This paper presents the methodology developed for the use of continuous vertical track deflection measurements from a moving loaded rail car to map the subgrade condition along a railway line. This analysis of deflection data was developed following the collection of more than 12,000 km of measurements. It was evident from the collected data that unprocessed deflection measurements are heavily effected by the track surface condition such as joints and geometry irregularities so as to obscure the deflections because of poor subgrade support. A filtering method was employed to minimize the influence of the surface condition which occur at short wavelengths and show the variations in track deflections because of changes in subgrade conditions which occur at longer wavelengths. The resulting processed data are compared with the geology over two study railway subdivisions to demonstrate that the processed vertical track deflection measurements are representative of the subgrade conditions. The filtering process, examples of the effect of track surface on the deflection measurements, and the limitations of the resulting data are also discussed.

The finite-element method was used to quantify the effect of temperature and speed on contact area, deflection, and three-dimensional contact stresses of a free-rolling wide-base tire. The tire model comprised material properties identified in the laboratory and/or provided by the tire manufacturer (hyperviscoelastic rubber and linear elastic reinforcement) and accurate geometry. The model was validated using measured deflection and contact area. The analysis matrix consisted of 81 cases resulting from a combination of three loads, tire-inflation pressures, speeds, and temperatures. Four criteria were used to compare contact stresses: range, average, root-mean-square error, and coefficient of determination. Speed and temperature influence the contact area more than deflection. Longitudinal contact stresses were the most affected, followed by transverse contact stresses. In general, under constant load and tire-inflation pressure, the influence of temperature was more significant on the considered output variables than the effect of speed.

Adaptive traffic-signal control (ATSC) is a traffic management strategy in which traffic-signal timings change, or adapt, based on observed traffic demand. Although ATSC can improve mobility, it also has the potential to reduce crashes because mainline stops should be reduced. This paper aims to evaluate the safety effectiveness of ATSC using the empirical Bayes method. This analysis examines 47 urban or suburban intersections where ATSC was deployed in Virginia using 235 site-years of before data and 66 site-years of after data. Installing ATSC was found to produce a crash modification factor (CMF) for total intersection crashes of 0.83 with a standard error of 0.05. This CMF was statistically significant at a 95 percent confidence level. Fatal and injury crashes did not change by a statistically significant amount, indicating that the primary safety benefit of ATSC was reduction in property damage crashes. Analyses of ATSC safety effects by crash type, by traffic volume level, and by operational improvement magnitude were also performed. All crash types were found to be reduced, but safety benefits varied from corridor to corridor and by volume levels. It was concluded that ATSC installation can potentially reduce total crashes at highway intersections and that public agencies should consider ATSC’s safety and mobility benefits when justifying ATSC projects.

The use of roundabouts is gaining popularity in North America for their safety, capacity, and environmental benefits. Studies have shown that roundabouts can significantly reduce injury collisions compared to stop control and traffic signals. As more roundabouts are constructed, there will be an increased need for a detailed analysis of their safety performance. Traditional road-safety analysis of roundabouts has relied on the use of historical collision records. This approach offers a less-complete understanding of roundabouts safety and their effects on the behavior of drivers, pedestrians, and cyclists. This paper represents a case study where automated video-based traffic conflicts analysis is used to diagnose safety issues at a roundabout in Vancouver, British Columbia, Canada. Traffic conflicts are automatically identified and analyzed to develop an in-depth understanding of the behavior of road users and the causes of traffic conflicts. Conflicts contributing factors were identified and safety countermeasures are presented.

Despite the fact that both traffic researchers and highway agencies have devoted considerable efforts over the past few decades to improving intersection safety, the development of effective strategies remains a challenging task. This research presents an integrated dilemma zone protection system (DZPS) for contending with the safety issues caused by the presence of a dilemma zone, a primary factor contributing to the rear-end collisions or side-angle crashes at intersections, especially at those experiencing high-speed traffic flows. The entire paper includes three parts: (1) development of an integrated system for protecting vehicles within the dilemma zone; (2) procedures to calibrate those key system parameters with field data at a candidate intersection; and (3) design of a per-deployment assessment process for evaluating such a design prior to its field deployment. The proposed DZPS, developed with a target intersection’s traffic characteristic data and geometric constraints, consists of three principal modules: variable message sign (VMS) for advanced warning or speed display, wide-range sensors to track individual vehicles in the dilemma zone, and a decision module to execute the all-red extension function. Based on a proactive design notion, the proposed DZPS can first use the VMS to inform the approaching drivers of a yellow or red phase ahead and prepare to stop, or to display the speed of the discharging traffic flows from the stop line during a green phase. The information will help compliant drivers to adjust their speeds in a timely manner so as to avoid rear-end collisions. For those aggressive/noncompliant vehicles, the DZPS system’s wide-range sensors will track the evolution of their speeds and locations within the dilemma zone at the interval of every 0.1 s, and then determine whether or not an all-red extension call shall be granted to prevent such vehicles from incurring potential side-angled crashes with vehicles from the side street. Recognizing that reliable evaluation of a deployed DZPS’s effectiveness needs the field data over a sufficiently long period, this study has presented the process for conducting a predeployment assessment with well-calibrated simulation experiments. The effectiveness of the proposed system, demonstrated with the results of the case study at the intersection of highway U.S. 301 at Croom Station Road, Upper Marlboro, Maryland, has also been summarized in this paper. Overall, the proposed system, from both the proactive and reactive perspectives to protect drivers, exhibits quite promising properties for use in practice.

To avoid bias caused by the high percentage of rear-end collisions in the generic models, only the observed sideswipe collisions on Highway I-5 in the central Puget Sound, Washington State, area are used to analyze the matched case-control logistic regression model. Considering the spatial-temporal characteristics of traffic flow and short-term variation of the sideswipe collision occurrence, a comprehensive analysis of sideswipe collision occurrence and its relationship with the freeway flow across lanes and detector locations are studied. The results imply that sideswipe collisions are more likely to occur at straight and level segments of multilane freeways in off-peak hours. High average occupancy and low average flow and speed variance upstream of collision location tend to increase the probability of sideswipe collision in congested scenarios. In contrast, high average speed and coefficient of variation in speed, low speed variance and coefficient of variation in occupancy, and high average absolute difference in speed between adjacent lanes downstream of collision location may decrease the likelihood of sideswipe collisions in uncongested conditions. Furthermore, the average absolute difference in occupancy and speed between upstream and downstream of the collisions location leads to an increase in the occurrence of sideswipe collisions, while standard deviation of absolute difference in occupancies and speeds exerts opposite effects. The sideswipe collision model proposed is validated using sideswipe collision data of SR 520 freeway, and both the transferability and stability of the proposed sideswipe collision model are statistically tested.

The automated techniques used to collect pavement conditions on county roads are relatively expensive for local agencies. This study evaluates the possibility of reducing the amount of pavement condition data collected in each survey to optimize the costs of data collection. This study applies multiple imputation analyses as an assistant tool to estimate the uncollected condition data at the network level. Another objective of this study is to determine the most cost-effective pavement condition data collection frequencies. By using a case study of secondary paved highways in Wyoming, it was concluded that uncollected condition indices can be predicted using the initial/historical values. The imputation models developed in this paper provide good estimations. Cost analysis of county roads for two counties demonstrates the significant amounts of cost saving when applying the proposed imputation strategy during data collection process. Therefore, pavement condition data is not recommended to be collected for the whole network annually on county roads. A less expensive sequence can be adopted instead where the data that is not collected can be predicted.

Based on field data collected at nine roundabouts in Gold Coast, Australia, this paper evaluates the performance of the capacity estimation for single-lane roundabouts using analytical models [including the highway capacity manual (HCM) 2000 model, the German Highway Capacity Manual (GHCM) model, the signalized and unsignalized intersection design and research aid (SIDRA) model and a new roundabout capacity (NRC) model] and an empirical model (the HCM 2010 model). First, this study calibrates critical gaps, follow-up times, and conflicting flows. Compared with the capacities measured in the field, the authors carry out a study to analyze the accuracy of the HCM, GHCM, SIDRA, and NRC models. The results show that the five models underestimate capacity but the NRC model produces a smaller range of relative error ($-1.07$ to $-5.74\%$) and root-mean-square deviation (47.68) than the HCM 2010 ($-4.62$ to $-16.14\%$ and 105.00, respectively), HCM 2000 ($-5.76$ to $-17.21\%$ and 115.29, respectively), GHCM ($-8.95$ to $-21.26\%$ and 146.82, respectively), and SIDRA ($-5.15$ to $-17.51\%$ and 113.48, respectively) models. Accordingly, the NRC outperforms the other four models for the surveyed roundabouts. The five models estimate a similar capacity in low and medium traffic volumes, and exiting vehicles play an important role in high traffic volumes, and at high traffic condition exiting vehicles warrant more entry opportunities that exceeds the impact of high circulating volumes on entry capacity.

The diverging diamond interchange (DDI) is growing in popularity as an interchange treatment, yet there is rather limited guidance available on signal timing practices. One particular area of concern is the coordination of a DDI along with neighboring intersections in an arterial. This study examines three different cycle length strategies for DDI coordination: (1) using the full cycle length of the corridor; (2) using a half-cycle; and (3) using a previously described three-phase scheme intended to manage queues within the DDI. Six different origin-destination (O-D) scenarios are tested in a microsimulation study. Results are presented in terms of the number of stops, movement delays at the DDI, queue lengths, and delay by O-D path. The outcomes show that the half-cycle strategy yielded lower total and average delays yet resulted in more stops along the arterial and higher arterial O-D path delays. The full-cycle option, meanwhile, tended to achieve fewer stops and lower delays for arterial routes but increased total and average delays for other movements. The three-phase strategy often reduced delays and queue lengths for the arterial movements exiting the DDI, but increased these for other movements.

This paper has derived a preflood road maintenance strategy. It provides an innovative approach by upgrading pavement strength now (Year 1 of the analysis) with a thin overlay, and then evaluating pavement lifecycle performance if a flood comes in different years. An after-flood treatment strategy would also be a part of this strategy package. The study has considered normal deterioration after a treatment given in Year 1 and uses the new roughness and rutting based road deterioration (RD) models to predict after-flood deterioration before providing postflood treatments. The study has used highway development and management (HDM-4) model for obtaining after-flood treatments. The results show pavement performance, necessary treatments at Year 1 and any year, required budget, and economic results. For a case study in Queensland, Australia, the treatment cost in Year 1 was about $21.13 billion, and the total preflood strategy cost is $37 billion to $38 billion. A thin overlay is adequate for after-flood rehabilitation. This preflood strategy is compared with a recently derived postflood strategy, and it appears that a preflood strategy can maintain the network better and demonstrate positive economic benefits.

This study aimed to compare pavement responses caused by impulsive dynamic loading and moving vehicular loading using mechanistic pavement analysis. Finite-element (FE) models were developed to simulate falling weight deflectometer (FWD) loading with axisymmetric FE models and to simulate moving vehicular loading with three-dimensional (3D) FE models. Two flexible pavement structures with different asphalt layer thicknesses and temperature profiles were considered in the analysis. The FE models simulated dynamic impulse loading during FWD testing and moving tire loading patterns with 3D tire-pavement contact stresses. It was found that the pulse durations of compressive stresses in the asphalt layer were significantly affected by speed and pavement depth in what can be described as an exponential relationship. However, pulse duration was found to be pavement-dependent, and the quantitative relationship between pulse duration and speed and depth could only be developed for each individual pavement structure. The equivalent speed of FWD loading to moving loading varies depending on the type of response, asphalt layer thickness, and temperature. The usual assumption of FWD loading as representative of truck loading at typical highway speeds was only valid for pulse durations of compressive stresses. FWD loading caused greater pavement responses than moving tire loading at the highway speed under the same loading magnitude as the asphalt layer thickness decreased or the temperature increased. The study results emphasized the importance of using moving tire loading in mechanistic analysis of pavement responses.

Congestion has become highly recognized as a worldwide traffic problem, as traffic demand has grown steadily over the past few decades. Variable speed limits (VSLs) are an intelligent transportation system (ITS) measure that limits mainline flow to mitigate bottleneck congestion. Currently, VSLs have become proactive based on short-term prediction. Proactive VSLs succeed in simulation evaluations, but few have been deployed in the field and their real-world effectiveness has not been proven. Various factors may lead to this limitation, such as the absence of reliable field application software, accuracy of prediction models, and high computation time for proactive control. To address this research gap, this study reports a preliminary VSL test and details its implementation results on Whitemud Drive, Edmonton, Canada. First, based on field traffic measurements before VSL control, recurrent bottleneck locations are identified. Second, the proactive control algorithm is briefly introduced. Then, a software application is designed to realize all necessary functions for VSL field implementation. With all these in hand, the preliminary field test was conducted and the VSL control performance and reliability are evaluated. Finally, the results for before and after VSL control implementation are analyzed in depth. The analysis compares average traffic speed, standard deviation of speed, total travel time, and total travel distance. The results from this study confirm that proactive VSL can relieve recurrent traffic congestion effectively.

This paper documents the in-place recycling of a high-traffic project (12,000 vehicles per day) on U.S. highway 49 (US-49). Sections built included asphalt emulsion–stabilized cold in-place recycling (CIR), portland cement–stabilized CIR, cement-stabilized full-depth reclamation (FDR), and traditional construction. This paper’s objective is to present a case study of US-49 construction and performance through approximately 4.5 years of service. Performance was characterized by a distress survey, cored properties, and falling weight deflectometer testing. In particular, findings demonstrated performance and economic trade-offs between cement CIR and emulsion CIR, which could be directly applied to planning decisions. Emulsion CIR exhibited sufficient rutting capacity but reserve cracking capacity, at higher costs relative to cement CIR. Cement CIR, however, was more economical and exhibited excess rutting capacity but not excess cracking capacity. Because there is little need for reserve capacity of one distress when other distresses are past capacity, this paper proposes balanced binder blends (examples might include 2.5% emulsion with 2% cement, or 3% emulsion with 1.5% cement) for future consideration because they can provide sufficient capacity for multiple distresses while balancing economics.