It is common practice to resist hydraulic thrusts in buried piping by the use of restrained joints. The most common design method currently in use for restraint design was proposed by Roger Carlsen and is currently incorporated in the 1996 American Water Works Association Manual of Water Supply Practices-M41. The writer reviewed the assumed soil distribution, which is essential to the validity of the Carlsen method, and found it to be incorrect. However, it was also found that the resistive forces that are incorporated in the method are ultraconservative. As a result, these hidden factors of safety compensate somewhat for the use of the improper pressure distribution.

This paper focuses on the response of circumferentially cracked cast iron (CI) pipeline with the cast-in-place pipe (CIPP) lining system by evaluating stresses, relative displacements, and rotations generated by repetitive loadings, including the thermal expansion and contraction effects, actual traffic loading, backfill effects, and adjacent excavations. Detailed analytical models were developed to relate axial and vertical displacements and rotational distortions imposed on pipeline at the circumferential crack. The analytical results were used to establish laboratory test procedures to simulate repetitive loadings. Laboratory tests were performed on CIPP lined CI pipes in accordance with the analytical model. By concentrating on cracked sections of CI pipe, the mechanical aging tests provide quantitative means of characterizing the liner performance under the most severe conditions that would be anticipated during general operations.

Transportation Analysis and Simulation System (TRANSIMS) is a microsimulation model, which uses census data to generate a synthetic population and assigns activities using activity survey data to each person of every household of the synthetic population. The synthetic households generated from the census data are matched with the survey households based on their demographic characteristics. The activities of the survey household individuals are then assigned to the individuals of the matched synthetic households. A classification and regression tree algorithm program is used to build the matching tree for the activity survey households based on some demographic independent variables. The current TRANSIMS model utilizes times spent at activities as dependent variables for building the classification tree. This research instead uses the travel times for travel between activities as dependent variables, i.e., using the travel time pattern instead of activity time pattern to match the persons in the survey households with the synthetic households. This approach assumes that if the travel time patterns are the same then we can match the survey households to the synthetic population, i.e., people with similar demographic characteristics tend to have similar travel time patterns. The algorithm of the activity generator module along with the original set of dependent variables were first used to generate a base case scenario. Further tests were carried out using an alternative set of dependent variables in the algorithm. A sensitivity analysis was also carried out to test the affect of different sets of dependent and independent variables in generating activities using the algorithm of the activity generator. The paper documents the results from all these tests and provides conclusions and recommendations.

This paper explores the impact of the reduced vertical separation minimum (RVSM) implementation on the airside of a large-airport system infrastructure. The hypothesis is that the frequencies of aircraft operations at the airport threshold, both for the departures and arrivals, will increase since almost double the number of aircraft can be operated in the same quantity of airspace when all flight levels in the RVSM environment are fully utilized. Simulation models are used to test these hypotheses. Airport systems with dependent parallel runways, intersecting runways, and independent parallel runway configurations are selected for our study. The analyses use the full-day traffic of the peak months at each airport as flight inputs and are conducted for both good and poor weather conditions. Not surprisingly, the results confirm that the RVSM implementation would aggravate delay on the airside of an airport system infrastructure, especially on the airfield where the capacity is limited and during the peak hours. The simulations provide insight into where improvements might be made. The methodology developed in this work to explore the factors that contribute to delay with the RVSM implementation is generally applicable to other airport systems.

Many state agencies are shifting towards nighttime construction/maintenance especially on urban highways. While nighttime construction/maintenance has many advantages, it also has disadvantages compared to daytime construction. One major disadvantage is that nighttime construction operations may be more hazardous to both drivers and construction personnel because of visibility problems at night. Visibility depends on providing more luminance contrast to the driver than otherwise available. A system called LUMINA was developed to measure the luminance of six commonly used safety vests in nighttime construction/maintenance work areas. LUMINA was used (1) to perform field experiments that involved recording on videotape the performance of the safety vests; and (2) to convert the video movies into snapshots, to calculate the average luminance of the vests tested, and to index them. These tests were conducted not in a laboratory setting but on actual construction/maintenance sites that involved different lighting, traffic, and weather conditions. Two of the six safety vests outperformed the others significantly.

Guardrail posts made of recycled plastics are becoming candidates for use in roadside safety features due to the nature of exhibiting properties that are useful in absorbing energy. Relatively few studies have specifically addressed the performance of recycled guardrail posts in strong-post guardrail systems. Few have reported success in this area. In this study, a detailed computer simulation study is performed to evaluate the crashworthiness of the recycled content guardrail posts. Results of a full-scale crash test are also used to verify the accuracy of the finite element models used in the simulation study. Based on the investigation, it is demonstrated that computer simulations can effectively model the dynamic response behavior of a crash event and provide valuable information about the impact performance of recycled content guardrail posts. Crash simulation results indicate that when proper quality recycled posts are used the guardrail system has the potential for meeting the National Cooperative Highway Research Program Report 350 recommendations.

Despite the high percentage of large truck trips on Interstate roadways, only 24% of fatal truck crashes occurred on these roadways. About 59% of large truck fatal crashes occurred on undivided highways that do not have controlled access and have signalized intersections. These statistics suggest that truck safety research should not only be aimed at Interstate driving conditions, but should also focus on improving truck safety for secondary roadways. One approach that can be used to better understand factors that impact truck safety on arterial roadways is through the use of accident prediction models. This paper describes the use of Poisson regression and negative binomial accident prediction models for truck accidents on an urban arterial with heavy truck volumes and a large number of signalized intersections. A model combining both signal and roadway segments showed good fit and demonstrates the ability to capture the impacts of both signal and roadway segments in one model.

The paper utilizes a linearly increasing variable power vehicle dynamics model to develop the TRUCKSIM software for the modeling of truck acceleration behavior along grade sections. The TRUCKSIM software is demonstrated to produce truck performance curves that are consistent with the Highway Capacity Manual (HCM) procedures for a $120\mathrm{kg}/\mathrm{kW}(200\mathrm{lb}/\mathrm{hp})$ truck equipped with radial tires traveling on a fair asphalt surface (Pavement Serviceability Index between 1.5 and 3.0). Using the software, the sensitivity of truck performance curves to roadway and truck characteristics are quantified. Subsequently, truck performance curves that are reflective of in-field truck characteristics are developed. These truck performance curves are intended to enhance the HCM procedures in locating truck climbing lanes.

The soil stiffness gauge is a new tool for measuring the stiffness of a soil layer quickly in the field. It is anticipated that this type of portable device will be utilized in a variety of geotechnical projects in the future, since stiffness is a better indicator of the quality of soil fill than dry density. This paper examines the usefulness of the soil stiffness gauge in thermoplastic pipe installation work. Comprehensive data obtained during the initial stage of the thermoplastic pipe deep burial project in Ohio are reviewed to discuss the ability of the soil stiffness gauge to realistically measure the stiffness of the backfill soil placed around thermoplastic pipe and the ability of the soil modulus derived from the soil stiffness gauge readings to predict the horizontal deflections of the thermoplastic pipe under moderate to deep soil cover.

This paper addresses two drivers’ route choice paradigms by modeling the factors that affect drivers’ compliance with a long-term pretrip advised route and modeling drivers’ usage of en-route short-term traffic information. A travel simulator with a real network and real historical congestion levels was used as a data collection tool. A generalized estimating equations (GEEs) model with repeated observations and a binomial probit link function was used to ensure the validity of the statistical analysis. Four different correlation structures were used and compared. The results showed that familiarity with the device that provides the information and severe weather conditions increases the likelihood of complying with the pretrip advised route and following the en-route short-term information. Network familiarity and the number of traffic signals on the pretrip advised route have a negative effect on drivers’ compliance. Providing qualitative information and proximity to the destination increase the usage of en-route traffic information.

A modified approach to treat traffic flow parameters (flow, density, and speed) has been introduced in this paper. A queuing analysis has been conducted on traffic flow data on Interstate 94 in the Minneapolis–St. Paul metro area. A methodology has been developed to calibrate loop detector count data. Corrected flow data has been subjected to analysis using queuing analysis to compute densities and speeds on freeway sections. Statistical analysis identifies “active bottleneck” locations on freeways and sections where bottlenecks occur because of disturbances caused by downstream bottlenecks propagating backwards in the form of shockwaves. A sample of 6 days on Interstate 94 was considered for the analysis. Our analysis reveals that the same section cannot always be characterized as a “bottleneck” location; at some times it is active and at others it is subject to downstream bottlenecks. Traffic flow characteristics change and that leads to changing situations on each freeway section.

The study consists of a systematic simulation evaluation of transit signal priority (TSP) impacts on the operations of a single signalized intersection within a coordinated arterial system. The study demonstrates first that in general TSP provides benefits to transit vehicles that receive priority. Second, TSP has a marginal systemwide impact for low traffic demand, although as the demand increases, so do the systemwide disbenefits of TSP. Third, the systemwide impact of TSP is directly proportional to the frequency of transit vehicles. Fourth, TSP impacts are sensitive to the demand distribution at a signalized intersection. Specifically, transit vehicle arrivals on heavily congested approaches may result in systemwide benefits if the conflicting approaches are not congested. Alternatively, transit vehicle arrivals on lightly congested approaches may produce significant systemwide disbenefits if the conflicting approaches are heavily congested. Fifth, the systemwide benefits of TSP are dependent on the phase at which the transit vehicles arrive, especially if the cycle length is maintained within the priority logic. Sixth, the systemwide benefits of TSP are highly dependent on the optimality of the base signal timings. Finally, transit vehicle dwell times at nearside bus stops can have significant systemwide impacts on the potential benefits of TSP.

This paper proposes a logit-based stochastic user equilibrium (SUE) problem for networks with entry-exit toll schemes that result in nonadditive path costs. First, it develops a strictly convex minimization model in terms of path flows for the problem. Second, by decomposing the original problem into two kinds of subproblems that possess the additive path costs, this study designs a novel two-stage stochastic loading algorithm exempted from path enumeration or generation. Hence, the method of successive average embedded with the proposed stochastic loading algorithm can identify the logit-based SUE link and entry-exit flows. Finally, two numerical examples are used to demonstrate the proposed model and algorithm.

The percentage of sport-utility vehicles, light-duty trucks, and passenger vans in the on-road light-duty fleet is steadily increasing. The implications for modeling emissions from on-road vehicles are significant since light-duty trucks produce, on average, more emissions than passenger cars. Although not frequently considered in calculating emission rates, differences in the average speeds of passenger cars, light-duty trucks, sport-utility vehicles, and passenger vans may influence emissions. This paper investigated whether the different classes of passenger vehicles operated differently on-road. Spot speed studies were used to determine differences in operating characteristics for three subgroups of the passenger car fleet. Results are presented for studies on freeways and arterials.