With the rapidly increasing requirements of bridge maintenance and the limited budget available for this maintenance, the cost optimization of long-term maintenance strategy considering the network-level bridge system under an allowable deterioration level is becoming an important problem. However, the total maintenance cost is a function of the number of bridges and their deterioration degrees, the planning period, and the maintenance methods. The selection of the optimization algorithm is important to get the optimal solution of this problem. In this research, using the bridge deck as an example, the search procedure and optimization technique of the long-term maintenance cost of a network-level bridge system are presented using a genetic algorithm. A population of maintenance strategies evolves from one generation to the next generation by applying the principles of natural selection and survival of the fittest. The feasibility of this method is demonstrated using a real-world example, and the results are compared with the conventional maintenance planning. In addition, several maintenance policies are suggested and compared.

Many water hammer studies concentrate on the main pipeline and pump stopping. Important details can be overlooked. The rigidity of pipe walls, coatings, and surrounding fill on water hammer in pipes is evaluated. It is shown that backfill increases rigidity and celerity marginally, but pipe material is a major factor in water hammer pressures. The effect of air is to reduce wave celerity but increased surging can occur with some pipework configurations, particularly if air can be trapped. Pump startup can then result in severe water hammer. The correct selection of air valve size and standpipe used to minimize water hammer is discussed. The problem of air valves slamming shut during discharge is investigated and can be remedied with a nomograph. It is shown that large volume standpipes can reduce water hammer due to air valve slamming by providing an air cushion. Other problems of air release and sizing and positioning of air valves are discussed in order to reduce the problem of water hammer.

In traditional black-spot programs aimed at improving highway safety, locations are identified as accident prone based on the total number of accidents. This criteria provides no consideration of whether the accidents were caused or could be corrected by road improvements. This traditional method results in the identification of locations that are not truly hazardous from a road-safety authority perspective and consequently may lead to a misapplication of safety improvement funding. Therefore, accidents should be categorized into one or a combination of the three highway system components: the driver, the vehicle, and the road. In previous work, a procedure has been described that allows each accident to have a membership in each of the three highway system components. This paper describes the application of this procedure for the identification of accident-prone locations. The membership of each accident in the road environment component is used to represent the correctability of accidents by road improvements. Each accident is then weighted by its correctability. The effect of weighting accidents by their correctability is discussed, and the usefulness of the approach is demonstrated.

The development of a codable model for the design of lane-use and signal-phase control at isolated intersections is valuable especially in developing countries where experienced traffic engineers are scarce. Extensive research concerning the design of signal phases and timing have been conducted in the past while very little has been done for the optimal design of the lane-use or lane-configuration of intersection approaches. However, poor matching of lane-use design and signal-phase design also produces a poor overall result. It is therefore necessary to integrate the design of lane uses and signal phases, and perform the optimization simultaneously. A mixed integer linear programming model is introduced for this purpose. The resultant designs are verified by comparing their performance indices with that of the existing designs as computed by TRANSYT-7F. The traffic data used are collected from a selected area of Shenzhen, one of the largest special economic zones of the People's Republic of China. The results indicate significant improvement in minimizing overall delay, stop, and fuel consumption.

The assessment is based on the analyses of pavement blowups presented by the writer and his coworkers Dallis and Shade. The introduction reviews briefly the various early attempts to clarify the blowup phenomenon. The next section describes the blowup mechanism, the adopted criterion of the “safe temperature increase,” and an outline of the analytical methodology this presentation is based on. The third section contains the analytical solutions for three typical pavement problems, the description of steps for their numerical evaluation as well as a list of the used pavement parameters, and a graphical presentation of the obtained results. The fourth and fifth sections contain a discussion of the practical implications of the presented results for concrete pavement design, as well as for assessing pavement blowups after years of service. Also presented are a number of specific pavement problems and suggestions of full-scale tests for the determination of the identified pavement parameters.

This paper provides a framework for the development of Weibull reliability factors (since they describe “length of life” or endurance over time) for joint faulting models using field data from the Strategic Highway Research Program's Long Term Pavement Performance (LTPP) database. There is a need to address pavement design in a manner that will incorporate such factors as climatic conditions, soil conditions, and load transfer conditions on a comparative basis. In order to maximize the utility of the calibration process it is important for the pavement designer to understand the underlying mechanism(s) relative to a particular distress manifestation. It is in this light that field joint faulting data were analyzed and calibration factors developed on the basis of distress mechanism(s).

Many data-collection methods are available from simple manual methods to advanced automatic image processing techniques. For many practical purposes video recording has become a widely used tool. Though this method is simple and is extensively used, accuracy in estimating actual speed and associated measurement errors have not been quantitatively examined. This paper investigates the mathematical properties of measurement error in vehicular speed data reduced from video images. Primary focus was on the measurement-error probability function, which incorporates the effects of the embedded video camera time-base resolution, fiducial mark interval, and actual vehicle speed. Mathematical derivations of the probability density function (PDF) are presented, and a Monte Carlo simulation technique was applied verifying the mathematically derived probability function. Both graphical comparisons and goodness-of-fit tests demonstrated very good agreement. The probability function presented in this paper provides a very useful tool because it allows traffic engineers to quantify in advance the probability of occurrence of certain measurement-error magnitudes and to adjust the data-collection plan accordingly.

Temperature effects on rigid pavements have been shown to be significant fatigue contributors in combination with stresses produced by load, particularly at slab corners. A construction method for rigid pavement utilizing waste plastic forms to create dome-shaped cells in an orthogonal array was analyzed for stresses resulting from the application of a standard highway equivalent single axle load (ESAL). In this paper, cellular rigid pavement (CRP) is analyzed to compare temperature effects using the finite-element method. Bottom temperature tensile stresses are significantly lower for CRP than for the comparable solid slab, and in combination with load tensile stresses, vary from slightly higher to very much lower. Top tensile stresses due to temperature exceed the slab strength in the solid slab while top stresses are not significant in the CRP slab. The application of CRP appears to mitigate to a considerable extent the fatigue effect of temperature stresses in pavement of equal thickness to that of solid slabs and may, in combination with load stress, result in pavement with equal or greater fatigue life.

This paper reviews a class of models that combine equilibrium traffic assignment and intersection control into a single analysis framework under the assumption of flow-responsive signal settings. The most significant feature of these models is their capacity to take into account explicitly the mutual interactions between signal control policies and user route choices; such interactions are usually disregarded both in ordinary traffic assignment models and in traditional traffic engineering practice. After defining the combined traffic assignment and control problem, and reviewing alternative formulations and solution algorithms, this paper discusses possible approaches to modeling the various types of link interactions that arise from the joint use of intersections by competing traffic movements. Important conceptual issues and implementation aspects are considered, and their potential policy implications are emphasized. The main conclusion of the survey is that, while the theoretical properties of combined traffic assignment and control models have been studied over the last two decades and are now well understood, there seems to be a significant lack of empirical results and real-world applications, that are needed in order to promote the transfer of this modeling approach from research to professional practice.

Due to the combined influence of traffic loading and environment, the structural condition of pavement deteriorates with time. Studies on structural damage, which usually results in functional deterioration, is important for the highway engineer to plan the maintenance/strengthening strategies to extend the life of pavements. In the present investigation, the data collected under the R-6 research project of the Ministry of Surface Transport, India, has been used to develop prediction models and growth curves for rebound deflection, rut depth, and crack area of pavements considering two types of surfacing: BM (bituminous macadam) + PC (premix carpet) and BM + AC (asphaltic concrete), commonly practiced in India. The performance of the pavements were studied and comparative analysis was made in terms of growth in deflection, rut depth, and crack area. An attempt has been made to develop failure envelopes based on selected critical rut depth criteria. The results are useful to decide the timing for maintenance/rehabilitation programs.