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 Crash Analysis Severity Dry Wet Snow Slush Ice Water T otal % 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 0 1 1 0 22 3% 5 2 2 0 0 0 0 4 1% T otal 365 158 98 56 42 9 730 100% % 50% 22% 13% 8% 6% 1%
I- 80 Parley’s Canyon Feasibility Study 2011 Mile Post (MP) Total Vehicles Crashes NOT Involved in Rear End Head On Sideswipe Single Vehicle on a Clear Collision w/ from to Crashes Angle Crashes Crashes Crashes Crashes Crashes Day Wild Animal 136.00 136.09 15 2 2 0 1 8 10 0 136.10 136.19 16 2 1 1 1 10 9 1 136.20 136.29 10 0 1 1 0 8 0 6 136.30 136.39 4 0 0 1 1 2 2 1 136.40 136.49 8 0 1 0 2 5 2 2 136.50 136.59 6 0 2 0 2 2 3 0 136.60 136.69 5 0 1 0 1 3 2 0 136.70 136.79 3 0 1 0 1 1 2 0 136.80 136.89 7 1 3 0 0 3 3 2 136.90 136.99 14 0 1 1 2 10 6 4 137.00 137.09 14 2 4 0 2 6 8 2 137.10 137.19 23 2 5 0 3 13 11 4 137.20 137.29 16 0 4 0 0 11 8 4 137.30 137.39 6 0 3 0 1 2 3 1 137.40 137.49 9 0 1 0 2 6 4 1 137.50 137.59 16 0 5 1 4 6 4 3 137.60 137.69 7 0 1 0 1 5 1 0 137.70 137.79 5 0 2 0 1 2 3 0 137.80 137.89 6 0 1 0 2 3 2 0 137.90 138.00 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 Parley's Canyon Elevation Profile 3. Confirmation 7000 6500 Elevation 6000 5500 5000 4500 127128129130131132133134135136137138139140141142143144145 Milepost E
Design Process Sign locations - Eastbound Location Criteria Distance to Next MP New/Rep Camera Visibility Sign (mi) 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 -Good Visibility -Fair Visibility -No Visibility
Design Process Sign locations -Westbound Location Criteria Distance to Next MP New/Rep Camera Visibility Sign (mi) 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 -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 of VSL Operations Speed Change based on Utah Basic Speed Law – Prima Facie Speed characteristics....85 th 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 on I-80. Lane 1 is approximately the 85 th percentile speed.
The Speed Decision Factors in Speed Choice 85 th 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!
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