I- 80 PARLEYS CANYON VARIABLE SPEED LIMIT North/West Passage - - PowerPoint PPT Presentation

I-80 PARLEY’S CANYON VARIABLE SPEED LIMIT

North/West Passage Virtual Scanning Tour August 19, 2015

Glenn Blackwelder– UDOT Traffic Operations Center

Introduction

• 1. History
• 2. Laying the Groundwork
• 3. Design Process
• 4. Operations
• 5. Results

I-80 Parley’s Canyon Feasibility Study 2011

• Rural 6-lane freeway east of Salt Lake City
• Mountainous terrain (steep grades, winding

geometry)

• Speed limit 65 mph

I-80 Parley’s Canyon Feasibility Study 2011

Severity Dry Wet Snow Slush Ice Water T

• tal

% 1 280 116 84 49 28 6 565 77% 2 43 19 10 4 8 2 86 12% 3 25 16 4 2 5 1 53 7% 4 15 5 1 1 22 3% 5 2 2 4 1% T

• tal

365 158 98 56 42 9 730 100% % 50% 22% 13% 8% 6% 1%

Crash Analysis

I-80 Parley’s Canyon Feasibility Study 2011

Mile Post (MP) Total Vehicles Involved in Crashes Angle Crashes Rear End Crashes Head On Crashes Sideswipe Crashes Single Vehicle Crashes Crashes NOT

• n a Clear

Day Collision w/ Wild Animal from to 136.00 136.09 15 2 2 1 8 10 136.10 136.19 16 2 1 1 1 10 9 1 136.20 136.29 10 1 1 8 6 136.30 136.39 4 1 1 2 2 1 136.40 136.49 8 1 2 5 2 2 136.50 136.59 6 2 2 2 3 136.60 136.69 5 1 1 3 2 136.70 136.79 3 1 1 1 2 136.80 136.89 7 1 3 3 3 2 136.90 136.99 14 1 1 2 10 6 4 137.00 137.09 14 2 4 2 6 8 2 137.10 137.19 23 2 5 3 13 11 4 137.20 137.29 16 4 11 8 4 137.30 137.39 6 3 1 2 3 1 137.40 137.49 9 1 2 6 4 1 137.50 137.59 16 5 1 4 6 4 3 137.60 137.69 7 1 1 5 1 137.70 137.79 5 2 1 2 3 137.80 137.89 6 1 2 3 2 137.90 138.00 16 1 3 1 4 7 5 2 Totals: 206 10 42 6 31 113 88 33

CONFIDENTIAL: Protected under 23 USC 409

Laying the Groundwork

• Guidelines for VSL was being developed by

FHWA (not released yet)

• UDOT developed process
• Type of VSL Sign
• Locations
• Operations

Design Process

VSL Types

Advisory Speed vs. Regulatory Speed Full matrix vs. Hybrid Solar vs. hard-wired

Design Process

VSL Types

Advisory Speed vs. Regulatory Speed Full matrix vs. Hybrid Solar vs. hard-wired Wireless vs. fiber-backed

Design Process

• VSL signs would be regulatory (enforceable)
• Hybrid

VSL signs

• Utilize existing ATMS infrastructure for power and

communications

• CCTV Infrastructure for verification

Design Process

DevelopVSL sign location criteria

• 1. On-Ramp Merges
• 2. Terrain
• 3. Confirmation

4500 5000 5500 6000 6500 7000 127128129130131132133134135136137138139140141142143144145 Elevation Milepost

Parley's Canyon Elevation Profile

E

MP New/Rep Camera Visibility Distance to Next Sign (mi) Location Criteria Interchange Terrain Confirmation 128 New 0.8 X X 128.8 Replace 1.9 X 130.7 New 1.6 X 132.3 New 2.2 X X 134.5 New 2.1 X X 136.6 Replace 2.7 X X 139.3 New 1.0 X 140.3 Replace N/A X X

Design Process

Sign locations - Eastbound

• Good Visibility
• Fair Visibility
• No Visibility

MP New/Rep Camera Visibility Distance to Next Sign (mi) Location Criteria Interchange Terrain Confirmation 141.0 Replace 2.4 X X 138.6 New 1.8 X X 136.8 New 1.8 X X 135.0 New 1.8 X X 133.2 New 1.8 X 131.4 Replace 1.8 X 129.5 Replace N/A X X

Design Process

Sign locations -Westbound

• Good Visibility
• Fair Visibility
• No Visibility

PROJECT COST SUMMARY

$700,000 Project Cost ($40k/sign) Sign costs are a fraction of the total cost Power and comm influence the cost significantly

Integration Steps

• Sign procurement – New vendor contract.
• Lab Testing of sign and communications plan.
• Integration into TransSuite – new device driver.
• Decision support software.

Sign Testing at Transcore Lab

Basis for Developing the Process

• f VSL Operations

Speed Change based on Utah Basic Speed Law – Prima Facie Speed characteristics....85th percentile of drivers represent reasonable and prudent speed under prevailing conditions. We are not setting the ‘Safe’ Speed...We are setting it based on reasonable and prudent driver behavior.

Speed Change Operations Considerations

Changing the Speed

• Two Parts
• Engineering & Policy
• Region Traffic Operations Engineer
• Traffic Engineer Order – UDOT process for traffic regulations
• Mechanical
• Operator in the Control Room can make the change as

directed by the TOE & TEO

• The TOE can use the Decision Support Software

Actually changing the Speed Limit

UDOT developed a custom interface

Software Process

The software creates a record of speed limit decisions in a weather event. An event is triggered when it is requested by UDOT or UHP staff.

Starting the Process

When an event is requested, the TOC operators contact an engineer who will run the event.

Gathering Information

At the start of the event, the weather group at the TOC does a short-term forecast, and freshens it at 1-3 hour intervals.

Setting the Speed Limit

The traffic engineer reviews the weather forecast, notes from the operators and then goes to this page The graphs show speeds

• n I-80. Lane 1 is

approximately the 85th percentile speed.

The Speed Decision

Factors in Speed Choice

• 85th Percentile Speed
• Expected weather trend (better, worse or the

same)

• Shed Feedback (will road be clear soon?)
• Chain Restrictions
• End result – an engineering study

Implementing the Limit

Steps to Finalize Speed Limit

• Engineer enters selected speed and reason
• Signs change
• Automatic email to UDOT and UHP
• The TOC operators notify dispatch

(start of event only)

• TOC operators post on overhead VMS

Photo: Chris Siavrakas

End of the Event

A VSL event ends when the speed returns to free- flow (above 65 mph in left lane) and there is no further weather expected.

Photo: UDOT

Operation Results

• First event on January 6, 2014
• 78 events through July 31, 2015.
• During those events, engineers

evaluated speed limits 391 times

• Note –The system was also active

about 70 times for construction and several times for testing

Weather ops

Weather ops

Reactions - Anecdotal Evidence

• Positive feedback from public and agencies
• The main complaint has been the brightness (or lack

thereof) of the signs (which has been addressed)

• Repositioning photocell
• Sign tilt to adjust for grade
• Added black border on outside of module

Operational Changes

• Missed a few opportunities to lower the speed

limit – we’ve asked our TOC operators, UHP and weather staff to be more aggressive on starting events

• The engineers responsible would like to consider

automation.

UDOT Stats

UDOT does not have a sufficient data to assess the effects of VSL on crashes.

• Would like to see a 3-5 year baseline
• VSL runs a limited number of hours per winter
• Weather severity is a big factor – and that changes from

year to year

Items to consider when implementing VSL

• Operational Costs/Opportunity Costs
• Maintenance and Redundancy

Operational Costs/Opportunity Costs

• Fine tuning of system after deployment
• Regulatory Signs prioritized over Warning Signs
• Approximately 1 FTE additional workload
• ¼ time Engineer
• ¼ time Operator/Weather Forecast
• ½ time Maintenance (Hardware/Software)

Maintenance and Redundancy

• Regulatory Signs prioritized over Warning Signs
• Power and Communication Failures – What to

do?

• Send crews out in storm?
• How many blank signs are acceptable?

Thank You!