios

58 % male - 41 % female

Driver’s age

27 % < 24

44% 24 to 44

21 % 45 to 65

7 % > 65

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Early Conclusions Drivers had better understanding of flashing permitted

indications (less fail critical errors)

No age difference with flashing indications

Drivers over the age of 65:

32 % correct response rate with green ball

Over 63 % correct response rate with flashing indications

2 - 3 seconds additional response time

Response time lower with flashing indications

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Further Study Permitted Indication

The use of flashing permitted indications should be considered in future evaluation

Driver understanding

Fail critical responses

Older driver comprehension

Additional study required

clearance interval - right turns

driving - shared lanes

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Proposed Vertical FYA Display

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UMASS Simulator

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Example of Virtual World

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FIELD IMPLEMENTATION

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FYA Implementation Sites

Implemented

Near Implementation

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Woodburn, Oregon

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Woodburn, Oregon

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ODOT News Release

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Local Press

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Citizen Response

“My opinion is that if the intersection had flashing yellow arrows at the turn-lane, this accident may have been avoided…When I see a green light, my first reaction is “go” so I sometimes find myself responding to that trained response rather than the one that says “don’t go when another car is coming.” Alternatively, when I see a flashing yellow arrow, there is no question that I need to watch what I’m doing, look for approaching vehicles, and turn when it’s safe…”

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What is Required ? Identify 3 intersections that are currently operating with PPLT, and

that have been doing so for 3 years.

Identify 3 intersections to serve as control sites.

Provide background information: Lane widths

Historical crash data

Traffic volumes

Track and report change over costs and implementation issues.

Provide the necessary change over (equipment and man-power).

Submit a Request for Experimentation to Federal Highway Administration

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What Does the NCHRP Contractor Do? Assist Agency in site identification

Provide technical assistance related to controller logic

Provide “form letter” to submit FHWA request

Collect Before and After Conflict data

Analyze field operational data

Analyze field conflict data

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Potential SitesWestern / 5th

Allen / Wilson

Allen / Menlo

125th / Longhorn

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Questions ?Kent Kacir

503-624-7635

Kent.kacir@gts.sea.siemens.com