May 22 - July 28
Comparing Road and Bridge Surface Temperatures During the Winter Season in Ohio
Seth Guidry, Daniel Tripp, Mike Baldwin, and Andrew Rosenow
What is already known:
- Winter weather has a major impact on adverse road conditions in the United States, especially during the winter months.
- Bridges tend to ice before roads because they have more surface area exposure to cold air temperatures, while roads have extra heat insulation from the ground.
- In 2020, the National Severe Storms Laboratory (NSSL) developed the Probability of Subfreezing Roads (ProbSR) model which provides accurate and efficient predictions of below freezing temperatures on road surfaces.
- One limitation of the ProbSR model is that it does not discriminate between road and bridge surfaces, which may cause an underprediction of bridge surface temperatures.
What this study adds:
- This study investigates the differences between road and bridge surface temperatures by analyzing data collected from Road Weather Information System (RWIS) stations across Ohio during the 2022-2023 winter season.
- When surface temperatures are cold, roads are more likely to be warmer than bridges.
- At warmer surface temperatures, neither bridge nor road is significantly warmer than the other.
- During the winter season, bridges are often below freezing while roads remain above freezing.
- Differences in surface temperature and air temperature provided some insight into distinguishing between roads and bridges, especially in extremely cold conditions.
- There’s not much of a difference between road and bridge surface temperatures when the air temperature is at freezing, which is normally when significant icing events occur.
Abstract:
Unfavorable road conditions due to winter weather have major impacts throughout the United States. Though transportation agencies take measures to prevent freezing precipitation from accumulating on highways, one critical challenge is knowing when road surfaces are sub-freezing. With this motivation, the National Severe Storms Laboratory (NSSL) created a probabilistic model that predicts the likelihood of sub-freezing roads within the U.S. However, one major caveat of this model is that it does not differentiate between road and bridge surfaces, and bridges are commonly known to ice before roads do. This study investigates how road and bridge surface temperatures differ throughout the 2022-2023 winter season using hourly road sensor observations from Road Weather Information System (RWIS) stations in Ohio. Air temperature readings from RWIS towers are used to compare how bridge and road surface temperatures behave in cold environments. Results suggest that roads are typically warmer than bridges when both surface temperatures are below/near freezing. Additionally, if only one surface is below freezing, it is most likely to be the bridge rather than the road. Differences between air and surface temperatures also provide some evidence that suggests surface temperatures on bridges act differently than surface temperatures on roads. However, in environments near freezing (0°C), both road and bridge surfaces are typically 1-3°C warmer than the air temperature. Since roads and bridges behave similarly near 0°C, this suggests that a separate model for bridges may not be necessary as these small deviations will unlikely result in significant changes to the probabilistic output of the model.