Best Practices for
Road Weather
Management
Version 2.0
Prepared
by
Lynette
C. Goodwin
Sr.
Transportation Engineer
Mitretek
Systems, Inc.
for
Paul
Pisano, Team Leader
Road
Weather Management Program
Office
of Transportation Operations
Federal
Highway Administration
May
2003
Table of Contents
Alabama
DOT Low Visibility Warning System
California
DOT Motorist Warning System
City
of Palo Alto, California Flood Warning System
City
of Aurora, Colorado Maintenance Vehicle Management System
Florida
DOT Motorist Warning System
City
of Clearwater, Florida Weather-Related Signal Timing
Idaho
DOT Anti-Icing/Deicing Operations
Idaho
DOT Motorist Warning System
Michigan
Maintenance Vehicle Management System.. 22
Minnesota
DOT Anti-Icing/Deicing System
Montana
DOT Anti-Icing/Deicing Operations
Montana
DOT High Wind Warning System
Nebraska
Road Weather Information for Travelers. 37
Nevada
DOT High Wind Warning System
New
Jersey Turnpike Authority Speed Management
City
of New York, New York Anti-Icing/Deicing System
City
of Charlotte, North Carolina Weather-Related Signal Timing
Oklahoma
Environmental Monitoring System
South
Carolina Hurricane Evacuation Operations
South
Carolina DOT Low Visibility Warning System
Tennessee
Low Visibility Warning System
City
of Dallas, Texas Flood Warning System.. 61
Houston,
Texas Environmental Monitoring System.. 64
Utah
DOT Fog Dispersal Operations
Utah
DOT Low Visibility Warning System
Virginia
DOT Weather-Related Incident Detection. 70
Washington
State DOT Road Weather Information for Travelers
Washington
State DOT Speed Management
Wyoming
DOT Avalanche Warning System
List of Appendices
Environmental
Sensor Technologies
List of
Figures
Figure 1 California DOT Environmental Sensor Station
Figure 2 City of Palo Alto, CA “Creek Level Monitor” Web Page
Figure 3 City of Aurora, CO In-Vehicle Device. 9
Figure 4 Florida DOT Pavement Sensor
Figure 5 City of Clearwater, FL Map
Figure 6A Idaho DOT Maintenance Vehicles
Figure 6B Idaho DOT Chemical Storage Tanks
Figure 7 Idaho DOT Visibility Sensor
Figure 8 Michigan Maintenance Vehicle
Figure 9 Minnesota DOT Ramp Gates and Warning Signs
Figure 10 Minnesota DOT Bridge Anti-Icing System Components
Figure 11 Montana Freeway with Snow-Covered and Dry Pavement
Figure 12 Montana DOT High Wind Warning System Location
Figure 13 Nebraska 511 Road Sign
Figure 14 Nebraska Textual Road Weather Report
Figure 15 Nevada DOT High Wind Warning on DMS
Figure 16 City of New York, NY Anti-icing/Deicing System Operational
Sequence
Figure 17A City of New York, NY Bridge Section Treated with
Anti-icing/Deicing System
Figure 17B City of New York, NY Bridge Section Treated with Truck-Mounted
Sprayer
Figure 18 Oklahoma Environmental Monitoring System Map
Figure 19 South Carolina DOT Contraflow Operations
Figure 20 Tennessee Variable Speed Limit Sign
Figure 21 Tennessee Ramp Gate
Figure 22 City of Dallas, TX Flood Warning System Sign Assembly
Figure 23A Houston Texas Water Level Gauge
Figure 23B Houston Texas Static Warning Sign
Figure 24 Utah DOT Maintenance Vehicle with Fog Dispersal Equipment
Figure 25 Washington State DOT Route-Specific Road Weather Information
Display
Figure 26 Washington State DOT Video of Selected Route with Vehicle
Restrictions
Figure 27 Washington State DOT Reduced Speed Limit on DMS
Figure 28 Wyoming DOT Avalanche Warning System Location
List of Figures (continued)
Figure 29 ESS Operational Applications
Figure 30 Wind Vane
Figure 31 Propeller Anemometer
Figure 32 Cup Anemometer
Figure 33 Sonic Anemometer
Figure 34 Heated Tipping Bucket Rain Gauge
Figure 35 Visibility Sensor
Figure 36 Pavement Sensor
Figure 37 Stilling Well
Figure 38 Friction Meter Mounted on Snowplow
Figure 37 Freeze Point Temperature Sensor
List of
Tables
Table 1 Alabama DOT Low Visibility Warning System Strategies
Table 2 California DOT Motorist Warning System Messages
Table 3 Idaho DOT Winter Maintenance Performance Measures
Table 4 Minnesota DOT Access Control and Maintenance Costs
Table 5 Montana DOT Winter Maintenance Performance Measures
Table 6 Nevada DOT High Wind Warning System Messages
Table 7 South Carolina DOT Low Visibility Warning System Strategies
Table 8 Tennessee Low Visibility Warning System Strategies
Table 9 Utah DOT Low Visibility Warning System Messages
Table 10 Washington State DOT Speed Management Control Strategies
Table 11 Weather Impacts on Roads, Traffic and Operational Decisions
Weather threatens surface transportation nationwide and
impacts roadway safety, mobility, and productivity. Weather affects roadway safety through increased crash risk, as
well as exposure to weather-related hazards.
Weather impacts roadway mobility by increasing travel time delay,
reducing traffic volumes and speeds, increasing speed variance (i.e., a measure
of speed uniformity), and decreasing roadway capacity (i.e., maximum rate at
which vehicles can travel). Weather events influence productivity by disrupting
access to road networks, and increasing road operating and maintenance costs.
There is a perception that transportation managers can do
little about weather. However, three
types of road weather management strategies may be employed in response to
environmental threats: advisory, control, and treatment Strategies. Advisory strategies provide information on
prevailing and predicted conditions to both transportation managers and
motorists. Control strategies alter the
state of roadway devices to permit or restrict traffic flow and regulate
roadway capacity. Treatment strategies supply resources to roadways to minimize
or eliminate weather impacts. Many
treatment strategies involve coordination of traffic, maintenance, and
emergency management agencies. These mitigation
strategies are employed in response to various weather threats including fog,
high winds, snow, rain, ice, flooding, tornadoes, hurricanes, and
avalanches.
This report contains 30 case studies of systems in 21 states that improve roadway operations under inclement weather conditions. Each case study has six sections including a general description of the system, system components, operational procedures, resulting transportation outcomes, implementation issues, as well as contact information and references.
Appendix A presents an overview of environmental sensor
technologies. Appendix B is an acronym
list. Appendix C contains online
resources, including 39 statewide road condition web sites. In Appendix D hundreds of road weather
publication titles, abstracts and sources are tabulated.
In March 1995 a fog-related crash involving 193 vehicles
occurred on the seven-mile (11.3-kilometer) Bay Bridge on Interstate 10. This crash prompted the Alabama Department
of Transportation (DOT) to deploy a low visibility warning system. The warning system was integrated with a
tunnel management system near Mobile, Alabama.
System
Components: Six sensors with
forward-scatter technology are used to measure visibility distance. The visibility sensors are installed at
roughly one-mile (1.6-kilometer) intervals along the bridge. Traffic flow is monitored with a Closed
Circuit Television (CCTV) surveillance system. Video from 25 CCTV cameras is displayed on monitors in the
tunnel control room. Field sensor data
are transmitted to a central computer in the control room via a fiber optic
cable communication system. The
computer controls 24 Variable Speed Limit (VSL) signs and five Dynamic Message
Signs (DMS), which are used to display advisories or regulations to motorists.
System
Operations: Two system
operators staff the tunnel control room 24 hours a day. When fog is observed via CCTV operators
consult the central computer, which displays visibility sensor measurements by
zone. The warning system is divided
into six zones which can operate independently. Depending on visibility conditions in each zone, operators may
display messages on DMS and alter speed limits with VSL signs (as shown in
Table 1).
Table 1 – Alabama DOT Low Visibility Warning System
Strategies
|
Visibility
Distance |
Advisories
on DMS |
Other
Strategies |
|
Less than
900 feet (274.3 meters) |
“FOG
WARNING” |
Speed limit at 65 mph (104.5 kph) |
|
Less than
660 feet (201.2 meters) |
“FOG”
alternating with “SLOW, USE LOW BEAMS” |
·
“55 MPH” (88.4 kph)
on VSL signs ·
“TRUCKS KEEP RIGHT”
on DMS |
|
Less than
450 feet (137.2 meters) |
“FOG”
alternating with “SLOW, USE LOW BEAMS” |
· “45 MPH”
(72.4 kph) on VSL signs · “TRUCKS KEEP
RIGHT” on DMS |
|
Less than
280 feet (85.3 meters) |
“DENSE FOG”
alternating with “SLOW, USE LOW BEAMS” |
· “35 MPH”
(56.3 kph) on VSL signs · “TRUCKS KEEP
RIGHT” on DMS · Street
lighting extinguished |
|
Less than
175 feet (53.3 meters) |
I-10 CLOSED,
KEEP RIGHT, EXIT ½ MILE |
Road Closure by Highway Patrol |
When the speed limit is reduced, notices are automatically
faxed to the DOT Division Office, the Highway Patrol, and local law enforcement
agencies in Mobile and neighboring jurisdictions (i.e., Daphne and Spanish
Ford). If necessary, system operators
request that the Highway Patrol utilize vehicle guidance to further reduce
traffic speeds. During vehicle guidance operations a patrol vehicle with flashing
lights leads traffic across the bridge at a safe speed.
Transportation
Outcome: Although
labor-intensive, the warning system has improved safety by reducing average
speed and minimizing crash risk in low visibility conditions.
Implementation Issues: The original system design included a vehicle detection subsystem, backscatter visibility sensors, and automated activation of signs. Bridge deck construction precluded the installation of inductive loop detectors and vibration prevented the use of microwave vehicle detectors. Thus, the vehicle detection subsystem had to be eliminated. Visibility sensors with backscatter technology were deployed along the bridge in Fall 1999. However, problems with accuracy a