Montana Department Of Transportation Research Articles

Investigating Road Ice Formation Mechanisms Using Road Weather Information System (RWIS) Observations

Ice formation on roads leads to a higher incidence of accidents and increases winter de-icing/anti-icing costs. This study analyzed 3 years (2019–2021) of Road Weather Information System (RWIS) sub-hourly measurements collected by the Montana Department of Transportation (MDT) to understand the first-order factors of road ice formation and its mechanisms. First, road ice is formed only when the road pavement surface temperature is equal to or below the freezing point (i.e., 32 °F (i.e., 0 °C)), while the corresponding 2 m air temperature could be above 32 °F. Nevertheless, when the road pavement was below 32 °F ice often did not form on the roads. Therefore, one challenge is to know under what conditions road ice forms. Second, the pavement surface temperature is critical for road ice formation. The clear road (i.e., with no ice or snow) surface pavement temperature is generally warmer than the air temperature during both day and night. This feature is different from a natural land surface, where the land skin temperature is lower than the air temperature on cloud-free nights due to radiative cooling. Third, subsurface temperature, measured using a RWIS subsurface sensor below a road surface, did not vary as much as the pavement temperature and, thus, may not be a good index for road ice formation. Fourth, urban heat island effects lead to black ice formation more frequently than roads located in other regions. Fifth, evaporative cooling from the water surface near a road segment further reduces the outlying air temperature, a mechanism that increases heat loss for bridges or lake-side roads in addition to radiative cooling. Additionally, mechanical lifting via mountains and hills is also an efficient mechanism that makes the air condense and, consequently, form ice on the roads. Forecasting road ice formation is in high demand for road safety. These observed features may help to develop a road ice physical model consisting of functions of hyper-local weather conditions, local domain knowledge, the road texture, and geographical environment.

Making Heritage Through Montana’s Official State Highway Maps, 1914–2000*

We assess Montana highway maps produced between 1914 and 2000 to identify how the Montana Department of Transportation and its predecessors used maps to frame Montana’s place identity and heritage for promotional purposes in the twentieth century. After 1934, we document how Montana’s official state maps became a key source and shaper of tourist knowledge about the state, its history, and its attractions. Five persistent map themes—territorial identity, mythic West, natural wealth, outdoor recreation, and hospitality—are used to define Montana landscapes and heritage and to shape perceptions of the state. The normative and persuasive powers of Montana highway maps reveal them as premiere examples of a portable and place‐defining affective technology used to promote tourism within the twentieth‐century American West.

Determining Causal Factors of Severe Crashes on the Fort Peck Indian Reservation, Montana

Indian reservations have been struggling with the highest rate of crashes that lead to fatal and incapacitating injuries across the United States for decades. The US government has been striving to improve roadway safety on Indian reservations to reduce such crashes. However, the rustic nature of the reservations, issues of jurisdictional coordination and collaboration, inadequate resources, and limited crash data make it challenging for the tribes to reduce the number of severe crashes. Determining factors associated with crashes is one of the most efficient and effective ways to select appropriate countermeasures for improving roadway safety and reducing crashes. Due to the unique nature of each of the reservations, factors contributing to crashes vary across the reservations as well as across the different roadways within the reservations. Only a few researches have investigated factors contributing to crashes on Indian reservations, and no studies have determined the factors separately for different roadways within the reservations. Therefore, this study was conducted to identify the contributory factors to fatal and injury crashes in the Fort Peck Indian Reservation (FPIR). The crash database covering a ten-year period from 2005 to 2014 was obtained from the Montana Department of Transportation (MDT). During this period, 940 crashes occurred on state, county, city, and tribally owned roads. Binary logistic regression models were developed to determine the factors associated with fatal and injury crashes for all roads within the FPIR and separately for the roads maintained by different agencies. The analysis identified unique contributory factors to fatal or injury crashes for different roadways, which justified separating crashes based on different road types. Impaired driving, adverse weather condition, collision with a ditch/embankment, pedestrian involvement, and overturn/rollover crashes were some of the factors that significantly contribute to increasing the risk associated with fatal and injury crashes. Impaired driving was found to be the most significant factor contributing to crash severity in all three roadways. Indian reservation roads were found to be possessing the highest risk of fatal and injury crashes due to impaired driving among the three roadway systems. The results of the study provide the Fort Peck Tribes with the opportunity to determine the countermeasures for safety improvements on their roadway systems efficiently.

Estimating Event Likelihood for Rock Slope Assets on Transportation Networks

Recent federal regulations require states to develop risk-based transportation asset management (TAM) plans for bridge and pavement assets. These requirements are making TAM principles, and their related benefits and tools, familiar to a variety of sections within Departments of Transportation (DOTs) and prompting select DOTs to apply them to select geotechnical assets. The Montana Department of Transportation (MDT) recently completed a multi-year project to update its previous Rockfall Hazard Rating System (RHRS) into a Rock slope Asset Management Program (RAMP), incorporating some of these new tools. Incorporating risk into decision-making is important, but risk posed by deteriorating geotechnical assets is difficult for departments to quantify. Adverse event data are often collected in an ad-hoc fashion, with only the worst events attracting attention. As part of the RAMP project, an MDT-administered adverse event survey was combined with a statewide dataset of detailed rock slope assessments. These data were used to develop initial relationships between rock slope condition and adverse event likelihood per unit area of rock slope face. Annual likelihood of both service disrupting events and accidents was calculated for each rock slope in MDT’s database and used to identify high-risk corridors. Using established AASHTO methods, event likelihood was combined with traffic and detour data, generating site-specific estimates of annual safety and mobility risks, expressed in dollars, which can be incorporated into benefit/cost tools at various planning levels and permits dollar-to-dollar comparisons of the risks posed by rock slope assets to other actively managed assets.

A quantitative approach to assessing the efficacy of occupant protection programs: A case study from Montana

Quantitative evaluation of vehicle occupant protection programs is critical for ensuring efficient government resource allocation, but few methods exist for conducting evaluation across multiple programs simultaneously. Here we present an analysis of occupant protection efficacy in the state of Montana. This approach relies on seat belt compliance rates as measured by the National Occupant Protection Usage Survey (NOPUS). A hierarchical logistic regression model is used to estimate the impacts of four Montana Department of Transportation (MDT)-funded occupant protection programs used in the state of Montana, following adjustment for a suite of potential confounders. Activity from two programs, Buckle Up coalitions and media campaigns, are associated with increased seat belt use in Montana, whereas the impact of another program, Selective Traffic Enforcement, is potentially masked by other program activity. A final program, Driver’s Education, is not associated with any shift in seat belt use. This method allows for a preliminary quantitative estimation of program impacts without requiring states to obtain any new seat belt use data. This approach provides states a preliminary look at program impacts, and a means for carefully planning future program allocation and investigation.

Libby North Corridor Study

The Montana Department of Transportation (MDT) developed the corridor-planning process to bridge the gap between its statewide long-range transportation policy plan and project-level National Environmental Policy Act (NEPA) processes. MDT cooperated with Lincoln County, Montana; the USDA Forest Service; and FHWA to complete the Libby North Corridor Study. The approach used new rules and regulations: 23 Code of Federal Regulations, Part 450, Appendix A: Linking the Transportation Planning and NEPA Processes. Corridor planning complements NEPA and ensures that decisions are made at the appropriate level with consideration of low-cost alternatives and available funding. Environmentally complex issues in the Pipe Creek area, north of Libby, prompted the study. It was uncertain whether any project was possible on this secondary highway (MT-567) because of its environmentally challenging location: parallel to Pipe Creek (Bull Trout Critical Habitat), within the Kootenai National Forest and grizzly bear habitat distribution area, and just outside the Cabinet–Yaak grizzly bear recovery zone. If this project had been developed under traditional methods beginning with the NEPA-compliant environmental review, a full environmental impact study would have been likely. Concerned that any reconstruction would be insurmountable and not fundable because of environmental sensitivities, MDT and the county took a step back. The corridor was reassessed at the planning level to obtain a better understanding of corridor limitations and needs and to determine what improvements, if any, could be pursued. With the aid of many stakeholders and agencies, the study identified recommendations for improving safety, maintaining the scenic character of the corridor, and minimizing impacts to threatened and endangered species.

Limited Amendment Process of Montana's Statewide Long-Range Transportation Plan to Meet SAFETEA-LU Requirements

The Montana Department of Transportation (MDT) uses a limited process to amend its statewide transportation plan and bring it into compliance with the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) regulations. This amendment process is an alternative to a full-scale, long-range transportation plan update. An overview is presented of ongoing business and planning processes that have made this limited amendment possible, followed by discussion about the approach used in Montana. The discussion focuses on specific areas addressed by the limited amendment process, including efficient management of the transportation system, economic development and land use planning, environmental mitigation, safety, and new consultations. Existing processes addressing such areas were in place before the amendment, including the performance programming process, the highway economic analysis tool, and the corridor planning process. The policy basis for these processes was established in earlier statewide transportation policy plans, whereas the specific business processes used evolved over several years. Limited amendments support maturing statewide planning processes because the mechanisms used for initial full-scale plans, once established within a state department of transportation, can become the drivers behind planning processes that advance either opportunistically or as evolutionary business process change. Some of these mechanisms are continuous robust public involvement, routine cyclic strategic environmental scans, and ongoing fiscal and technical analysis.

Preservation of Infrastructure by Using Weigh-in-Motion Coordinated Weight Enforcement

The Montana Department of Transportation (DOT) has completed a pilot project in which data from a statewide network of weigh-in-motion (WIM) sensors were used to assist in scheduling weight-enforcement activities of patrol personnel. The purpose of the project was to determine if one of the division’s objectives—reducing infrastructure damage from overweight vehicles—could be better realized by using WIM data when dispatching officers. Data for the project were obtained from Montana’s state truck activities reporting system (STARS), which consists of WIM sites deployed around the state to collect information for a spectrum of Montana DOT activities. In this case, the STARS data were processed to determine the pavement damage caused by overweight vehicles each month during the baseline year. The trends identified from this analysis were used in the subsequent year to direct patrol efforts each month to the five sites that historically had experienced the greatest pavement damage from overweight vehicles. Officers were directed to the specific vehicle configurations historically responsible for the damage, as well as to their direction of travel and time of operation. During this year of WIM-directed enforcement, pavement damage from overweight vehicles decreased by 4.8 million equivalent single-axle load miles, and the percentage of vehicles operating over weight decreased by 20% across all STARS sites (both enforced and unenforced). While changes in loading patterns were observed during the enforcement activities (fewer overweight and more weight-compliant vehicles), the effectiveness of the focused enforcement in producing long-term changes in loading behaviors was uncertain.

Performance Programming: Guiding Resource Allocation to Achieve Policy Objectives

The Montana Department of Transportation’s (MDT) performance programming process (P3) is defined as “a method to develop an optimal investment plan and measure progress in moving toward strategic transportation system goals.” Transportation goals are based on the policy directions defined in the statewide long–range transportation plan. The distribution of funding is established through a series of trade-off analyses based on analyzing how the program can best meet overall performance goals. P3 allows system performance to be tracked over time and for various policy options to be systematically analyzed. In addition, P3 commits projects to the Statewide Transportation Improvement Program, whose contribution to system performance was estimated through an analytical process. A case study of the MDT process is provided. The Montana context that led to the development of P3 and the key steps of P3 are described, and the impact of the process on MDT decision making is explained. A discussion of implementation issues and next steps in MDT’s incremental implementation of this process is provided.

Seasonal Variation of Moisture and Subsurface Layer Moduli

In 1995 the Montana Department of Transportation initiated a study on the seasonal variation of pavement strength, with an emphasis on spring thawing. Ten sites representing a cross section of Montana subgrade soil and pavement structure were selected and instrumented with moisture and temperature sensors. Field measurements of surface deflections, moistures, and temperatures were initiated in autumn 1996 and continued through the spring of 1997. The moisture and deflection data were used to determine the thaw-weakening characteristics of the sites and to develop subgrade modulus values for use in the future design of pavement structures using AASHTO mechanistic design methodology. Results indicated that in several areas not only the subgrade but also the base course layers were prone to thaw weakening. The length of thaw weakening varied from 4 days to a 3-week period. In addition, it was found that in almost all cases the subsurface moisture content began to increase rapidly when the subsurface temperature rose to around–2°C during the spring. In some cases it was found that when the subsurface temperature finally warmed to 0°C, the moisture content had reached its prefreeze value. This research provides a general description of the test sites and measurements; it quantifies the effects of thaw weakening on typical roads in Montana based on deflection and surface and subsurface moisture and temperature.

Montana’s Automated Deflection Analysis Procedure

Economic conditions in the state of Montana during the past few years have dictated that the time and cost required to collect and analyze deflection data be significantly reduced. Consequently, the Montana Department of Transportation (MDT) undertook the development of an automated deflection analysis procedure (ADAP). This effort resulted in a PC-based Microsoft Windows application that provides a single program to assist the user in each step of the backcalculation analyses, from raw data to generated reports. The ADAP system consists of three components: preprocessor, main processor, and postprocessor. The preprocessor is used to import, validate, and extract deflection data and other pertinent pavement information from the Road Rater and MDT Oracle data base files and to generate the input for the MODULUS backcalculation program. The MODULUS program, which is the main system processor, is used to backcalculate in situ pavement layer moduli. The postprocessor provides the ability to generate reports and retrieve the analysis results, calculate the structural capacity and remaining life of the pavements in question, and upload the results to the MDT Oracle data base. In addition to providing for a more consistent, productive, and straightforward backcalculation process, the time and resources to perform the analysis of deflection data have been significantly reduced. Initial estimates indicate that instead of the 3 to 4 hr of work that were required for every hour of data collection, only 1 hr is now required, and this time will likely decrease as the MDT staff becomes more familiar with the program.