Promothes Saha

Network Model for Rural Roadway Tolling with Pavement Deterioration and Repair

A rural pricing model which calculates diversion endogenously with a network assignment model is described in the article. Roadway tolling is often tied to revenue generation for roadway maintenance in rural areas and rural pricing models should directly incorporate a pavement deterioration and maintenance model. However, the interactions between these models are not simple, because tolls cause traffic diversion, which in turn affects deterioration rates and forecasted revenue. The pricing model presented in this article captures deterioration rates and pavement condition in the toll-setters objective function, which maximizes long-run net present value of the highway infrastructure. A demonstration is made using a network that represents the state of Wyoming (28 zones, 60 nodes, and 188 links). A novel deterioration model is used which is particularly suitable for computational efficiency and the resulting model is discontinuous and nondifferentiable and involves solving a knapsack problem as a subproblem. Therefore, a simulated annealing-based algorithm is presented to solve it, in the framework of a new solution method built upon partitioning the feasible region. Sensitivity analyses reveal that although the locations for optimal tolling are relatively stable as demand changes, the revenue collected can substantially vary. Future research should investigate strategies for incorporating more advanced pavement network models. This paper used simple models for computational reasons.

Safety Effectiveness of Variable Speed Limit System in Adverse Weather Conditions on Challenging Roadway Geometry

This paper examined the interaction between roadway geometric characteristics and adverse weather conditions and their impact on crash occurrence on rural variable speed limit freeway corridors through mountainous terrain. As a quantitative measure of the effect of geometrics in adverse weather conditions, a crash frequency safety performance function that used generalized linear regression was developed with explanatory variables including snow, ice, frost, wind, horizontal curvature, and steep grades. This research concluded that the interaction between grades and horizontal curves with weather variables had a significant impact on crash occurrence. The research suggested that distinct variable speed limit strategies should be implemented on segments with challenging roadway geometry.

A risk-based optimisation methodology for pavement management system of county roads

A pavement management system (PMS) is a strategic and systematic process to maintain and upgrade the road network. When funding is limited, it is very important to identify the best mix of road preservation projects that provides the maximum benefits to society in terms of overall life cycle cost of the road network. The most common factors that play an important role for identifying projects are the following: budget, traffic volume, Present Serviceability Index (PSI) and risk associated with selecting treatment types. This research develops an optimisation methodology for county paved roads that identify the best mix of preservation projects within budget, maximising traffic (passengers and trucks traffic) on treated roads, maximising the weighted average PSI, and minimising the risk. This methodology will facilitate a statewide implementation of PMS for counties in the state of Wyoming.

Impact of traffic Enforcement on Traffic Safety

Motor vehicle crashes (MVCs) have a huge cost to society in terms of death, injury and property damage. The cost of fatal MVCs alone is estimated at US

Developing performance models for treated gravel roads to evaluate the cost-effectiveness of using dust chemical treatments

44 billion per year. Among many confounding factors, traffic citations as an element that may reduce MVC frequency are not well understood, and most research carried out to date has evaluated the effects of the total number of citations on the number of MVCs. However, certain types of citations may be more likely to reduce the number of MVCs, whereas other types are not very effective. This research was set out to examine the impact of different types of traffic citations on MVCs on two hazardous main US highways in Wyoming US-30 and US-26. A negative binomial modeling technique was implemented by exploiting 4 years of crash and citations data to identify the causal impacts of traffic citations on crash frequency by incorporating traffic and geometric features. The modeling results showed that higher numbers of speeding and seat belt citations reduce the number of crashes significantly. These findings are the results of law enforcement efforts along the highways. Traffic count and the number of horizontal curves were found to significantly increase the number of MVCs.

Developing Pavement Distress Deterioration Models for Pavement Management System Using Markovian Probabilistic Process

Abstract The objective of this study is to develop a long-term performance model to predict the service life of treated gravel roads. Fugitive dust emissions from 11 recently treated gravel roads located in five different counties in the state of Wyoming were measured periodically for 12 months. Visual survey ratings of the 11 roads were taken each time. Surfacing moisture samples were collected. Traffic speeds and volumes by class were also collected using a two-tube traffic counting system. Surfacing aggregate samples were collected and their gradations were determined. Performance curves were developed for each of the selected 11 roads. A comprehensive long-term performance model was developed that predicts the service life of treatment on gravel roads. A life cycle cost analysis comparison study was also conducted to compare the cost of maintaining untreated gravel roads with the cost of maintaining treated gravel roads. Statistical analyses generated regression models that allowed the prediction of factors significant to the service life of treatment on gravel roads. It was found that the daily traffic, the percentage of fines in the soil and the annual rainfall had the highest contribution to road deteriorations and increase in dust generation. Dust treatment was found to have a service life of one year before dust emission rates went back to before treatment levels. The life cycle cost analysis indicates that the initial cost of applying dust suppressant treatment to gravel roads is expensive. However, it will increase the road service life and significantly reduce dust generation.

Development of serviceability prediction model for county paved roads

In the state of Colorado, the Colorado Department of Transportation (CDOT) utilizes their pavement management system (PMS) to manage approximately 9,100 miles of interstate, highways, and low-volume roads. Three types of deterioration models are currently being used in the existing PMS: site-specific, family, and expert opinion curves. These curves are developed using deterministic techniques. In the deterministic technique, the uncertainties of pavement deterioration related to traffic and weather are not considered. Probabilistic models that take into account the uncertainties result in more accurate curves. In this study, probabilistic models using the discrete-time Markov process were developed for five distress indices: transverse, longitudinal, fatigue, rut, and ride indices, as a case study on low-volume roads. Regression techniques were used to develop the deterioration paths using the predicted distribution of indices estimated from the Markov process. Results indicated that longitudinal, fatigue, and rut indices had very slow deterioration over time, whereas transverse and ride indices showed faster deterioration. The developed deterioration models had the coefficient of determination (R2) above 0.84. As probabilistic models provide more accurate results, it is recommended that these models be used as the family curves in the CDOT PMS for low-volume roads.

Impact of traffic citations to reduce truck crashes on challenging roadway geometry

Abstract This paper developed a pavement serviceability prediction model for county paved roads. Most county paved roads were built decades ago without following minimum design standards. The recent increase in industrial/mineral activities in the State of Wyoming required developing a pavement management system (PMS) for local paved roads. The developed PMS used the pavement serviceability index (PSI) as a pavement performance parameter. The proposed PSI model for local roads is based on: international roughness index, pavement condition index (PCI) and rut depth for flexible pavements only. Ten panellists from Wyoming rated 30 pavement sections that were randomly selected at different distresses’ levels; using two vehicles (SUV and Sedan). The statistical analysis indicated that the seating position, age and gender are not significant to the rating process. However, the vehicle’s type found to be significant. The newly developed model from this study explains 80% of the variations in the PSI values of county roads (adjusted R2 = 0.80). In addition, the new model seems to provide more realistic representation of the conditions of county roads than the statewide model used on the state’s highway system.

Developing an Optimization Model to Manage Unpaved Roads

ABSTRACT Wyomings Interstate 80 has one of the highest truck crash rates in the United States. This is due to a variety of reasons, including high percentage of truck traffic, adverse weather conditions and mountainous terrain. These factors have caused the Wyoming Highway Patrol (WHP) to spend extensive resources on inspecting commercial vehicles and enforcement of traffic laws in this corridor. This study estimated the correlation between traffic citations and truck crashes. In addition, the paper evaluated the increased risk of truck crashes in adverse weather and road conditions. The explanatory variables included geometric features, weather condition, traffic volume and types of citations. This research concluded that speeding related citations and truck crashes are negatively correlated, and the risk of truck crashes is significantly higher when weather is not clear, and the road is not dry.

Truck safety evaluation on Wyoming mountain passes

While approximately two-thirds of the total centerline miles are unpaved in the state of Wyoming, there is no optimization program for managing these roads. Unlike paved roads, unpaved roads deteriorate from excellent to failed conditions in sometimes less than a year. This deterioration rate necessitates developing a novel methodology for managing them efficiently. When funding is limited, it is important to identify the best mix of road preservation projects that provides the most benefits to society in terms of overall life cycle cost of the road network. This research intends to develop a management system using optimization techniques for managing unpaved roads within limited budget. The common factors that play the most important role for identifying projects are road condition parameters, unpaved road deterioration model, treatment types, cost-factors associated with selecting treatment types, traffic counts, budget, and treatment cost. Road condition parameters include cross section, roadside drainage, rutting, potholes, loose aggregate, dust, corrugation, and ride quality. This methodology will facilitate a statewide implementation of unpaved road management system for counties in Wyoming. The methodology can be easily adopted by other states interested in the management of gravel roads.