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Weather Applications and Products Enabled Through Vehicle Infrastructure Integration (VII)

2. Introduction

THE NEED FOR ENHANCED ROAD WEATHER INFORMATION


An investigation of crashes occurring from 1995 through 2004 revealed that each year there are over 1,500,000 crashes that occur during poor weather conditions, resulting in more than 690,000 people injured and nearly 7,400 fatalities (1). It is worth noting that these figures are considerably higher than any other mode of transportation (e.g. aviation, rail, marine, etc.). The majority of the weather-related crashes (76%) occurred when roadway surfaces were wet, while 10% of all weather-related crashes took place during snowy or slushy driving conditions.

Adverse weather not only affects safety, but leads to degradations in mobility and efficiency. Depending on the time of day and the weather conditions, traffic flow along signalized arterials can be reduced anywhere from 6% to 30% during adverse weather. Additionally, vehicle speed is reduced by 10% to 25% when conditions include wet pavement and rain. During situations when roads are snow covered and/or slushy, vehicle speeds can decline as much as 40% (2,3). As might be expected, flow rate degradations and speed reductions directly contribute to increased travel times. Under extreme conditions (e.g. snowstorms), travel times can increase by as much as 50% (2).

In an effort to mitigate the impact weather has on the national roadway system, several recent reports (4,5,6) have highlighted the need for:

Vehicle Infrastructure Integration (VII), which involves vehicle-to-vehicle and vehicle-to-infrastructure communications through Dedicated Short Range Communications (DSRC-wireless radio communication at 5.9 GHz), has the potential to facilitate advancements in each of these areas, possibly fostering improvements in the accuracy and timeliness of road weather information. Such improvements could also translate into new and improved decision support tools and products for the surface transportation community.

There is a critical need for high-resolution (spatial and temporal) atmospheric and road condition data. These data should include measurements of parameters within the atmospheric boundary layer (ABL)1, as well as surface and subsurface measurements. VII will enable direct measurement of select atmospheric variables and indirect assessment of road conditions at high spatial and temporal frequencies. Together this information will lead to advanced road weather analyses and forecasts, and it would advance the state of understanding as it relates to how weather and road conditions impact the U.S. roadway system.

In terms of improving road weather forecast capabilities, the availability of VII-enabled data may result in substantial improvements in the ability of numerical weather prediction models to accurately forecast changes in the atmosphere, including the ABL. Accurate forecasts of atmospheric boundary conditions are dependent on four primary factors: the spatial resolution of the weather prediction model; the effective simulation of atmospheric dynamics at various scales; the physical parameterization scheme used to characterize surface and turbulent processes; and the ability to accurately analyze the initial atmospheric structure and surface parameters (7). While the capacity of numerical models to forecast surface conditions is reliant on more than simply defining the initial state of the atmosphere, it is clear that an accurate characterization of the atmospheric conditions is an important element in the prediction process. Coupling improvements in atmospheric numerical models with soil models that track the energy and water budget will also directly benefit road condition forecasts.

It is anticipated that data derived from vehicles and transmitted to the VII infrastructure will be made available to integrated observation networks and data management systems. For example, it is envisioned that weather and road condition related vehicle data elements will be included in the Clarus system, a network designed to collect, quality check, and disseminate atmospheric, hydrologic, and pavement data through on-demand and subscription-based services (8). The Clarus system is part of a larger initiative sponsored by the Federal Highway Administration (FHWA) dedicated to acquiring, organizing and distributing roadway environmental sensor station data in support of diagnosing and predicting atmospheric and road conditions that impact the surface transportation community.

VII presents a new technology that will improve road weather information and products by facilitating the communication of weather and road condition data to and from vehicles and other transportation decision support systems and stakeholders. In-vehicle information systems, the national 511 traveler information system, traffic management centers, traffic operation centers, maintenance managers, dispatch operations, and others should benefit from VII-enabled data and related applications. In terms of weather-related information and products, the VII architecture should lend itself to providing raw data, post-processed data, and application based solutions to stakeholder communities.

The goals of this report are to: (1) provide a basic understanding of current and future vehicle data elements that have the potential to be used directly or indirectly to sense weather and road conditions; (2) examine the potential contribution of VII derived atmospheric and road condition information in the analysis and prediction of weather-related hazards; (3) identify technical issues and barriers that may impact the development and implementation of weather-related VII applications; (4) outline research topics that need to be addressed to fully utilize vehicle data in improving road weather products and services; and (5) summarize the viability of utilizing VII-enabled data in weather and road condition applications designed to improve surface transportation safety, mobility, and efficiency.

This document contains forward-looking statements regarding the use of VII-enabled data in the development of road weather products and applications. The assertions made herein are based in part on the current state of understanding as it relates to the VII architecture, probe message processes, and surface transportation weather. There are a number of important known and unknown risk factors and uncertainties that will affect the beliefs, ideas and claims expressed herein, some of which are described in detail.

1 The lowest layer of the troposphere where air flow is influenced by friction of the Earth's surface. The atmospheric boundary layer, on average, ranges from the surface to approximately 1 kilometer (3,300 feet).

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