The focus of this paper is the use of information from automatic vehicle identification (AVI) systems to help estimate short-term trip origin–destination (OD) matrices in an urban environment. In this paper, a method is proposed for using sample link choice proportions and sample OD matrix information derived from AVI data sampled from a portion of vehicles to estimate population OD matrices with the AVI data collection points acting as the origins and the destinations. This method is extended to estimate ramp-to-ramp freeway OD volumes. The value of such information is demonstrated using a large urban freeway network equipped with an AVI system. Based on a comparison of the OD estimate accuracies, with and without the AVI data, it was found that using AVI data in OD estimation improves significantly the accuracy of the OD matrix estimates.

Traffic comprises a primary input to any pavement design methodology. As pavement design evolves from traditional empirically based methods toward mechanistic-empirical (M-E), there will be a greater emphasis placed on accurate characterization of the distributions of axle loads, because they are entered directly into pavement response models. Known as load spectra, these distributions of axle weight are often complex and not well represented by individual theoretical statistical distributions. This research proposes a mixed distribution model of two or more theoretical distributions to accurately characterize axle load spectra. This paper details the model development and demonstrates its predictive capability using weigh-in-motion data from 13 sites in Alabama. The data show the predictive capability of the mixed distribution model through high $R^2$ values, exceeding 0.96 in all cases. The typical axle load distribution in Alabama is comprised of a combination of lognormal and normal distributions.

This paper presents a simulation-based quasidynamic network assignment (DNA) procedure that facilitates the representation of changes in route choice behavior of users traveling on extended urban networks. The procedure is based on the building of regularly updated transient demand matrices. Its potential to facilitate on-line traffic monitoring of the effects of implementing real-time guidance systems is investigated both theoretically and empirically through testing in real urban network conditions. The DNA model performance is assessed with respect to the assumed origin–destination $(O–D)$ matrix split sequence, the temporal length of updating periods, in which the total assignment period is divided, and the total size of $O–D$ demand. The simulation results indicate the beneficial impact of dynamic optimal path information provision using the DNA model on network performance. The benefits of information updating frequency, ranging from $30\text{to}5\min$ , are found to increase with respect to the growing levels of network congestion.

This study investigates the performance of several existing automatic incident detection algorithms along the Central Expressway in Singapore and freeways in Melbourne, Australia. These algorithms were originally developed for freeways in the United States. Thus, it is of interest to evaluate how they would perform when applied to cities in other countries. The evaluation is carried out on two databases containing 160 and 100 incidents collected from Singapore and Melbourne, respectively. These databases reflect differences in vehicle detector system used to collect traffic parameters and in driver behavior. The following empirical findings were obtained: (1) the Minnesota and Standard Normal Deviate (SND) algorithms appear to possess transferable properties as well as being able to receive wide-area traffic measurements from a machine-vision vehicle detector system; (2) California Algorithm number 7 and the Double Exponential Smoothing algorithm performed poorly in Singapore but may be transferable to Melbourne freeways; and (3) no significant difference in average efficiencies between the better-performing algorithms (SND and Minnesota) on both databases.

This project was a pilot study to examine side friction values for the geometric design of low-speed urban horizontal curves. The friction factors calculated from measured curve radius, pavement cross slope, and vehicle speed within the curve were compared with those in the 2001 A policy on geometric design of highways and streets. The findings from the five study sites suggest that the current low-speed urban side friction values may be overly conservative, in that a sizeable proportion of drivers can exceed the intended design speed. The average friction factors calculated for different categories of passenger cars differed among the categories. A significant amount of geometric irregularities, perhaps due to either construction or maintenance practices, were found among the curves examined. The paper also contains practical advice for those engaged in future field data collection.

Road roughness indices such as the International Roughness Index, Quarter-car Index, and root-mean-square vertical acceleration are useful as indicators of the level of pavement serviceability performance. Each of these summary roughness statistics offers a convenient index for monitoring the trend of pavement roughness deterioration with time. However, they do not retain the actual contents of pavement surface roughness. Such detailed roughness information may be useful for maintenance operations, detection of pavement surface distresses, and detailed analysis of the trend of pavement roughness deterioration. This paper presents an application procedure based on wavelet theory to offer supplementary information to a roughness index and provide additional information on the characteristics of the roughness profile of interest. The procedure is able to identify the characteristics of a pavement roughness profile in both the frequency and distance domains. This study proposes methods of roughness data processing using different wavelet transformation and analysis techniques to extract useful information for pavement maintenance management. Numerical examples based on measured roughness profiles of the Long Term Pavement Performance (LTPP) database are presented to illustrate the types of useful information derivable with the proposed method of analysis. It is demonstrated that using appropriately selected analysis methods and wavelet parameters, detailed roughness features of interest to pavement engineers not currently available from summary roughness statistics can be obtained together with summary roughness statistics as part of the roughness survey report for highway agencies.

For years researchers and practitioners alike in the pavements and materials industry have been performing forensic analyses to determine the origin of hot-mix asphalt pavement permanent deformation (rutting) failures. The investigations typically involve traffic control, coring, excavation, and significant materials testing. These investigations are costly and very inconvenient for road users. Although expensive and inconvenient the investigations are necessary in order to plan appropriate rehabilitation activities. Under the National Cooperative Highway Research Program Project 1-34A, a method has been developed to determine the relative contributions of structural layers to total rutting in flexible pavements from a simple analysis of a pavement’s transverse surface profile. A recommended test method in standard format was developed that provides the industry with an extremely valuable analytical tool that could eliminate the need for expensive and inconvenient forensic analyses in many cases.

A concrete slab was constructed at Texas A&M University to investigate environmental effects in terms of temperature and moisture effects on the behavior of jointed plain concrete pavements. The slab behavior was delineated relative to equivalent linear temperature and humidity differences as a function of time. As expected, the trends of these differences were found to relate with the trends of ambient temperature and relative humidity. The slab had daily periods of tensile and compressive strain corresponding to the daily changes in the ambient temperature and relative humidity. Furthermore, the trends in the slab displacements were clearly dependent upon the changes in ambient temperature and slab temperature gradients. Drying shrinkage and creep strains primarily in the vicinity of the top surface appeared to cause an overall shift in the slab movements. This shift manifest in both the strain and vertical displacement of the slab was determined from data collected up to $2\text{years}$ after placement of the concrete.

Performance of flexible pavement has long been recognized as an important parameter in the design of flexible pavements. Pavement surface condition evaluated using visual inspection is periodically done to assess pavement performance over time. A distinct performance curve is then constructed for each pavement structure that relates the pavement surface condition to service time or accumulated $80\mathrm{kN}$ equivalent single axle load applications. The presented flexible pavement overlay design models are constructed using performance curve parameters to provide an adequate overlay thickness at any given future time. The undertaken approach attempts to compensate an existing pavement structure for the loss in performance (strength) that it has endured over a specified service time. In essence, this approach is similar to the mechanistic methods of overlay design that make a compensation for the loss in a particular strength indicator such as the commonly used deflection method. Therefore, compensation is made for the loss in performance as represented by appropriately selected performance curve parameters. Performance parameters are then converted into equivalent relative strength indicators, which are in turn converted into equivalent overlay thicknesses. The relative strength indicators deployed in this paper are the structural number and gravel equivalent used by the American Association of State Highway and Transportation Officials and the California Department of Transportation design methods of flexible pavement, respectively.

The effect of installation procedures on the field performance of existing high density polyethylene (HDPE) pipe used for drainage applications on highway projects was investigated. A total of 45 HDPE pipes were inspected at sites in South Carolina that were statistically selected based on geographical location, pipe diameter, use, and age. The condition of each pipe was not known prior to selection for inspection. Both the external and internal conditions of the pipe were evaluated with respect to AASHTO and ASTM specifications, measurements of pipe deflection with a mandrel set to 5% deflection, and visual inspections of the pipe interior using a video camera. The video camera inspections revealed circumferential cracks in 18% of the pipes, localized bulges in 20% of the pipes, and tears or punctures in 7% of the pipes. Deflections greater than 5% were observed in 20% of the pipes. Installation problems such as poor preparation of bedding soils, inappropriate backfill material, and inadequate backfill cover contributed to the excessive deflection and observed internal cracking in pipes with observed damage. Appropriate construction procedures are essential in achieving a proper installation.