Showing papers in "Transportation Research E-Circular in 2012"

Alternative Approaches to Measuring Deicer Ice-Melting Capacity: Optimization of Test Accuracy and Precision

Abstract: The current industry standards for measuring ice-melting capacity are the Strategic Highway Research Program (SHRP) methods H-205.1 and H-205.2. Depending on the test conditions, the accuracy and precision of the method can vary greatly. Ice-melting capacities measured using standard application rates are not always accurate measurements of total ice-melting capacity. It is important to understand the effect of test conditions on the results of the SHRP ice-melting capacity test so that the results can be correctly understood and applied. The authors have carried out an analysis of variance of the SHRP ice-melting capacity test under different conditions of application rate, temperature, and time. The data show that total ice-melting capacities are underestimated at low application rates and tend to converge on a constant value at high application rates. The data also show that test precision can be increased substantially by using higher application rates and longer measurement times. An alternative ice-melting capacity test in which ice cubes are allowed to melt in concentrated solutions of deicers until equilibrium is reached is also presented; ice melt quantity is determined by weight gain in the deicer solution, reducing the error associated with incomplete recovery of melt from the ice surface in the SHRP test. The data are presented with a discussion of the importance of distinguishing ice-melting rate from total ice-melting capacity, the relevance of this to deicer residual effect, and the utility of precise measurements in determining the effect of low-level additives in deicer blends.

Applications of Advanced Models to Understand Behavior and Performance of Asphalt Mixtures

Abstract: This E-Circular is a synopsis of current information on the applications of advanced models to understand the behavior and performance of asphalt mixtures. It contains an introduction and five individually authored sections.

Quantifying the Mobility Effects of Winter Snow Events and the Benefits of Winter Road Maintenance

Abstract: A number of past studies have attempted to quantify the impact of winter snow events on highway mobility in terms of traffic volume, speed, and capacity. While consistent in their general findings, these studies have shown considerably different results in terms of effect size and contributing factors. More importantly, most of these efforts have not been able to capture the effects of winter maintenance operations on mobility or isolate them from those of snow event characteristics, rendering their results and the proposed methods of limited use for estimating the benefits of maintenance activities. This research attempts to address this issue through a statistical analysis of a data set that is unique in terms of spatial and temporal coverage and data completeness. The data set includes event-based observations of road weather and surface conditions, maintenance operations, traffic volume and speed, as well as several other measures from 21 highway routes over a period of three years. A matched-pair technique was employed to determine the changes in traffic volumes and speeds under matched conditions with and without snow events. A regression analysis was subsequently performed to relate the changes in traffic volume and speed over an event to various contributing factors such as highway type, snow event characteristics, and road surface conditions. A case study was conducted to illustrate the application of the developed models for quantifying the mobility impact of road surface condition and the mobility benefit of winter maintenance operations.

Tomorrow’s Forecast: Informed Drivers

Abstract: The transportation community is well on its way toward the development of wireless vehicle capabilities where vehicles communicate with other vehicles and the road infrastructure to improve safety and mobility and to reduce environmental impacts. In the near future, it will be possible for millions of vehicles to anonymously collect direct (e.g., temperature) and indirect (e.g., wiper status) measurements of the road and atmospheric conditions in their immediate surroundings. This will greatly expand the current weather observation network, particularly in respect to the roadway environment. However, the volume and anonymity of vehicle-based observations, and the fact that the observations are from a moving platform, pose several challenges related to data integrity. These must be addressed before the data will be broadly usable and acceptable. With funding and support from the U.S. Department of Transportation’s Research and Innovative Technology Administration and direction from FHWA’s Road Weather Management Program, the National Center for Atmospheric Research is conducting research to develop a vehicle data translator (VDT) to address these vehicle-based data challenges. The main function of the VDT is to quality check individual vehicle probe data elements, such as temperature and pressure, and then combine them into “derived observations” that are valid along a given length of roadway over a given time. The objective of this paper is to provide an overview of the VDT Version 3.

Diagnosing Hazardous Road Surface Conditions Through Probe Vehicle as Mobile Sensing Platform

Abstract: Harsh weather has adverse effects on traffic safety as well as on traffic flow. To mitigate the adverse effects, quick recognition of hazardous road surfaces caused by harsh weather is essential. Conventionally, Road Weather Information System (RWIS) has been used to collect road weather data. However, because RWIS can only collect spot data, not section data, the benefit could be limited, considering that road surface conditions vary dynamically even in a short roadway segment. Noting this limitation of the current RWIS, a new cost-effective approach to diagnosing hazardous road surfaces, using a probe vehicle as a mobile sensing platform was motivated in this research. The probe car equipped with a Global Positioning System receiver, a wheel speed (antilock braking system) sensor, and a G-sensor can diagnose slipperiness and roughness of a given road section. To detect slipperiness, a vehicle wheel slip ratio defined as the relative difference between vehicle body and wheel rotation speeds was used. To detect roughness, the vehicle vertical acceleration collected by the G-sensor was used. Experiments were performed under dry and wet road conditions. The slip ratios exhibited under the two conditions were significantly different. Also, it was found that the roughness caused by potholes on a rainy day can be determined on the basis of G-sensor outputs, especially when a probe car travels over a pothole.

Impact of Climate Change on Use of Anti-Icing and Deicing Salt in Sweden

Abstract: The future needs for winter maintenance will probably be influenced by the climate change in different ways in different parts of the world. As Sweden is a country with several climate zones, the influence of climate change on winter maintenance will therefore differ between regions within the country. To understand the influence of climate change on the future needs of salt consumption in winter maintenance, modeled road weather data were calculated in the IRWIN project (a joint research project through ERA-NET ROAD funded by the 6th Framework Program of the European Commission), where climate change scenarios from ECHAM5 (the fifth generation of the European Centre Hamburg Model general circulation model from the Max-Planck Institute for Meteorology) were combined with field data from the road weather information system in Sweden. These modeled road weather data were used in project KLIVIN (the study presented here) in three Swedish regions (Gothenburg, Stockholm, and Sundsvall) and was combined with the Swedish winter severity index in order to calculate the trends of future salt needs. In this study the needs of salt for each of the three investigated regions were calculated in 30-year periods between 1970 and 2100. The results show that salt use related to snowfall will decrease in all three regions, while the salt use related to temperature will increase in the northernmost region (Sundsvall) and show a small decrease in the two other regions (Gothenburg and Stockholm).

New Methods to Quality Check Road and Weather Observations for Vehicle Data

Abstract: The FHWA’s Connected Vehicle (formerly IntelliDrive) research project initiative for mobile data collection from consumer automobiles requires knowledge and trust in the quality of data coming from these vehicles. Connected Vehicle is designed to create a fully connected transportation system to provide road and weather data collection from an extensive array of vehicles. While the implementation of Connected Vehicle is in the future, some of the elements and technologies are already in place today. Since 1996, automobiles sold in the United States are required to be equipped with an Onboard Diagnostic Version 2 (OBDII) port that streams live data from sensors located onboard the vehicle. While these sensors were designed for vehicle diagnostics, some of the data can be used to determine weather characteristics around the vehicle. The OBDII data can be collected by a smartphone and sent to a server in real-time to be processed, thus providing a test bed for research into potential applications of mobile data. Some initial studies raise the question about the quality and biases from the OBDII data. Over time, effective operational techniques for stationary atmospheric sensor data have been developed; yet, no techniques exist for operational quality control of surface mobile data. Current methods of road weather data reporting have been limited to static in situ sensor stations. These road weather information systems (RWIS) provide varied data about precipitation, winds, temperature, road conditions, and more, but their siting does not always provide an accurate representation of weather and road conditions along the roadway. The use of mobile data collection from vehicles travelling the highway corridors may therefore assist in the locations where RWIS sitings are sparse or nonexistent.

Simulating Winter Maintenance for Performance Measurement

Abstract: A common problem for transportation agencies performing winter maintenance is adequately measuring the effectiveness and efficiency of winter maintenance operations. A lack of quantifiable data hinders an agency’s capability to improve the effectiveness and efficiency of winter maintenance operations. The current practice for many agencies is to use or create winter severity indices to measure whether or not the overall efficiency of maintenance operations has improved relative to historical norms. However, when deviations from historical norms are noted, it is difficult to know whether (weather-normalized) changes in resource utilization are the result of changes in maintenance efficiency and effectiveness, or limitations of the underlying winter severity index. One promising new approach is to leverage maintenance information decision support technologies being developed and deployed to support real-time winter maintenance decision making. Technologies such as the Pooled Fund Study (PFS) Maintenance Decision Support System (MDSS) can be re-tasked to simulate likely maintenance requirements (resource utilization) and expected maintenance outcomes (road conditions) on a particular maintenance route given input–observed weather conditions and maintenance resource constraints. This simulation capability, applied over an extended time, promises to provide a new understanding of the relationships between weather conditions, roadway characteristics, resource constraints, and the resulting maintenance resource utilization and road conditions. This paper will provide an overview of current efforts to apply the PFS MDSS to the problem and will include an overview of the obstacles encountered and preliminary results of the concept in several locales across the United States.

Winter Performance Measurement Using Traffic Speed Modeling

Abstract: Traffic flow is often disrupted to varying degrees during precipitation, frost, and blowing snow events. In general, as winter weather events cause road conditions to deteriorate, traffic has a tendency to slow down. Winter maintenance activities affect road conditions and therefore impact traffic speed, so a measurement system using traffic speed has the potential to be a direct measure of the impact of maintenance activities. A prototype model has been developed to predict the average traffic speed at a given time during a winter storm event using commonly reported and forecast road weather data. The prototype model has shown much promise in the quantitative evaluation of winter maintenance by comparing the simulated traffic speed at any point in time to the actual traffic speeds observed by traffic speed sensors. Winter operations may be considered successful when observed traffic speed is found to be at or above the model prediction, and operations may be considered unsuccessful when speeds are significantly less than the model predicts. The minute-by-minute nature of the model output makes it easier to evaluate the specific series of events contributing to the microscale successes or failures over the course of an event. The prototype model is being analyzed and improved for incorporation into real-time performance analysis systems.

Sustainable Winter Maintenance and a 22-in. Blizzard: Case Study

Abstract: On February 1 and 2, 2011, a particularly severe winter storm occurred across a broad swath of the United States. The storm hit the Midwest particularly hard, and areas around Chicago, Illinois, received close to 2 ft of new snow. Additionally, winds during the storm were very high, with wind speeds in excess of 50 mph not uncommon. Snowfall began on Tuesday, February 1 and for the most part had ended in the Chicago area by 9:00 a.m. on Wednesday, February 2. Many roads in the area were blocked with abandoned cars and other vehicles, and drifts in excess of 6 ft in height were not uncommon. For example, as shown in many news reports (See http://latimesblogs.latimes.com/chatter/2011/02/lake-shore-drive.html, http://www.examiner. com/community-life-in-chicago/lake-shore-drive-chicago-reopened-after-blizzard-car-claiminfo, and http://www.huffingtonpost.com/2011/02/04/chicago-blizzard-stranded_0_n_818577. html as examples), several hundred vehicles were caught in deep drifts on Lakeshore Drive in Chicago. McHenry County, Illinois, is located about 50 mi north of Chicago and received 22 in. of new snow in this storm. The County Division of Transportation has been implementing sustainable winter maintenance practices over the past several years, with a particular (although not exclusive) emphasis on limiting chemical usage. This paper reports on how McHenry County handled this storm, emphasizing how planning guided the storm response, and the end results of the activities. By 6:00 p.m. on Wednesday, February 2, all county roads were passable, and more than 70% of the lane miles were in a bare and wet condition. This makes clear that application of the principles of sustainability does not have to mean a reduced level of service for road users in winter conditions.

Study on Provision of Winter Road Snowstorm Information to Road Users

Abstract: In recent years, Hokkaido has seen traffic hazards caused by snowstorms as a result of rapidly developing low-pressure systems even in areas where, until now, the frequency of snowstorms has been relatively low. This fact highlights the importance of providing information on winter road driving environments such as snowstorm conditions, prompting appropriate responses from drivers to enhance the safety and reliability of winter roads. Thus, the authors conducted tests on providing information on winter road conditions, such as visibility during snowstorms, via personal computers (PCs) and mobile phones. The information provided in the test was as follows: (1) Information on visibility in each area of Hokkaido during a snowstorm (PCs and mobile phones); (2) Information on visibility on roads in each municipality during a snowstorm (PCs and mobile phones); (3) Information on driving time required according to the winter driving environment (only PCs); and (4) Snowstorm information on winter roads collected from road users (only PCs). An online questionnaire survey was also conducted on the effectiveness of the information on visibility in each area of Hokkaido during a snowstorm. The results showed that 90% or more respondents found the snowstorm visibility information of each Hokkaido area useful, confirming the effectiveness of the information. In addition, 80% or more respondents used the information on visibility conditions and driving time for routes in each municipality as reference for departure and arrival times, and approximately 50% referred to it for examining alternative routes. This showed the information was useful for road users to make driving plans.

Measuring Sustainability in Winter Operations

Abstract: Prior work has indicated that a useful way to consider how to make winter operations sustainable is to consider the interaction of three driving considerations: societal, environmental, and economic. Sustainable practice will be found in the region where all three considerations intersect. This approach is valuable in that it allows an agency to determine whether a given approach or operational pattern is sustainable. However, it does not readily allow for comparison between two approaches, each of which is sustainable. In other words, it does not provide a measure of the degree of sustainability for any given action. The purpose of this paper is to describe a method where sustainability of certain winter maintenance actions can be measured, specifically in context of the three considerations (societal, environmental, and economic). By way of case studies, the use of this method is demonstrated, and areas of further work are indicated.

Factors for Consideration in Selecting Snowplow Cutting Edges

Abstract: The nature of cutting edges in use in winter operations in North America has changed dramatically over the past two decades, and instead of simply being a piece of high-speed steel, today’s cutting edge is often a hybrid of multiple materials and may in fact include more than one blade all together. While cutting edges have not quite got to the level of razors, with five blades they are indisputably more complex and when used appropriately more effective than the cutting edges of old. With this complexity a challenge arises for agencies that handle winter operations: What sort of cutting edge is best? This paper approaches this challenge within the context of sustainability, acknowledging that the correct choice of cutting edge for an agency will reflect not only cost concerns but also environmental and societal issues. One benefit of this approach is that it avoids any sort of one-size-fits-all solution; because every agency faces different issues, the optimal solution should be different for each agency. In examining cutting-edge performance, two factors are obviously significant: the longevity of the cutting edge (how many miles or how many hours can it be used before it must be replaced) and the ability of a given cutting edge to remove snow from the road (how much snow or ice is left behind). These two factors in turn raise other issues. For example, the condition of the roads that the cutting edge will be used on is clearly of importance. If roads have significant ruts, then cutting edges need a heightened ability to conform to the road surface. If roads are particularly rough, then cutting edges must be very resistant to shock loading. If roads use any sort of raised pavement markings, then the cutting edges must not destroy these markings. An additional area that drives the selection of a cutting edge is the age and type of the truck fleet. A modern cutting edge can in many ways give an old plow new life. Additionally, some older vehicles may be more prone to vibration being transmitted from the cutting edge to the operator, in which case the ability of an edge to reduce vibration (and thus minimize plow noise) is an important factor. This paper describes a method where all these (and additional) behaviors can be incorporated into the cutting edge selection process. Various scenarios exhibit how this method works and show how changes in emphasis for different agencies can result in different selections.

Intelligent Transportation Systems and Support System for Winter Road Maintenance

Abstract: Using the information available within modern cars and data from road weather information systems (RWISs) makes it possible to find solutions for detection of different kinds of maintenance needs. Three models are presented: slippery road information system (SRIS), bearing information through vehicle intelligence (BiFi), and support system for winter maintenance (SSWM). The SRIS integrates information from a weather model and car data to give a view of the current condition of the road, and has shown very promising results. During the trial period, 100 cars were connected to deliver online data. The model can be used to give information to different kinds of road users, such as winter maintenance personnel and private drivers, about where there are slippery conditions as well as when it is time to lower speed limits or to perform maintenance activities. The BiFi is a model for detection of quality of the road coating and detection of bearing strength during thaw–freeze periods. The BiFi is used as a tool for judging the load-bearing capacity of the road network in a detailed and dynamic way. Tests have been successful and are a basis for further product implementation. SSWM combines information from sources such as RWIS, salt trucks, and weather forecast models, resulting in a powerful tool for winter road maintenance. The SSWM includes models for calculation of road surface temperature and road conditions, the spatial variation of slipperiness, the severity of a specific weather situation with respect to risk for road slipperiness, and need for maintenance activity.

Residual Salt and Road Surface Wetness: Comparison of Field Techniques

Abstract: Understanding the processes behind salt loss from road surfaces is of great importance if optimization of the system is to be facilitated. Salt loss has been shown to be largely dependent on road surface wetness, and this is why accurate measurements of both the salt amount and the road surface wetness are crucial to predict the future salt amount. In this paper, two field techniques for salt measurements and two field techniques for wetness measurements are compared. Both SOBO 20 and the Swedish National Road and Transport Research Institute wet dust sampler (WDS) have been shown to be suitable to measure residual salt on wet road surfaces with dissolved salt. However, when it comes to measurements of dry salt crystals, the WDS is preferred. Measuring salt that has been in solution and then dried on the road surface is also possible by both the SOBO 20 and the WDS, but the variation is larger than when measuring on wet surfaces and the measured salt amount is underestimated. The wetness of a road surface can be well established using the Wettex cloth method, but the degree of underestimation seems to be positively related to the road surface texture. The wetness comb is a very fast and easily operated method to establish the road surface wetness. The measured value is, though, strongly dependent on the road surface characteristics and illustrates why further development of the method is needed before it is recommended for field use.

Application of Collision Prediction Models for Quantifying the Safety Benefit of Winter Road Maintenance

Abstract: Winter road maintenance activities are intuitively beneficial due to their critical roles in maintaining the safety and mobility of highway networks in winter seasons. There is, however, no robust methodology currently available for quantifying these benefits. This paper introduces a set of collision risk models that have the potential to address this knowledge gap. The models were developed using a unique data set containing detailed hourly records of road weather and surface conditions, traffic counts, and collisions over 31 maintenance routes from Ontario, Canada, from 2000 to 2006. The developed models were used in several case studies to show their application for evaluating alternative winter maintenance policies and operations, such as shortening bare pavement recovery time, changing maintenance operation deployment time, and raising level of service standards.

Use of Fracture Tests and Models

Abstract: This section introduces some of the attempts made by researchers to advance testing methods that characterize the fracture properties of asphalt materials and fracture mechanics-based models that predict mixture-structural failure due to fracture in a summarized form. Meaningful answers are provided to questions such as “How do the fracture mechanics approaches work?” and “How are the fracture mechanics models applied to practical problems?” In addition, the limitations and advantages of the currently available fracture mechanics approaches (testing methods and models) that have been developed by researchers are included in the discussion.

Weather and Friction Data Collection for Winter Road Performance Evaluation

Abstract: In this project, the authors constructed a Winter Road Management System as part of technological development contributing to improvements in the efficiency, accuracy, and transparency of winter road management by providing weather forecasts, road-surface forecasts, and real-time friction data to road administrators and operators. At the same time, in this system a database linked to the data and combined with winter maintenance data and digital road maps was constructed to display the data on geographic information system maps and also to conduct winter road performance evaluation by using the accumulated data. As a result, it is possible to evaluate the judgment, results, and achievements of winter road management using more objective and transparent methods, which is expected to contribute to more efficient plan-do-check- action cycle-based management. In this report, the authors used the collected and accumulated data by the system to carry out a series of basic analyses on temporal and spatial changes in winter road performance as a function of meteorological variation and road characteristics, with a case study on the 45-km section of National Highway 230 in the Sapporo area. This paper describes a summary of the system development to date, the usability of accumulated data for winter performance evaluation, and future prospects to promote more effective and efficient winter road management.

Recent Trends in Changes in Snowfall and Snow Depth in Japan and Their Impact on Snow Control Measures

Abstract: Recently, cold snowy regions of Japan have occasionally seen trends of lighter snowfall due to warm winters, heavy snow in areas that previously had little snowfall, very heavy localized snowfall, and other unusual snowfall patterns. It is considered important for the snow and ice control to understand the climate change-related metamorphosis of snow and ice environments to enable contribution to the development of long-term snow and ice-control plans and measures. Accordingly, in this study, trends of change in snowfall and snow cover over the last 26 years were surveyed using past data. The items surveyed were seasonal maximum snow depth; accumulated seasonal snowfall; maximum 24-, 48-, and 72-h snowfall from the onset of snowfall; the frequency of days with snowfall totaling 30 cm or more; and the number of days with continuous snow cover in winter. The collected results revealed that the annual maximum depth of snow cover and the number of days with snowfall totaling 30 cm or more were on the rise in eastern Hokkaido, where it faces the Sea of Okhotsk and the Pacific Ocean. In general, this region is considered to have little snowfall as long as stable winter pressure patterns continue, while snowfall increases when low pressure develops over the Pacific Ocean and the Sea of Okhotsk. It was clarified that there were changes in snowfall patterns and in the distribution of areas with heavy snowfall.

Geospatial Weather Decision Support for Transportation Applications

Abstract: Weather is a major factor in surface transportation: it impacts traffic flow and patterns, and is often a precursor to accidents, a significant portion of which cause injury or death. Integration of current and forecast weather information into intelligent transportation system (ITS) applications, including 511 systems, can provide transportation managers with the information they need to make better decisions and provide alerts that can reduce congestion while improving safety. Improved routing, logistics coordination, maintenance operations, and efficiencies for the transport of materials can also be gained through a better understanding of weather issues that affect the transportation network. The merge of weather information with geographic information system (GIS) technology provides new and exciting capabilities now being realized by the transportation industry to mitigate weather-related risks through operational decision support. Telvent DTN has developed unique capabilities to merge weather information with non-weather assets, both stationary and mobile, to provide unparalleled weather risk monitoring and location-based alerting. Weather parameters that are relevant to specific business requirements are continuously monitored and compared to customer asset locations. Automated alerts are generated when critical weather thresholds are exceeded at the identified asset locations. These real-time location-based alerts can provide dramatically enhanced public safety, improved logistics support, and provide a superior advantage in operating business efficiencies relating to weather conditions. This advanced capability provides effective, accurate, and precise weather decision support for varied transportation applications. Covered in this paper will be the methodology, data sets (both stationary and mobile), and benefits behind this geospatial decision support for various transportation applications. Also included will be a demonstration of how this technology was utilized in conjunction with roadway weather information system (RWIS) information from Clarus in the 511NY traveler information system.