The Virginia Department of Transportation’s (VDOT) first performance-based road-maintenance contract was concluded in July 2007. This contract required the contractor to maintain all assets and carry out incident management and snow and ice removal services on a total of 250 mi (402 km) of a number of Virginia’s interstate highways. This contract acted as a pilot project for VDOT and other states departments of transportation (DOT). Since performance-based road-maintenance contracting is rather new and yet to be utilized by many state DOTs, there is an emerging need to (1) assess whether its use is viable, and (2) inform the state DOTs of the key issues to consider when using performance-based road-maintenance contracting. The purpose of this paper is to address this need by providing a comprehensive evaluation of VDOT’s overall experience with its pilot performance-based road-maintenance contract. The findings from the analyses over a period of 6 years indicate that while meeting or coming very close to the performance targets most of the time, there have been years in which the contractor was not able to meet performance targets in fence-to-fence asset groups and bridges. As far as the comparison of the level-of-service effectiveness performance of the contractor with that of VDOT utilizing traditional maintenance approaches is concerned, our findings show that the contractor outperformed VDOT in fence-to-fence asset groups. The key issues that a state DOT should consider when using performance-based road-maintenance contracting, as learned from VDOT’s pilot project experience, can be summarized as (1) tying payments to be made to the contractor to actual performance, (2) generating a detailed baseline condition information, (3) using performance targets that increase (as opposed to being constant) over the contract period, (4) establishing a performance target for every single item required to be maintained, (5) having multiple inspections per year, (6) developing a standard rating procedure for all elements, and (7) developing objective, quantifiable, and easily measurable performance criteria.

A key to the use of weigh-in-motion (WIM) traffic data for the Mechanistic-Empirical Pavement Design Guide (MEPDG) is to be able to successfully recognize the differences in loading patterns and to estimate the full axle-load spectrum data occurring under different conditions. However, how to identify these patterns on the basis of the large amount of WIM data remains a challenge. In this paper, WIM data collected in the state of Arkansas are analyzed by using cluster analysis methodologies to identify groups of WIM sites with similar traffic characteristics on the basis of the MEPDG-required traffic attributes. Case studies are presented and the cluster results are discussed. Combining the loading clusters, four long-term transportation planning factors currently adopted in Arkansas, including the modified Arkansas primary highway network (APHN) classification, demography, geography, and region attribute (rural or urban) of a highway under design, are adopted as the influencing criteria to develop the truck loading groups. The most significant influencing criteria are identified by using Fisher’s exact test. Consequently, truck loading groups and their categorical logit models are developed in the paper. The developed method for determining truck loading groups will simplify the understanding and applicability of the traffic patterns and ultimately ease the preparation of the traffic load spectra inputs on the basis of WIM data for the MEPDG procedure.

Many research studies and field experiences have shown a strong relationship between wet-weather accidents and pavement skid resistance. Therefore, measurement methods and models are needed to evaluate the safety level of driving on an asphalt pavement surface during its service life. The objective of this study was to develop a skid resistance prediction model based on measurable quantities such as aggregate shape characteristics, aggregate gradation, aggregate resistance to polishing, and traffic level. To achieve this objective, the skid number (SN) of asphalt pavement sections and traffic data were acquired and analyzed. In addition, statistical analysis was conducted to determine the relationship between different aggregate properties, pavement surface characteristics, and the measured SN values. The aggregate properties were measured using conventional test methods (acid insolubility, magnesium soundness, micro-Deval, and British polish value), and the Aggregate Imaging System (AIMS). The pavement surface characteristics were measured using the dynamic friction tester and circular texture meter. The statistical analysis led to the development of a new model for predicting the asphalt pavement SN as a function of traffic level, initial and terminal aggregate texture values measured using AIMS, and aggregate gradation described using the two-parameter Weibull distribution function.

The development of bituminous binders with an intrinsic fuel resistance is required to limit pavement damage and maintenance operations in those areas, such as airport systems and industrial areas and filling stations, where the risk of fuel spilling exists. This paper focuses on the study of the interactions between bitumen and fuel to attain a composition of modified binders with enhanced fuel resistance. Several different modifiers, including polymeric materials, recycled crumb rubber, and synthetic waxes, were added to a base bitumen. All blends were studied with special reference to their chemical composition and subjected to a solubility test consisting of a controlled immersion in kerosene (jet fuel A-1). The results were interpreted on the basis of the compositional characteristics which determine the interactions occurring between bitumen and modifiers. Among the formulations with enhanced fuel resistance, those based on synthetic waxes appeared to be the most interesting ones.

Steel-fiber reinforced concrete (SFRC) brings favorable properties to concrete ground slabs. The use of the material is limited by the lack of an appropriate analysis method. This paper is the first in a series of two regarding research aimed at providing a modeling approach that can be used to model the behavior of SFRC concrete and SFRC ground slabs. Here, an improved generalized analytical method is presented to determine the tensile stress-strain ($\sigma \mathrm{\text{-}}\epsilon$) response using an inverse analysis. The tensile $\sigma \mathrm{\text{-}}\epsilon$ response is determined by using either the experimental moment-curvature ($M\mathrm{\text{-}}\varphi$) or load-deflection ($P\mathrm{\text{-}}\delta$) responses. The validity of the inverse analysis is evaluated by comparing calculated and measured tensile $\sigma \mathrm{\text{-}}\epsilon$ responses. The tensile $\sigma \mathrm{\text{-}}\epsilon$ response is subsequently utilized in nonlinear finite-element analysis of an SFRC beam with the purpose of examining the tensile $\sigma \mathrm{\text{-}}\epsilon$ relationship. The calculated results compare well with the experimental observations.

Steel-fiber reinforced concrete (SFRC) brings favorable properties to concrete pavements. The use of the material is limited by the lack of an appropriate analysis method. This paper is the second in a series of two aimed at providing a modeling approach, which can be used to model the behavior of SFRC concrete and SFRC ground slabs. In this paper, a finite-element model, capable of simulating the nonlinear behavior of the SFRC slab, is proposed and compared with the slab’s experimental response. An approximate model describing the behavior of the support layers is developed using results from a plate-bearing test. The same support model is adopted for the analysis of the combined structure of the slab and the support. The material model developed and tested in the first paper, for the SFRC containing $15\mathrm{kg}/{\mathrm{m}}^3$ of steel fiber, is adopted for the analysis of the SFRC slabs. In addition, a parameter study is conducted to investigate the influence of concrete strength, steel-fiber content, and the support stiffness on the load displacement ($P–\Delta$) response of SFRC ground slabs.

This paper demonstrates an innovative reliability analysis approach for prediction of asphalt rutting performance. In this approach, reliability was evaluated by considering the variability in laboratory test results, layer thicknesses, stiffnesses, and measured in situ performance. The effects of input design parameters variability on predicted performance were determined using the calculated distributions of calibration coefficients. To assess the contribution of each input parameter’s precision to the precision of calculated calibration coefficients, various cases were created by including and excluding the variability in these parameters in the calibration process. These distributions were also used for rutting performance prediction and reliability evaluation of highway sections. In this way, rut depths for different reliability levels can be predicted without performing computationally intensive calculations within the design software. The results indicated that distributions of calibration coefficients calculated by using measured rut depths (performance variability) are very similar to calibration coefficient distributions calculated by using thickness and stiffness (construction) distributions. This result suggests that variability in performance can be effectively predicted by using the variability in thickness and stiffness for HVS test sections because thickness and stiffness were found to be the major factors that control the variability in measured rut depths. The effect of laboratory test results variability on calibration coefficient distributions was found to be negligible when compared to the effects of stiffness and thickness variability. Although the reliability approach proposed in this study was developed using the results of a specific laboratory test and rutting models used for design in California, the general procedure can be applied to any pavement design software for any type of distress.

Although pervious concrete material properties, mix design, and storm water applications are well documented in the literature, the structural behavior of pervious concrete pavement systems has not been investigated. A parking lot was constructed in which traditional impervious concrete was used on half of the parking lot and pervious concrete was used on the other half. The traditional concrete layer was placed on natural subgrade. The pervious concrete portion was divided into two sections with two pervious concrete mixtures and aggregate base thicknesses of 300 and 450 mm. To better understand the behavior of traditional and pervious concrete pavement systems of the parking lot, the subgrade soil properties were characterized by using plate load testing and nuclear density gauge. Furthermore, the aggregate base layers used in the pervious concrete systems were characterized by using plate load testing. After constructing the parking lot, falling weight deflectometer (FWD) testing was performed on the traditional concrete and the two pervious concrete pavement systems. In addition to summarizing the subgrade and base material properties, this paper compares the response of the three pavement systems during FWD tests. Furthermore, artificial neural network-based backcalculation models were used to better understand the response of the three pavement systems. FWD results show that a pervious concrete pavement system with 450-mm aggregate base experiences smaller measured deflections and better uniform support than the traditional concrete pavement system.

Roadside cross-drainage culverts have been found to affect vehicle accident injury levels. As a result, highway designers have commonly used three safety treatments to protect errant motorists from striking culvert openings. These safety treatments have included: culvert extension, guardrail installation, and the application of safety grating. However, the identification of the most appropriate safety treatment for roadside culverts may be challenging; accident costs may dramatically change under different road and traffic characteristics. The purpose of this study was to estimate accident costs for a wide range of road and traffic scenarios and then define the safest treatment (i.e., treatment with lowest accident cost) for a variety of traffic, roadway, and roadside characteristics. Over 3,000 highway scenarios were modeled using the Roadside Safety Analysis Program (RSAP). This study showed that the selection of culvert safety treatments should be flexible when considering different road and traffic characteristics. The findings demonstrated that culvert extension and grating were found to produce the lowest accident costs for all highway scenarios that were modeled, and guardrail protection was not recommended for any of the scenarios. Therefore, it is believed that the expanded adoption of culvert extension and culvert grates can improve overall highway safety.

One way of mitigating the negative effects of noise from road traffic is to include the external cost of noise in a road charging system. This study shows how standardized calculation methods for road traffic noise can be used together with monetary estimates of the social cost of noise exposure to calculate charges based on the social marginal cost. Using Swedish data on traffic volume and individuals exposed to road noise, together with official Swedish monetary values for noise exposure, we estimate road-noise charges for cars and heavy vehicles.

Measurement interval is crucial in obtaining stable traffic flow parameters, such as traffic flow rate, density, and speed. Credible relationships among these parameters and reasonable capacity for analysis are also dependent on the appropriate measurement interval. Nevertheless, the measurement interval has not been mentioned explicitly in most previous studies related to pedestrian traffic flow. Different researchers adopted various time intervals for traffic flow parameters measurement, and the reasons for the choice of a certain measurement interval were usually not clearly stated. This paper deals with the impact of different intervals on the results of pedestrian traffic flow parameters counting and the methods to determine the appropriate measurement interval. It takes pedestrian traffic in Shanghai Metro stations into an observation context. By video recording, pedestrian traffic parameters, including volume and density, are extracted manually through recording tapes using an initial 5-s interval for level passageway, ascending stairway, descending stairway, and two-way stairway. Taking 5 s as the basic incremental unit, traffic parameters for 10-s interval, 15-s interval, and other analogical time interval values are acquired in sequence. On the basis of the principles of measurement interval selection, the appropriate measurement interval is determined by comparing its influence on stability of hourly flow rate and invariability of pedestrian traffic status when applying different time interval values. It is revealed that a 30-s interval value is optimal for all the observed facilities in this research context. From the analysis of optimal measurement interval, it could also be inferred that traffic stability of level passageway is higher than that of stairways, and a one-way stairway is more stable than a two-way stairway. The collected data, proposed methods, and revealed pedestrian flow characteristics could be helpful in improving the theories on pedestrian traffic flow, and serve as valuable references for similar pedestrian context studies.

This paper presents a comprehensive model for ranking candidate location plans of multiple urban transit hubs, which can effectively capture various aspects of concerns in the transit hub location planning process, including the overall efficiency of the transit network, the transfer intensity, the proximity to major passenger generators/attractors, the effectiveness of hub service coverage, the compatibility with land use restrictions, and the adaptability to future developable transit concepts. Grounded on an analytical hierarchy process (AHP)-based framework integrated with fuzzy logic, the proposed model offers the strengths to effectively determine the weights for multiple evaluation criteria and to synthesize the final score of each candidate plan for comparison. Results from a case study in Suzhou Industrial Park, China, reveal that the proposed model offers some promising properties for transportation planners to use in planning of transit hub locations. Comparative studies with respect to different evaluation criteria have further demonstrated the effectiveness of the proposed model in capturing the impacts of different criteria on the decision-making process.

Bunching at bus stops can be a major problem for traffic and passengers if bus arrivals are not well distributed. Arrivals can be better staggered if bus stops are divided into more than one berth. This article presents a methodology using a bilevel optimization model for assigning public transport routes to bus stops that have been divided to increase their capacity. The upper level minimizes the user costs, and the lower level applies a public transport assignment model under congestion conditions. The model is first applied to an example network to compare different assignment configurations; it is then applied to a real case in the city of Santander, Spain. The quantified benefits of an optimal route-stop assignment show increases of 10% in average bus speed and reductions of 5% in user costs.

The location of motorway interchanges strongly affects the traffic motorways can capture and therefore the revenues for the concessionaires. This paper presents a set of optimization models aimed at assisting toll-motorway concessionaires when they set up the location of interchanges for a new motorway. The decisions are assumed to be made with the objective of maximizing profit. Road users select their itineraries according to the attractiveness of the routes, which is measured by travel costs (vehicle operating costs, accident costs, user time costs, and tolling costs). The choice is between the existing road network and a combination of existing road segments with new motorway segments. A deterministic model and two stochastic models are proposed. The latter models take into account the risks involved in motorway investment decisions. The usefulness of the models is illustrated for a real case study.

The criteria currently employed for the design of railway infrastructure on ballasted track are based on the elements of the superstructure, traffic, and bearing capacity of the subgrade. In high-speed railway, the elements of the superstructure are relatively well defined because they are based on existing experience. The category of traffic is a variable that has an influence from the point of view of the number of axles, weight per axle, and speed; i.e., it is determined a priori, depending on the operating characteristics of the line in question. The third and last point refers to the quality of the subgrade that is based on the values of the California bearing ratio test. The quality of the subgrade has a considerable influence on the behavior of the track that manifests itself in the value the deformation and settlement takes, which is caused to the rail on the passage of traffic. This is attributable to the relationship between the vertical track stiffness and the quality of the subgrade. In turn, this deformation determines the value of the dynamic overloads that are transmitted to the track and consequently its deterioration. Therefore, it would be convenient to introduce a new indicator that is related to the quality of the subgrade: the vertical track stiffness value. This paper deals with the variation in the value of the vertical track stiffness parameter as a function of different types of substructure, presenting graphs and formulations that can be used in the infrastructure design of the rail track. Mathematical expressions to obtain the vertical track stiffness as a function of the height of embankment and the modulus of elasticity of the embankment and the natural ground are obtained from the graphs and a methodology for designing the type of ground used in each layer of the infrastructure is proposed. This methodology is applied to several examples to point out that the application of these tools are of special importance in the case of high-speed lines, where it is necessary to adjust the value of the vertical track stiffness owing to the large effect it has on the value of dynamic overloads generated by unsprung masses.

In this study, a weaving section flow at a conventional roundabout traffic flow situation is being modeled using Parallel Microscopic Simulation software. The findings discuss the traffic performance of the weaving section of the roundabout in terms of level of service (LOS) under Malaysian roundabout geometric design and weaving section flow parameters. The calibration and validation process of the model was successfully made on the basis of fieldwork before the sensitivity analysis of changing parameters of flow and geometric design began. The results of the simulations indicate that slight changes made to roundabout geometric design and weaving section flow parameters can affect the performance (LOS) of the roundabout. It is possible that roundabout geometric design for Malaysian conditions, from JKR Arahan Teknik, had not taken into account the weaving section flow of the roundabout. The study suggested that a study of traffic flow in Malaysian roundabouts was needed in order to close this knowledge gap and to enable the development of models to support the design and traffic operation processes at entry, exit, and weaving sections of conventional roundabouts. However, the significant output from this research shows that by introducing a slight engineering design improvement, better traffic performance at the weaving section of conventional roundabouts can be accomplished.