Zhirui Ye

Safety Effects of Winter Weather: The State of Knowledge and Remaining Challenges

Abstract In recent years, there has been growing recognition of the effects of weather on the surface transportation system. Although considerable work has been done in quantifying the effects of weather on the highway system, there is still much that remains unknown about the relationship between weather and highway system performance. This paper synthesizes the findings from some of the major efforts in this area. The review of existing studies found consistent patterns that adverse weather reduces traffic speed and increases crash frequencies, while fatal crashes are decreased. A table is then presented which estimates the change in crash frequency and vehicle travel speed resulting from various winter weather conditions, based on a synthesis of earlier work. To estimate the safety and speed adjustment factors of compacted snow, a severity index is also developed. Recognizing the lack of comparability between the results of the studies, the paper concludes with a detailed discussion of avenues for future research which could help to address some of the gaps which currently exist. These challenges include, but are no limited to: quantification of the dynamic layer, development of the relationship between pavement friction and the composition of the dynamic layer, evaluation of the effects of pavement friction on vehicle speed, and evaluation of safety effects of weather conditions above the pavement.

Evaluation of Effects of Weather Information on Winter Maintenance Costs

The objective of this study is to investigate and evaluate the effects of weather information (in terms of accuracy and frequency of usage) on winter maintenance costs. To this end, a general winter maintenance cost model is presented, and then a methodology combining sensitivity analysis and neural network methods is proposed. Sensitivity analysis is used to identify the key input variables that significantly affect the output variable. The proposed method and cost model are applied to a case study of the Iowa winter maintenance operations. The results from the case study show that the lane miles of roadway maintained by maintenance units have the most important impact on winter maintenance costs; also, the increased use and accuracy of weather information can reduce costs. Finally, a benefit–cost analysis shows that the use of accurate weather information is a promising way to reduce winter maintenance costs.

Benefit-Cost Analysis of Maintenance Decision Support System

The pooled fund study of the Maintenance Decision Support System (MDSS), led by South Dakota and now including 13 state departments of transportation, developed an operational MDSS for winter maintenance. While the MDSS is generally perceived to be beneficial, it is important to determine more formally the tangible benefits and costs associated with its implementation and to determine whether it is a good investment. This paper presents the results of a benefit–cost analysis of the pooled fund MDSS. The development of the analysis method includes the identification of benefits and costs, the definition of base case and alternatives, and the development of a benefit–cost model. A base case (without MDSS) and two other alternatives (with MDSS) are defined for the analysis. The developed method consists of two parallel modules: a baseline data module and a simulation module. Results from a case study applying this method show that the implementation of MDSS brings more benefits than costs.

Evaluating Snow and Ice Control Chemicals for Environmentally Sustainable Highway Maintenance Operations

AbstractThe use of chemicals and abrasives for highway winter maintenance operations is an essential strategy for ensuring a reasonably high level of service, yet the performance of such materials has to be balanced with their potential negative impacts on motor vehicles, transportation infrastructure, and the natural environment. In this context, this work presents a comprehensive and quantitative evaluation of snow and ice control chemicals currently used by various Idaho Transportation Department districts for highway maintenance operations, including rock salts (mainly solid sodium chloride), IceSlicer products (solid sodium chloride with trace amounts of other chlorides), and salt brines. The analysis has been enabled by the utilization of existing lab and field test data along with reasonable assumptions, in the effort to identify environmentally sustainable materials for winter highway operations. Despite its caveats, this case study is the first attempt to incorporate the most up-to-date informati...

Estimating Statewide Benefits of Winter Maintenance Operations

Winter highway maintenance activities offer direct and indirect benefits to the public. However, the cost of such activities is such a major outlay that it demands close scrutiny. There is a need to understand better and quantitatively estimate the benefits of winter road maintenance. Therefore, the work discussed in this paper was undertaken to quantitatively assess the benefits of winter highway operations at the state level. Methodologies were developed to estimate the major benefits of winter maintenance, including safety improvements, travel time savings, and fuel savings. A Minnesota case was used to demonstrate the methodologies and quantify those benefits. Results of the case study showed the benefits of winter highway maintenance by the Minnesota Department of Transportation to be

Empirical investigation on safety constraints of merging pedestrian crowd through macroscopic and microscopic analysis

227 million per winter season, with

Costs and Benefits of Tools to Maintain Winter Roads: A Renewed Perspective Based on Recent Research

168 million of safety benefits,

Evaluation of Winter Maintenance Chemicals and Crashes with an Artificial Neural Network

11 million of mobility benefits, and

Traffic Management of Special Events in Small Communities

48 million of fuel savings. The benefit–cost ratio of winter highway operations in Minnesota was 6.2, in which material costs were taken into account.

A review of experimental studies on complex pedestrian movement behaviors

A recent crowd stampede during a New Years Eve celebration in Shanghai, China resulted in 36 fatalities and over 49 serious injuries. Many of such tragic crowd accidents around the world resulted from complex multi-direction crowd movement such as merging behavior. Although there are a few studies on merging crowd behavior, none of them have conducted a systematic analysis considering the impact of both merging angle and flow direction towards the safety of pedestrian crowd movement. In this study, a series of controlled laboratory experiments were conducted to examine the safety constraints of merging pedestrian crowd movements considering merging angle (60°, 90° and 180°) and flow direction under slow running and blocked vision condition. Then, macroscopic and microscopic properties of crowd dynamics are obtained and visualized through the analysis of pedestrian crowd trajectory data derived from video footage. It was found that merging angle had a significant influence on the fluctuations of pedestrian flows, which is important in a critical situation such as emergency evacuation. As the merging angle increased, mean velocity and mean flow at the measuring region in the exit corridors decreased, while mean density increased. A similar trend was observed for the number of weaving and overtaking conflicts, which resulted in the increase of mean headway. Further, flow direction had a significant impact on the outflow of the individuals while blocked vision had an influence on pedestrian crowd interactions and merging process. Finally, this paper discusses safety assessments on crowd merging behaviors along with some recommendations for future research. Findings from this study can assist in the development and validation of pedestrian crowd simulation models as well as organization and control of crowd events.