The initial review of the Guide consisted of a survey of State DOTs with active RWIS programs and subsequent analysis of the survey results. Preliminary recommendations for enhancements were distilled from the analysis. Inclusion of a recommendation in this analysis, however, does not necessarily predict a corresponding change in the Guide. Recommendations that would increase the scope of the Guide, for example, are included for completeness in this report, but will not result in any changes to the Guide.
3.1 Results from Survey of DOT ESS Implementers
Fifteen DOTs were contacted to discuss their familiarity and experience with the Guide. Of the nine respondents, eight were familiar enough to discuss the Guide, and one referred to its consultant, who had used the Guide to design a major ESS deployment. Overall impressions of the Guide were positive. Most respondents felt it was useful, some as a guide, others as a check against their own procedures. Coordination of ESS with other intelligent transportation system (ITS) technologies such as dynamic message signs (DMSs), closed-circuit television (CCTV) cameras, and bridge anti-icing spray systems was mentioned as an emerging area that needed more attention. Flooding was another concern raised. Water level gauges, possibly deployed with roadway warning signs, could be deployed along with standard ESSs in these situations. Deployment of mobile sensors on agency maintenance vehicles was another. Most of the DOTs interviewed have significant RWISs but most said they are only planning limited expansion, with funding as the primary concern.
Survey Respondents
- Iowa DOT – Tina Greenfield
- Idaho Transportation Department (ITD) – Bryon Breen
- Iteris (consultant to ITD) – Todd Hoffman
- Utah DOT – James Dziatlik
- Colorado DOT – Philip Anderle
- Wisconsin DOT – Michael Adams
- Kansas DOT – Peter Carttar
- Alaska DOT & Public Facilities– Jack Stickel
- Nevada DOT – Denise Inda
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3.1.1 Familiarity with Guide
All of the respondents were familiar with the Guide, although one or two respondents said they only had passing familiarity. Several had been involved in the development and review of the Guide, had read through it and were familiar with the siting recommendations in detail. Other respondents had either skimmed through the document or read specific sections that were relevant to their concerns. One respondent had used it in a siting project while several others used them as a check against their own procedures and guidelines.
Most respondents felt that the Guide was useful in siting decisions and was relatively easy to follow. The checklist in Appendix D of the Guide, which provides a synopsis of siting criteria contained in the main document, was noted by a number of respondents as a very useful tool. They said that it provided a sound, structured approach, and helped confirm that they considered all the important factors in siting an ESS. Most respondents felt that the document effectively covered the key factors in siting, without being too long or overly technical. Some consider it more of a reference document than a set of guidelines, something to use to find specific pieces of information or address specific concerns.
One respondent noted that the Guide leans heavily toward meteorological considerations and could benefit from more consideration of transportation concerns. Another had a similar comment that the Guide is stronger on representative sites than location-specific sites, even though both are covered and the difference is explained. Another respondent, who is a meteorologist, felt the emphasis on meteorological concerns is beneficial, since most of the DOT personnel responsible for ESS installation do not have a meteorological background. Most respondents understood that siting almost always requires a compromise between meteorological concerns and roadway maintenance concerns.
One respondent noted that knowledge of available technology helps to achieve an optimal balance between operational (for example, power) and meteorological concerns. In this case, the respondent’s agency uses a portable, modular generator for remote sites where power is not available. The unit operates on propane and only needs to be accessed every six months. Another tradeoff issue mentioned was the desire to locate ESSs on State property rather than on adjacent private land. In some cases, private property may be advantageous from a meteorological perspective, but this advantage must be very significant in order to justify the additional time and expense needed to lease or appropriate property.
There was an interest in providing more information in the Guide on ESS siting in conjunction with ITS components such as cameras and DMSs. Cameras were mentioned as being very helpful in areas of heavy snow depth, to give winter maintenance personnel a better idea of conditions that they will face in the field. One respondent noted that bridge anti-icing spray systems are becoming more popular and that ESS siting issues related to these systems should be covered. One respondent noted that DOT personnel would like a better understanding of what makes weather observations acceptable to the meteorological community. The document gives a partial explanation in that regard, but more information would be helpful. Compatibility with Clarus was another issue that was raised by several respondents. Two respondents also mentioned that MDSS data requirements were an important consideration in their ESS deployment strategies. One respondent mentioned the importance of metadata, which is covered in the Guide. It was noted that the reasons for providing metadata should be highlighted since their importance is recognized within the meteorological community but not to the same degree within the State DOT community.
Another respondent felt that the Guide should state the importance of ongoing maintenance on ESS accuracy. Information should be included on how the location of the station impacts the ability to effectively maintain the sensing devices.
3.1.2 ESS Deployment Activities
Most of the respondents did not have major ESS deployments underway during the survey. The one exception was Idaho, which was in the process of deploying 50 ESSs around the state at the time of the survey. The Idaho Transportation Department (ITD) asked its design consultant to use the Guide in its design effort. The consultant used the Guide and found it easy to implement and very helpful in identifying the full range of concerns that need to be addressed in ESS siting. They noted that the Guide added technical rigor to their process and led to location changes for a number of sites.
One agency that used the Guide as a check against their own process said that in retrospect they would have used the Guide more formally to avoid some problems that have been experienced with specific sites in a recent major deployment. Some decisions that have caused both maintenance problems and data quality problems probably would have been made differently. Several respondents said that the Guide would have been helpful in recent deployments. Some basic siting mistakes were noted, such as locating a solar-powered sensor in an area that was shaded a large percentage of the time, or locating a camera in a spot subject to high winds and low visibility.
Most of the responding agencies said they were either adding small numbers of ESSs or upgrading existing stations. Several noted that their systems were relatively mature and they did not anticipate significant new deployments in the near future. Most noted they are adding ESSs in small numbers or relocating some of them as part of larger roadway projects. Others are interested in expanding their RWISs but are having difficulty obtaining the funding. Several noted they are adding ITS technology to existing ESSs, including DMSs that will warn of high winds or wet/icy conditions on downstream roadway sections. Several respondents also noted they are concentrating on improving their communications infrastructure for existing ESSs. Improved wireless systems are being implemented at some locations where communications problems have been experienced in the past. As improved systems come on the market, greater flexibility in siting ESSs may result.
One respondent mentioned that his department is in the process of outfitting most of their vehicle fleet with weather sensors. They felt that mobile sensors will be a growing area of importance and that the Guide should be expanded to address these.
3.1.3 Use of Guide
None of the other respondents had used the Guide in the same way as Idaho, as the primary source for siting decisions. Several agencies, however, noted that they have used them as general guidance or have checked their own guidelines to see how well they matched. Those who did the latter felt that their own guidelines were generally in line with those of FHWA. Most of the respondents said that they expected to use the Guide going forward in some fashion. Some plan to use them as a primary source of information while others will use them as a check on their own guidelines or procedures.
3.1.4 Current Siting Standards
About half the respondents had existing guidelines but in most cases they were informal and oriented toward location-based deployments. For example, those guidelines may have noted items like height, acceptable distance from the road, structural and power requirements. For location-based ESSs, most DOTs rely on information from their District maintenance personnel. Areas that freeze quickly or roadway segments that are more susceptible to accidents are given higher priority. Utility access is a primary concern of most agencies as well. Some of the respondents have a checklist similar to that in Appendix D of the Guide, but include fewer specific items. Some of the respondents indicated that the guidelines they have are not meteorologically-oriented and that they could use additional help from the Guide.
3.2 Analysis
Respondent comments on the Guide were oriented along operational lines, and did not necessarily relate to a particular section of the Guide. There was a consistent interest among respondents in better documentation of how the Guide can be used by transportation agencies. The survey revealed, for example, that whereas it is the exception today to have used the Guide as the basis for ESS deployments, virtually all DOT personnel with knowledge of the Guide have used them as reference material and to support or supplement their own guide. This suggests that there may be value in adding text to the document describing “How to Use this Guide”. Both new and previous users would benefit from insights provided by the growing base of DOT experience with the Guide.
One approach to documenting the utility of the Guide would be to recognize and emphasize its fit within the systems engineering principles of ESS deployments. While the Guide recognizes ESSs as components of an ITS, the guidance therein is not explicitly structured around a systems engineering approach. The National ITS Architecture and systems deployed within the context of a Regional Architecture are conditioned to a systems engineering model, and it would benefit the Guide to conform to that model as well. To that end:
- Section 1, “Introduction”, contains many of the elements of a Concept of Operations for DOT RWIS and ESS deployments. A more focused discussion of user needs and description of usage scenarios would identify more specific requirements for particular applications.
- Section 1 also contains descriptions of RWISs and ESSs, and categorization of sensors. This discussion could be expanded and integrated with a description of the system’s relationship to the ITS architectures to provide a more comprehensive basis for the system design.
- Section 2, “Assessing Road Weather Informational Requirements”, provides extensive discussion of potential system requirements. It does not, however, provide traceability to user needs or application scenarios. The same requirements could be more explicit in the Appendix D “ESS Checklist”.
- Sections 3 (“Site Selection”) and 4 (“Recommended Siting Criteria”) generally describe considerations to be included in designing an ESS deployment. The guidance is extensive, but would benefit from being traceable to specific requirements and user needs.
- The contents of Section 5, “Additional Considerations,” could be redistributed among the other sections without any loss of information and with value added by restoring context to each consideration. For example, “Siting Considerations”, “Power”, and “Communications” could be included with the requirements as constraints on the design. The “Siting Metadata” discussion could be incorporated into an architectural discussion.
- Section 5 also describes “Siting Reevaluation”. This description could be one piece of a larger discussion of deployment and maintenance of the ESS as it relates to the system life cycle.
This more explicit alignment of sections in the Guide with steps in a systems engineering process allows the operational issues highlighted in the survey responses to flow consistently through ESS design and deployment.
3.2.1 Introduction to RWIS ESS Concepts
The current “1.0 Introduction” section of the Guide provides excellent background information on ESS operations and equipment. It discusses the scope and purposes of the Guide itself, with a brief description of ESSs and the benefits of ESS data. As noted earlier, the Introduction serves the systems engineering purpose of a Concept of Operations.
With this purpose, the Introduction should provide a perspective that encompasses a broader view of road weather information applications and the RWIS ESS as a means of fulfilling the data needs of those applications. The current Guide text provides an overview of the flow and use of the data, but does not link the data to specific applications. Data applications are listed as benefits of deploying ESS, but the relationships between applications and the data needed to support them are not explicitly stated. For example, transportation agencies might be interested in incorporating weather information into traffic management decisions in a variety of modes and methods. Signal timing plans for adverse weather conditions could be developed for major corridors. Agencies might mandate or recommend a lower speed on limited access highways rather than simply warning of adverse conditions ahead. In order to implement these types of strategies, transportation agencies must have a clear understanding of the availability and accuracy of ESS data.
ESS siting decisions will have an impact on both the development and the implementation of weather-responsive traffic management strategies. While this document is not intended to discuss weather-responsive traffic management strategies in detail, a brief narrative and table with the implications of weather-responsive traffic management strategies on ESS siting would be helpful. It should include roadway monitoring, winter maintenance, signal timing strategies, traveler information, and management strategies for major incidents or construction. The information may be general at first with greater detail added over time as more agencies gain experience with these strategies.
In this context, the Introduction section of the document should describe the user needs and constraints to be considered in development of the RWIS program plan. This is particularly true in the case where the needs are many, but resources are constrained. Agencies implementing RWIS ESSs want to know how to characterize and assess the trade-offs among competing needs for road weather information. While the Guide provides a list of significant benefits, there is a need for corresponding guidance on the relative costs of implementation to meet particular operational needs. The cost data would enable agencies to make more informed deployment plans. Prioritization within the plan is an essential step in establishing the agency needs for data, which then become the basis for assessing the informational requirements in the next section of the Guide.
For example, agencies surveyed on their ESS deployment experience consistently indicated that maintainability of the ESS was, in hindsight, a major deployment constraint. The Guide should provide greater prominence to the need to maintain ESSs, as well as some indications of best maintenance practices, and how these practices impact siting decisions. Technological advances in areas such as remote diagnostics could be discussed, along with the impact that these changes may have on siting decisions. Communications technology and power generation could also constrain maintenance needs. The impact of maintainability needs could then be revisited in the requirements and siting criteria sections of the Guide.
The broad view of RWIS ESS deployments is also incomplete without some discussion of the Clarus Initiative. FHWA’s Clarus Initiative is an example of the tremendous opportunities for making ESS observations available across larger regions and jurisdictional boundaries. Observations fed to Clarus from DOT ESSs are quality checked and disseminated throughout the transportation and meteorological communities for developing value-added products and services. The DOTs providing their observations to Clarus then have access to the quality checks performed on their environmental data, to similar data from other jurisdictions, and to the value-added products.
Agencies participating in the Clarus Initiative would benefit from a discussion of these opportunities in the Guide. It is recommended that Clarus background information be included in the revised Guide, and that the impacts of Clarus on siting, if any, and on collection of ESS metadata (as described below) be integrated elsewhere in the document as appropriate.
3.2.2 RWIS and ESS Requirements
The Guide section on “Assessing Road Weather Information Requirements” provides a bridge from the road weather concepts in the Introduction to the siting details in subsequent sections. The text discusses the planning for ESS acquisition and installation, describes the kinds of sensors generally available for ESSs, distinguishes between regional and local installations, and describes opportunities for road weather information partnerships. The core of the requirements discussion relates to the distinction between regional and local implementations, and should be expanded.
For example, there is a growing recognition among DOTs deploying ESSs that there may be operational benefits to coordinating the deployment of ESSs with other ITS components.
- Dedicated bridge anti-icing spray systems could be coordinated or integrated with traditional ESSs to provide more detailed road and bridge weather information to winter maintenance and meteorological staff;
- Precipitation sensors could be deployed with CCTV cameras to provide mutual confirmation of precipitation observations;
- A DMS coordinated with an ESS could provide real-time “on-the-ground” warnings of adverse weather conditions to travelers; and
- Water level sensors in flood-prone areas and snow depth sensors in areas prone to drifting are two weather-related technologies that can be integrated with ITS.
ESSs currently installed across the United States are providing valuable road weather data to the DOTs, but most of them are not coordinated or integrated with existing ITS technologies. Operational and safety benefits could accrue from coordination in both localized deployments (like bridges subject to high winds) and regional integrations (perhaps in support of MDSS and winter maintenance operations). In other words, the requirements for ESS siting need to be traceable to the intended applications and user needs.
3.2.3 Site Selection Guidelines
The “Site Selection” section of the Guide describes the rationale by which DOT planners may make ESS deployment decisions and the circumstances associated with particular types of sites. The guidance covers the cases for regional and local sites, and provides a brief discussion of siting tools that may be helpful in the site selection process. The bulk of the text is focused on guidelines for siting ESSs in response to local road weather data requirements. The text is very informative and focused. In the context of the systems engineering process, this section fulfills the intent of a system architecture or high-level design.
As part of the discussion of siting tools, this section includes a discussion of portable sensor systems. The text notes that such systems are useful for temporary monitoring of certain locations and for “scouting” of locations for permanent ESS sites. This section would benefit from extending this discussion from portable versions of existing ESS platforms to truly mobile systems. Road weather sensors have been successfully used on DOT maintenance vehicles for many years, and technology is making the sensors more accurate and thus more useful in identifying specific problems and contributing to more general weather data collection. Higher quality data from vehicle “black boxes” are likely to become more available, especially from agency-owned vehicles, and this data source will provide useful information on surface conditions. Telematics solutions could dramatically change the way road weather information is collected and processed. It is important that the Guide discuss these developments, even if the Guide is otherwise intended specifically for fixed ESS installations.
3.2.4 Recommended Siting Criteria
The “Siting Criteria” section of the Guide provides specific guidance on the design of the ESS observation tower and placement of sensors. The guidance reflects an extensive body of experience from transportation agencies and the broader weather community. This section fulfills its intent with no apparent need for improvement.
3.2.5 Additional Considerations
The “Additional Considerations” section of the Guide generally addresses siting considerations not directly associated with weather-related aspects of the ESS. Topics covered in this section include power supply to the ESS, communications, site access (aesthetics, safety, and security), periodic site reevaluation, and siting metadata. Any ESS deployment will have to deal with these considerations as part of the planning and design of the sites.
Among these considerations, the increasing extent and sophistication of ESS deployments have brought increased attention to the need for better data about the ESS (metadata) with which to manage their deployment. To that end, several State DOTs have put significant effort into improving the collection, quality assurance, and maintenance of this metadata. In addition, the Clarus Initiative needs high-quality metadata to reliably gather and check the quality of observations provided by the contributing DOTs. A Metadata Task Force was convened by the FHWA as part of the Clarus Initiative to prepare recommendations for prioritization and standardization of meteorological metadata for transportation applications.
Tables 2 and 3 of the Guide provide classification, structuring, and specifications for ESS metadata. Supporting text generally describes the need for metadata and standardization efforts underway within the National Oceanic and Atmospheric Administration (NOAA). The tables themselves describe metadata components and distinguish between those that are recommended and those that are supplemental. Many of the metadata descriptions correspond closely to data described in the National Transportation Communications for ITS Protocol Environmental Sensor Station Interface Standard, NTCIP 1204, for object definitions.
Metadata treatment within the Guide could be significantly enhanced by:
- Incorporation of the Clarus Metadata Task Force recommendations (These recommendations, in the form of the Clarus Metadata Dictionary, are available online at http://www.clarusinitiative.org/documents.htm);
- A more robust and complete comparison of metadata recommendations from Clarus, NTCIP 1204, and any NOAA standards; and
- Provision of metadata checklists or tools implementing those recommendations.
Section 6 of this report explicitly addresses these factors in the treatment of metadata in the Guide.
3.2.6 ESS Checklist
Appendix D of the Guide provides a checklist summarizing the key points from the body of the document. The checklist is in the form of an outline that roughly follows a typical planning and deployment process. Specific siting and sensor configuration criteria are included in appropriate contexts within the checklist.
The checklist should be updated for any changes or extensions to material in the body of the Guide. In particular, as discussed earlier in this evaluation, the checklist should be updated to include discussion of constraints and prioritization among sites being considered (Section 3.2.1) and discussion of integration with other ITS considerations (Section 3.2.2).
