WTI

Development of a Roadway Weather Severity Index (Showcase Evaluation #16)

Primary Investigator Contact Information

External Project Contact(s)

Report(s)

1. Development of a Roadway Weather Severity Index--Final Technical Report
   1. Christopher Strong, Yurri Shvetsov, Julia Sharp
   2. 426711_Final_Report.pdf

Project Objective

The purpose of this study is to research and develop a weather severity index that would be appropriate for roadways. The objectives of the index are to correlate with winter maintenance costs, correlate with the relative hazards of weather-related driving conditions experienced by motorists, use data that is already available, and be easy-to-use and interpret.

Project Abstract

Weather can have a significant impact on rural highway operations. For example, highway agencies in the United States spend more than $2 billion per year on winter maintenance activities. Adverse winter weather, along with other weather challenges such as fog, rain, and wind, can significantly increase crash frequency on otherwise benign roadways. Because of the significant variability in weather across years during the same season, it is difficult to quantify the effect that weather may have, positively or negatively, on highway operations. It is also difficult to “correct” for the effects of weather when identifying the advantages or disadvantages of various operational and safety improvements. A weather index for roadways would help in such situations. Although a weather severity index for roadways has not been developed, severe weather indices have been developed for application in many other fields, such as wildlife ecology, icebreaking on the Great Lakes, and degree days for household utilities. In every case, these indices tend to have higher values with more extreme (e.g. colder or hotter) weather. For surface transportation, extreme conditions may not necessarily be the best measure of weather severity. Moreover, while daily or monthly averages may be adequate for other applications, it is not clear whether this is true for surface transportation. The purpose of this study is to research and develop a weather severity index that would be appropriate for roadways. The desired attributes of the index are as follows.§ The index would directly correlate with winter maintenance costs. For example, a 10 percent increase in the index value might equate to a 10 percent increase in maintenance costs.§ The index would correlate with the relative hazards of driving conditions experienced by motorists, including snow, blowing snow, ice, frost, rain, fog and wind. This correlation could be shown by the relative accident frequencies on the same segment of roadway during years of significantly differing weather conditions.§ The index would use data that is already available, such as through the National Weather Service (NWS) or RWIS stations.§ The index would be easy to use and interpret.

Task Descriptions

1. Project Management
   1. This task covers overall project management activities to track project progress.
2. Review of Other Weather Indices
   1. This task will document weather indices that have been developed in other fields. Potential indices include, but are not limited to, those cited earlier.
3. Index Refinement
   1. Based on the findings of Task 6, the indices will be refined. Additional calibration or validation may then be necessary for the indices. More fundamentally, however, there may be a reduction in the number or type of indices, if some indices fail to provide useful or accurate information.
4. Review of Available Data
   1. This task will review data sources that may be used for this project, including weather data, winter maintenance cost data, and crash data.
5. Stakeholder Outreach
   1. The purpose of the stakeholder outreach task will be to identify what factors that transportation system operators, especially maintenance personnel, believe contribute to the severity of weather for surface transportation.
6. Final Report
   1. This task will document all information collected under the previous tasks. It will also present the refined version of the index or indices, with detailed descriptions of data sources, interpretation guidelines, and results of calibration and validation.
7. Index Testing
   1. This task will use weather forecast data that may be available to determine the accuracy, effectiveness and usefulness of the indices developed in Task 5.
8. Development of Indices
   1. This task will seek to develop one or more indices that may be used for assessing roadway weather severity. The number and nature of indices will be determined based on the findings of previous tasks. Separate indices may be required for different correlative purposes, such as one index for maintenance costs and another for crash data. In addition, separate indices may be developed for different types of weather conditions, such as a fog severity index.

Milestones, Dates, Schedule

Student Involvement

False

Relationship to Other Research Projects

True

Technology Transfer Activities

True

Transportation Research Board Keywords

detectable warning surfaces, maintenance, weather, surface transportation

Partners

Caltrans, ODOT, Research and Innovative Technology Administration