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Road Weather Information System
Environmental Sensor Station
Siting Guidelines
April 2005

Appendix D - ESS Checklist

This checklist is a synopsis of the siting criteria contained in the main document. The checklist provides an organized list of considerations for uniform siting of ESSs. Section numbers refer to locations in the main document.

Identify Road Weather Data Requirements and Uses (Section 2.0)

  • checkbox Detect or monitor roadway conditions.
  • checkbox Support winter maintenance decisions.
  • checkbox Support road temperature modeling.
  • checkbox Support improved weather forecasts.
  • checkbox Warn travelers of road conditions.
  • checkbox Help manage traffic.
  • checkbox Support road construction.
  • checkbox Other uses.

Identify Basic Requirement for the Site

  • checkbox Regional site to provide road and weather data representative of a general area. Generally used to monitor the onset or existence of predicted conditions and to provide information used to forecast weather and road conditions. (Section 2.2)
  • checkbox Local site used to detect existing or changing conditions at a specific site or to provide a predictor for the condition and site. (Section 2.2)

Identify Candidate Locations for the Site

  • checkbox Choose candidate locations based on site requirements.
    • checkbox For a regional site, select relatively flat, open terrain removed from local non-weather influences. (Section 3.1)
    • checkbox For a local site, select candidate locations close to the road weather condition or road segment of interest or in a position specifically selected to detect and/or predict a local roadway condition (e.g., smoke or dust sources, canyon entrances, sources of road flooding). (Section 3.2)
  • checkbox Identify power source options and challenges (type, access, cost). (Section 5.2)
  • checkbox Identify communications options and challenges (type, capacity, frequency of access, cost). (Section 5.3)
  • checkbox Other considerations (aesthetics, safety, security). (Section 5.4)
  • checkbox Investigate opportunities to partner with other agencies. (Section 5.3).
    • checkbox Identify other sites or sensors to provide weather data that can be used to monitor or predict road weather conditions.
    • checkbox Identify infrastructure resources (power, communications, sensor platforms) that can support ESS installation.
  • checkbox Verify the availability of rights of way to install the site. In some cases, easements or other permits may be required. (Section 4.0)

Identify Sensors Needed

  • checkbox Choose sensor suite-based requirements.
    • checkbox For a local condition or regional site. (Section 2.1)
      • checkbox Consider how the observations will be used.
      • checkbox What are the required weather parameters at the site of interest and what sensors can measure them directly or provide an indication of their occurrence?
    • checkbox For a regional site. (Section 2.1)
      • checkbox Select a minimum suite of initial sensors for area coverage based on agency needs.
        • checkbox Wind speed and direction.
        • checkbox Temperature/dewpoint.
        • checkbox Pavement surface conditions.
        • checkbox Precipitation presence, type, and intensity.
  • checkbox Consider additional sensors. (Sections 2.1 and 4.3 and Appendix C)
    • checkbox Assess requirements, usefulness, sensor reliability/maintainability, and cost.
      • checkbox Atmospheric pressure.
      • checkbox Subsurface temperature.
      • checkbox Visibility.
      • checkbox Precipitation accumulation.
      • checkbox Solar/terrestrial radiation.

Select a Specific Site

  • checkbox Assess surroundings. (Section 4.0)
    • checkbox Identify potential obstructions to selected sensors.
    • checkbox Identify potential sensor contaminants.
      • checkbox Nearby water/dust sources, tree/terrain shadowing.
  • checkbox Identify tower site (trade-offs required). (Sections 4.0 and 4.1)
    • checkbox Assess distance from obstructions/contaminants.
    • checkbox Assess specific power/communications access.
    • checkbox Assess ease of maintenance and safety considerations for road traffic and maintenance personnel.
  • checkbox Identify pavement surface sensor locations and lane placement to meet operations and road maintenance requirements. (Section 4.2)
  • checkbox Identify site(s) for additional sensor(s) separate from tower. (Section 4.0)

Tower and Sensor Siting Recommendations

  • checkbox Site tower. (Sections 4.1 and 4.2)
    • checkbox Flat terrain, not bedrock or swampy, no steep slope within 300 feet (approximately 90 meters).
    • checkbox Low vegetation/native soil for 50 feet (15 meters).
    • checkbox Upwind of roadway for season of interest.
    • checkbox Avoid standing water.
    • checkbox Position 30 to 50 feet (9 to 15 meters) from edge of paved surface.
    • checkbox Height of tower depends on selected sensor suite; at least 33 feet (10 meters) for wind sensors.
    • checkbox Tower base at the same elevation as road surface, if possible.
    • checkbox Barrier or guardrail.
    • checkbox Security fence.
    • checkbox Avoid neighboring structures, signs, and trees or tall vegetation. Towers with wind sensors should be located away from obstacles at a distance of at least 10 times the height of the nearest large obstacle, if possible.
  • checkbox Site sensors.
    • checkbox Atmospheric temperature/dewpoint. (Sections 3.2.2 and 4.2)
      • checkbox Shielded, well-ventilated sensor.
      • checkbox Height of sensor 5 to 6.5 feet (1.5 to 2 meters).
      • checkbox Boom extended from tower at least 3 feet (1 meter).
      • checkbox For local low-visibility conditions, consider alternate siting closer to the road or local sources (moisture/dust) to capture local effects.
    • checkbox Wind speed and direction. (Sections 3.2.3 and 4.2)
      • checkbox Locate the sensor away from obstacles at a distance of at least 10 times the height of nearest obstruction, if possible.
      • checkbox Height of sensor 33 feet (10 meters).
      • checkbox For high wind conditions, consider:
        • checkbox Siting additional sensors at a 10 to 16.5 feet (3 to 5 meters) height to capture local effects.
        • checkbox Locating sensors at the entry and/or exit of valleys or canyons to measure high winds due to channeling.
    • checkbox Optically-based precipitation (rate, type, and amount). (Section 4.2)
      • checkbox Height of sensor 10 feet (3 meters).
      • checkbox Avoid sun or stray light sources.
    • checkbox Visibility. (Sections 3.2.2 and 4.2)
      • checkbox Height of sensor 6.5 to 10 feet (2 to 3 meters).
      • checkbox Avoid sun or stray light sources.
      • checkbox For local low-visibility conditions, consider alternate siting closer to the road or local sources (moisture/dust) to capture local effects.
    • checkbox Snow depth. (Section 4.2)
      • checkbox Height of sensor approximately 3.5 feet (1 meter).
      • checkbox Ensure proper field of view and orientation.
    • checkbox Shortwave solar radiation. (Section 4.2)
      • checkbox Height of sensor at least 10 feet (3 meters).
      • checkbox Avoid reflective surfaces and shading.
    • checkbox Longwave radiation. (Section 4.2)
      • checkbox Height of sensor at least 10 feet (3 meters).
      • checkbox Ensure clear field of view.
    • checkbox Cameras. (Section 4.2)
      • checkbox Site as high as possible to obtain clear line-of-sight or at driver’s level, depending on requirement.
      • checkbox Ensure non-interference with other sensors.
    • checkbox Pavement temperature and pavement condition. (Sections 3.2.1 and 4.2)
      • checkbox For local slippery pavement conditions, select location to capture critical condition.
      • checkbox In user-specified lane near edge of wheel track, flush with surface.
      • checkbox Avoid pavements with ruts or depressions that cause ponding.
      • checkbox Avoid shade, unless specific requirement dictates.
      • checkbox Utilize junction and pull boxes for ease of installation and replacement.
    • checkbox Subsurface temperature/moisture. (Section 4.2)
      • checkbox Depth of sensor 12 or 18 inches (30.5 or 45.5 centimeters).
      • checkbox Avoid burying under pavement sensors.
    • checkbox Precipitation accumulation. (Section 4.2)
      • checkbox Place in as open an area as possible.
      • checkbox Consider separating from other sensors rather than mounting on the tower.
      • checkbox Consider power requirements for winter operation.
    • checkbox Barometric pressure. (Section 4.2)
      • checkbox Avoid exposure to elements and wide temperature changes.
    • checkbox Water level sensors. (Section 4.2)
      • checkbox Place in low-turbulent (i.e., steady flowing) portion of the flowing creek or river.
      • checkbox If installed on or next to a bridge, locate on the downstream side.
      • checkbox For roadway monitoring, place the sensor adjacent to the low point of the road segment subject to flooding.

Metadata (Section 5.6)

  • checkbox Document site specific installation details.
  • checkbox Update these data whenever changes are made to the ESS installation.
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