Weather Responsive Traffic Management. Wyoming DOT Variable Speed Limit (VSL) Project. March 2012

Transcription

1 Weather Responsive Traffic Management Wyoming DOT Variable Speed Limit (VSL) Project March 2012

2 I-80 Background Information >50% of I-80 traffic in Wyoming is commercial vehicles Rural AADT 11,000 vehicles per day Peak Elevation along I-80 in Wyoming: 8640 Frequent adverse weather conditions Strong winds Heavy snow Blowing snow Visibility problems Drifting of snow Icy conditions

3 I-80 - Background Information Frequent closures Crash rate is higher than average in the VSL corridors Several multi-vehicle fatalities in the corridors

4 Legislation (WS ) Legislation went into effect 7/1/2008 Grants authority to set the speed limit based on vehicle or weather emergency differing limits may be established for different times of day, different types of vehicles, varying weather conditions, and other factors bearing on safe speeds, which shall be effective when posted upon appropriate fixed or variable signs.

5 I-80 VSLs

6 VSL System SPEED SENSOR VSL SIGN RWIS

7 Sign Technologies

8 VSL Approach Provide timely and site-specific regulatory speed limit to guide travelers through the corridor VSLs located at interchanges to inform people as soon as they enter the system VSL located on both median and shoulder side for visibility

9 VSL Approach Focus: tighten speed distribution

10 Representative Scenario

11 Protocol Cooperation between: Troopers Maintenance TMC Troopers, Maintenance and TMC authorized to adjust the speed limits TMC makes the adjustments and calls out on the radio so everyone is informed

12 Protocol Process takes about a minute or two for TMC to: Receive request for speed reduction Reduce speed at roadside Inform the public (website, phone system, text/ notification) Depending on conditions, speeds could be adjusted every few miles and speeds could be adjusted a few times per hour

13 Absence of Visual Inspection TMC has approval to adjust speeds Use RWIS and Speed Data Based on AASHTO Stopping Sight Distances Building a more detailed algorithm (U.W.)

14 Dry and Clear Storm Begins to Impact Roadway VSL in Effect Storm Clears (VSL In Effect)

15 Representative Scenarios #1 - Patrol Trooper is on I-80 and is working a crash due to icy road conditions Patrol Trooper contacts TMC via radio and requests a speed reduction TMC Operators reduces speed and makes a call out on radio channel scanned by both Patrol and Maintenance TMC then informs the public of the speed reduction (web, phone, text/ )

16 Representative Scenarios #2 Plow Operator identifies visibility issue of less than 500 feet Plow operator contacts TMC and asks for pace speed Plow operator requests a speed reduction TMC Operators reduces speed and makes a call out on radio channel TMC then informs the public of the speed reduction (web, phone, text/ )

17 Representative Scenarios #3 Neither Patrol or Maintenance is available and sensors indicate visibility <600 with dry pavement (fog) TMC Lead Operator is authorized to reduce speed TMC makes a call out on radio channel scanned by both Patrol and Maintenance TMC then informs the public of the speed reduction (web, phone, text/ )

18 Issues One section of VSL seems to result in more issues than others Speeds are not raised as soon as they should be It is one of our newest sections Some people are reluctant to request speed changes Cooperation between Patrol, Maintenance and TMC is critical - Everyone must participate Recent meeting should resolve ownership issue

19 Issues Amber vs. White LEDs vs. Static Black on White Condition Sign Legibility Distance Morning/Fog Static Speed Limit 400 ft Amber VSL 830 ft White VSL 615 ft Dry/Clear/Sunny Static Speed Limit 470 ft Amber VSL 1530 ft White VSL 1115 ft Dark/Clear Static Speed Limit 400 ft Amber VSL 420 ft White VSL 700 ft

20 Questions/Comments?