Showing papers in "Journal of Transportation Engineering-asce in 1988"
TL;DR: In this article, the authors present an analytic model for the design of an optimal feeder bus network for accessing an existing rail line, which avoids the sequential approach and combines these three basic variables.
Abstract: Existing studies of transit network design deal separately with the problems of determining the optimal route spacing and operating headway, and that of determining the optimal stop spacing. This paper presents an analytic model for the design of an optimal feeder bus network for accessing an existing rail line, which avoids the sequential approach and combines these three basic variables. Our results with regard to bus‐route spacing and headway are similar to those obtained previously, indicating that route spacing and operating headway are not highly sensitive to changes in the relevant system parameters. With regard to bus‐stop spacing, three different cases are considered, reflecting three different stop‐spacing policies. In the first case, bus‐stop spacing is specified as uniform over the entire area. In the second case, stop spacing is constant along any given route. In the third case, stop spacing may vary both between and along routes. Closed‐form solutions are presented for the first two cases. T...
148 citations
TL;DR: Analysis of data collected from three routes of the Southeastern Michigan Transportation Authority is used as a case study and concludes that some type of distance‐based fares could be used without significantly increasing the dwell time.
Abstract: This paper focuses on the effect on passenger dwell time from a complicated fare structure on a bus transit system. Analysis of data collected from three routes of the Southeastern Michigan Transportation Authority (SEMTA) is used as a case study. SEMTA uses a zone fare system. The nine different fare type and payment methods are found not to affect the dwell time significantly. Regression analyses are used to determine independent equations for the boarding and alighting times as a function of the number of passengers at a stop. These equations are compared to those found by past researchers. While the alighting times are similar, the boarding times are much less affected by the number of passengers at a stop. Using Kolmogorov‐Smirnov good‐ness‐of‐fit testing, the aggregate boarding and alighting times are also tested and found not to be significantly different from a lognormal distribution. The research concludes that some type of distance‐based fares could be used without significantly increasing the d...
70 citations
TL;DR: A review of the relevant theoretical results in order to call them to the attention of civil engineers involved with pavement management systems can be found in this article, where a variety of problems involving inspection, repair, and replacement are considered.
Abstract: The problem of scheduling maintenance for pavements in an optimum fashion has been approached in a variety of ways by researchers and practitioners. However, the Markov decision process has found very limited use despite the fact that cumulative damage is readily modeled by a Markov chain and that a wealth of immediately applicable theoretical results exist in the literature. The solutions are known for a variety of problems involving inspection, repair, and replacement, making it possible to solve directly for an optimal policy in the form of a control law. This paper reviews some of the relevant theoretical results in order to call them to the attention of civil engineers involved with pavement management systems.
69 citations
TL;DR: In this paper, a mathematical programming procedure for routine maintenance activities at the network level developed for incorporation into the existing pavement maintenance management system is described, which can be used for road repair.
Abstract: This paper describes a mathematical programming procedure for routine maintenance activities at the network level developed for incorporation into the existing pavement maintenancemanagement system...
63 citations
TL;DR: In this paper, the importance of walking as a significant urban travel model in the total transportation system of an area has been recognized in the industrial nations of the West in recent decades.
Abstract: In recent decades, the importance of walking as a significant urban travel model in the total transportation system of an area has been recognized in the industrial nations of the West. In rapidly ...
61 citations
TL;DR: In this paper, the authors developed a simulation model to calculate the reliability/performance of pavements, in which all of the design variables are assumed to be probabilistic and normally distributed.
Abstract: A simulation model to calculate the reliability/performance of pavements is developed. The computer program, Reliability Analysis and Performance of Pavements (RAPP‐I), employs Monte Carlo simulation techniques to solve the design equations (e.g., AASHTO, Premium) in which all of the design variables are assumed to be probabilistic and normally distributed. RAPP‐I, in conjunction with the respective design model, calculates the present serviceability index (PSI) of pavements in one‐year increments. In addition to uncertainties attributable to the design factors, errors due to idealization of the model are included in the PSI calculation. By comparing the computed PSI with the terminal PSI, assuming that both are normally distributed, standard probabilistic techniques are employed for calculating pavement reliability. An expression for calculating the “expected” life of pavements, employing the reliabilities at various ages, is proposed. The expected life is found to be a convenient measure for comparing t...
52 citations
TL;DR: In this article, the authors evaluate the use of recycled rubber in hot mix pavement applications and conclude that the rubber-modified surfacing is cost-effective, based on an analysis of life cycle costs, but does not include potential intangible benefits of the rubber modified system, such as increased skid resistance and noise reduction.
Abstract: The Alaska Department of Transportation and Public Facilities (ADOTPF) is presently evaluating the use of recycled rubber in hot mix pavement applications. The benefits of adding rubber to the mix include increased skid resistance under icy conditions, improved flexibility and crack resistance, elimination of a solid waste, and reduced traffic noise. The major disadvantage of these rubber-modified mixes is their high cost in relation to conventional asphaltic concrete pavements. A comparison of the economics of the rubber-modified system with that of the conventional pavement shows that the rubber-modified surfacing is cost-effective. This conclusion is based on an analysis of life-cycle costs, but does not include potential intangible benefits of the rubber-modified system, such as increased skid resistance and noise reduction.
43 citations
TL;DR: A set of gravity models, one for each commodity category, has been developed to represent the commodity flows on a province‐wide basis and are acceptable as shown by statistical measures and commodity haul frequency diagrams.
Abstract: This study is based on a comprehensive commodity flow survey done in Alberta in 1977, which covered the full range of commodity flows by different modes of transportation. The survey data is grouped into specific commodity categories and a set of O‐D tables has been developed. The O‐D tables are the basis for the development of gravity models for commodity flows. A set of gravity models, one for each commodity category, has been developed to represent the commodity flows on a province‐wide basis. The gravity model for each category has been calibrated by an optimization technique that uses a power function and regression analysis. The calibrated gravity model is termed the “optimized gravity model” to indicate the new technique of calibration. The developed models are acceptable as shown by statistical measures and commodity haul frequency diagrams.
27 citations
TL;DR: In this article, the authors discuss the issues and research needs concerning the development of adaptive control logics for applications at isolated intersections, focusing on the information needs for adaptive control, the selection between a binary choice process and a sequencing process for timing adjustment, and future research needs.
Abstract: The effectiveness of conventional traffic-actuated control deteriorates rapidly as traffic volume increases. This problem can be alleviated through adaptive control. By monitoring vehicular movements an identifying the most likely short-term future flow patterns, adaptive control adjusts signal timings in an attempt to optimize signal operations. Both field test and simulation analysis have shown that adaptive control has the potential to provide improved signal operations. Further research is needed to develop a versatile and effective adaptive control logic that can replace traffic-actuated logics. The primary objective of this paper is to discuss the issues and research needs concerning the development of adaptive control logics for applications at isolated intersections. The discussions are focused on the information needs for adaptive control, the selection between a binary choice process and a sequencing process for timing adjustment, and future research needs. To be widely applicable, an adaptive control logic needs a vehicle-monitoring system that can provide reliable information and facilitate simulataneous use of real time and advance information for decision making.
24 citations
TL;DR: In this article, a laboratory and analytical research program was conducted to examine the effect of variations in test condition parameters on the resilient modulus, M sub r, and the IRM sub r.
Abstract: The index of retained resilient modulus (IRM sub r) is used to assess moisture-induced distress in asphalt concrete mixtures. The IRM sub r represents the ratio of two moduli and is sensitive to slight deviations in each measured value of modulus. A laboratory and analytical research program was conducted to examine the effect of variations in test condition parameters on the resilient modulus, M sub r, and the IRM sub r. In the laboratory test program, the strain and temperature dependencies of the M sub r were determined for a dense-graded asphalt concrete mixture. The results indicate that constant stress testing may result in a misinterpretation of the IRM sub r and further, tests conducted within the currently accepted temperature range may result in a +/- 20% deviation in the IRM sub r. In the analytical program, the effect of diametral test boundary conditions on the mesured value of M sub r was evaluated using two- and three-dimensional finite element models. The results indicate that the resilient-modulus diametral test is adequately represented by elastic theory based on an assumed plane stress condition.
21 citations
TL;DR: A mathematical model is described for estimating approach delays at pretimed, signalized, coordinated intersections, and this modeling concept represents a middle ground between bandwidth models that assume a constant flow rate in the dispersed platoon and TRANSYT‐like techniques.
Abstract: A mathematical model is described for estimating approach delays at pretimed, signalized, coordinated intersections. The delay models incorporate the size of and flow rate within the progression bandwidth. Platoon dispersion and secondary flows are considered via a simplified platoon‐dispersion algorithm calibrated from the TRANSYT‐7F model. The basic premise in this study is that traffic is assumed to arrive at the progressed approach in two average flow rates, one within the progression bandwidth, and another outside of it. This modeling concept represents a middle ground between bandwidth models that assume a constant flow rate in the dispersed platoon and TRANSYT‐like techniques where arrival flow rates vary in each time slice of the cycle length. The delay models are evaluated with Webster's delay formula for random arrivals and with simulated data in NETSIM; in both cases the results compare very favorably. Pending field validation of the delay estimates, an immediate application of the models is th...
TL;DR: In order to make the merging length calculation more generally applicable, the following need to be investigated: percentage of drivers who change lanes to allow vehicle to merge in different traffic and regional conditions; the possibility of including other important variables such as acceleration and deceleration rate, etc.
Abstract: The investigation is reported of the merging lane length needed for an improvement section between Kyoto South and Suita on the Meishin Expressway, Japan. A probabilistic theory for calculating the merging lane length was developed, and the theory was applied to the expected traffic and geometric conditions of the improvement plan. A series of traffic surveys were conducted to estimate the traffic flow characteristics of the merging lane and the drivers' behavior when they are merging with traffic at high speeds. It was concluded that the merging lane length for the transition section between the same directionally divided 4-lane section and the normal 3-lane section should be 700 m. However, in order to make the merging length calculation more generally applicable, the following need to be investigated: percentage of drivers who change lanes to allow vehicle to merge in different traffic and regional conditions; the possibility of including other important variables such as acceleration and deceleration rate, etc.; gap acceptance for the median side merging vehicle.
TL;DR: In this article, the strength development of three concrete mixes, with and without fly-ash, were subjected to many combinations of controlled moist and air-dry environments during the first 27 days.
Abstract: This paper reports on the strength development of three concrete mixes, with and without fly‐ash, subjected to many combinations of controlled moist and air‐dry environments during the first 27 days. Mix proportions and specimen fabrication technique were selected so as to reproduce roller compacted concrete construction for pavements, with the intent to determine the effect of curing on such applications. Wet‐dry curing cycles produce sizable moisture fluctuations in the samples; however, it is shown that apparently improper curing conditions do not cause drastic compressive strength reduction, but rather affect the concrete exposed surface layer. Fly‐ash inclusion seems not to alter the sample's compressive strength development as a function of the curing cycles.
TL;DR: In this article, a comparison between an urban grade separated interchange and an at-grade intersection in terms of the delay, vehicle operating cost, accidents, and vehicle emissions for several traffic demand levels was made.
Abstract: A procedure for evaluating the user benefits from highway improvement is demonstrated through a hypothetical case study. A comparison is made between an urban‐grade separated interchange and an at‐grade intersection in terms of the delay, vehicle operating cost, accidents, and vehicle emissions for several traffic demand levels. The results indicate that the urban‐grade separated interchange may be economically viable at an average daily demand as low as 40,000 total entering vehicles. Benefit cost ratios of 2.4 and 3.6 are generated with an initial average daily demand level of 80,000 total entering vehicles depending on the assumed traffic growth rate. A benefit/cost ratio of 2.9 is generated with an initial average daily demand of 60,000 total entering vehicles, assuming a 2.5 percent annual growth rate. Potential reductions in annual delay, fuel consumption, total vehicle emissions, and accident costs amounting to 73, 21, 40, and 80 percent, respectively, are indicated.
TL;DR: Examples of model results are described, highlighting the tradeoffs between the performance of the system during the perturbation period and the final equilibrium state, as well as the trade‐off between the schedule delay and the travel time experienced by system users during those periods.
Abstract: A dynamic simulation model is extended to represent traffic system disruptions in the form of lane closures. The model has two components: a macroparticle traffic simulator, and a user decisions component which comprises behavioral mechanisms governing the daily departure time decisions of commuters. The model is applied to the analysis of six alternative lane closure strategies associated with planned repair activities. Examples of model results are described, highlighting the tradeoffs between the performance of the system during the perturbation period and the final equilibrium state, as well as the trade‐off between the schedule delay and the travel time experienced by system users during those periods.
TL;DR: In this paper, the authors analyzed the performance of the prestressed concrete pressure pipe industry in the United States during the past four decades and found that the resultant prestress calculated by the present industry procedures correlates well with test results.
Abstract: Tests conducted by the prestressed concrete pressure pipe industry in the United States during the past four decades have been gathered and analyzed. The present industry design procedures are summarized. Test results are compared with design limits defined by AWWA C301 and these industry design procedures. The results show that the resultant prestress calculated by the present industry procedures correlates well with test results. Ratios of test loads that produce the first visible cracks, 0.005–0.010‐in. (0.13–0.25‐mm) wide cracks, the ultimate strength in three‐edge bearing load, and the burst strength of prestressed concrete pipe to the design limit loads are presented. The test results depict the ability of prestressed concrete pipe to control and limit crack width.
TL;DR: In this article, the impact of the number of consolidation points and special delivery requirements on various system performance elements was analyzed for a distribution system with a special delivery requirement level, defined as the portion of orders that must be shipped immediately without waiting for a specified holding period.
Abstract: The effect of recent deregulation of the transportation industry has been to increase the relative costs of small shipments in low-volume traffic lanes. Freight consolidation has been suggested as an effective way to reduce transportation costs and improve service levels for small shipments. Previous investigations of freight consolidation have been very general in nature and narrow in scope, even though the strategy has been suggested as useful for the design of a distribution system that deals primarily with small shipments. This paper focuses on an analysis of consolidation strategy and the impact of the number of consolidation points and special delivery requirements on various system performance elements. The special delivery requirement level is the portion of orders that must be shipped immediately without waiting for the specified holding period, thus resulting in a reduction of consolidated volume movements. The study indicates that consolidation can be used as a distribution strategy, with the prior knowledge that the level of special delivery requirement (priority shipment) can create a significant impact on system costs. The number of consolidation points, however, is not as critical to system performance as the level of special delivery requirement.
TL;DR: In this paper, the authors focus on the relationship between shear transfer capabilities across pavement joints and the effects on the behavior of the pavement and develop a numerical model that could accurately represent the mechanism for shear transfers across reinforced concrete pavement joints.
Abstract: This paper focuses on the relationship between shear transfer capabilities across pavement joints and the effects on the behavior of the pavement. The approach of the present study is to develop a numerical model that could accurately represent the mechanism for shear transfer across reinforced concrete pavement joints and implement it in an existing finite element code. That tool is then used for the analyses of various pavements for which experimental data are available; the model is further refined until the numerical results are in good agreement with the experimental information. This approach is employed for the interpretation of pavement behavior under different combinations of joint shear transfer conditions, asphalt concrete overlay thickness and material properties, and the influence of postpumping damage. The results obtained from this study are used for gaining a better understanding of how these various parameters affect pavement damage mechanisms and how such mechanisms would influence pavem...
TL;DR: In this article, the authors present an analysis and evaluation of vehicle flow characteristics on rural deceleration lanes using video photography, tape switches for transmitting speed information, and, for braking information, by hidden observers.
Abstract: This paper presents an analysis and evaluation of vehicle flow characteristics on rural deceleration lanes. Site observations were conducted by means of video photography, tape‐switches for transmitting speed information, and, for braking information, by hidden observers. Findings indicated considerable differences between commonly accepted assumptions of the AASHTO model for deceleration lane length determination and actual vehicle behavior. Major points include: (1) Average speeds of diverging vehicles at start of deceleration lanes were lower than average speeds of through vehicles; (2) deceleration values, for deceleration in gear and while braking, were lower than values suggested by AASHTO; and (3) average initial deceleration in gear lasted three times as long as the value currently assumed for design purposes. A model was then formulated to determine deceleration lane length, based on average freeway and exit ramp running speeds.
TL;DR: In this paper, the design of track structural components and foundations is based upon design loads higher than the nominal static values, and these design loads generally have been determined using dynamic impact factor.
Abstract: Design of track structural components and foundations is based upon design loads higher than the nominal static values. These design loads generally have been determined using dynamic impact factor...
TL;DR: In this paper, a method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented, based on results of familiar laboratory tests, and relatively simple methods of evaluating potential volume change are used.
Abstract: Problem subgrade materials consisting of collapsible soils are common in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used.
TL;DR: In this article, the authors review the areas where advanced technologies can significantly affect the way transportation engineering is practiced, along with strategies for implementation of the necessary changes in practice and the expected impact on civil engineering curriculum.
Abstract: Transportation engineering is a major component of the civil engineering profession. It involves planning, design, construction, maintenance, and operation of transportation facilities. Advanced technologies in the area of information systems, automation, and telecommunications have the potential of achieving cost savings and productivity improvements as well as enabling new developments in transportation. The purpose of this paper is to review the areas where advanced technologies can significantly affect the way transportation engineering is practiced. Strategies for implementation of the necessary changes in practice are also discussed, along with the expected impact on civil engineering curriculum. The emphasis of the paper is on surface transportation.
TL;DR: In this paper, a new adaptation of an existing finite difference solution to the problem of a plate resting on an elastic solid foundation is introduced (program FIDIES). Square elements are employed throughout the slab, and external distributed loads are converted to point forces applied at the center of corresponding grid squares.
Abstract: A new adaptation of an existing finite difference solution to the problem of a plate resting on an elastic solid foundation is introduced (program FIDIES). Square elements are employed throughout the slab, and external distributed loads are converted to point forces applied at the center of corresponding grid squares. Responses are calculated at the center of each plate element. Numerous convergence studies establish user guidelines with respect to required grid fineness. The accuracy of FIDIES is confirmed by comparison with closed‐form solutions, when available, an earlier finite difference solution, as well as these convergence studies. The effect of slab size is investigated for each of the three fundamental loading conditions, i.e., interior, edge, and corner. Predictive equations are derived for the latter two cases. These formulas, which were previously unavailable, highlight differences in behavior exhibited by the elastic solid and dense liquid subgrade idealizations.
TL;DR: In this paper, a detailed, accurate method for assessing air pollutant emissions from airport operations for the purpose of environmental assessment is presented, and a case study of an inventory for the planned addition of a runway to a medium-sized airport hub is followed throughout the discussion.
Abstract: This paper presents a detailed, accurate method for assessing air pollutant emissions from airport operations for the purpose of environmental assessment. Sources may include commercial aircraft, small general aviation aircraft, military aircraft, ground support equipment, stationary sources, fuel storage, fueling operations, and motor vehicles on the airport property. The methods used to estimate emissions for each of these categories are discussed and delineated. A case study of an inventory for the planned addition of a runway to a medium‐sized airport hub is followed throughout the discussion.
TL;DR: In this article, a dynamic analysis is used to predict stresses and deflections that develop when a moving wheel load is applied to predict fatigue failure criterion for a speed of 30 mph, which is the mean speed at the AASHO road test.
Abstract: When a truck wheel moves on the road, stress pulses develop within the pavement layers. These pulses are primarily functions of load magnitude, tire pressure, and vehicle speed. In this study, dynamic analysis is used to predict stresses and deflections that develop when a moving wheel load is applied. The method considers the inertial forces and assumes pulsating loads that accurately simulate actual wheel loading. The method is applied on AASHO road test sections to predict their theoretical response. The change of stresses and deflections at various loading times and at different speeds is computed and verified versus actual field data. Very close agreement was found between field deflections and theoretical predictions. The evaluated pavement response is used to develop a fatigue failure criterion for a speed of 30 mph, which is the mean speed at the AASHO road test. The use of accurate prediction models and valid failure functions may lead to better methods of design and rehabilitations of pavements.
TL;DR: In this article, an integer programming formulation and heuristic solution procedure for programming regional highway projects is presented, where the objective is to determine an optimal program of projects over a period of time.
Abstract: This paper presents an integer programming formulation and heuristic solution procedure for programming regional highway projects. The objective is to determine an optimal program of projects over ...
TL;DR: In this paper, a comparison of the two theories of the Marston load theory and the German design method for backfilled vitrified clay pipe design is presented, and it is shown that the load ratio depends significantly on the ratio of trench width to pipe diameter.
Abstract: In the United States and several other countries around the world, the Marston load theory is commonly used in computing the trench backfill loads on rigid pipes. Germany is using an alternative method developed by Abwasserbechnischen Vereinigung CoV. (ATV) as the working design method for rigid and flexible pipe. This paper presents the German design method and a comparison of the two theories as they are applied to buried vitrified clay pipe design. The load ratio is defined as the ratio of the German load to Marston load. This ratio shows that the Marston theory is conservative for small pipes backfilled with well-compacted granular material because it neglects the load relieving effect of the side fill and underestimates the friction between backfill soil and trench walls. The German design method is relatively simpler and could result in savings for vitrified clay pipe manufacture and design and for installation. The effects of the trench geometry, soil characteristics, the pipe diameter, and the stiffness ratio of bedding and Marston methods of design. Results show that the load ratio depends significantly on the ratio of trench width to pipe diameter. This paper would be of great interest to engineers in pipeline practice in their attempts to evaluate design techniques used in other technologically competitive countries.
TL;DR: In this paper, the durability and service life of concrete pipe culverts are discussed and the analysis of important enabling and triggering events that have caused or have the potential to cause the deterioration of concrete pipes.
Abstract: The durability and service life of concrete pipe culverts are discussed. The study reported includes the analysis of important enabling and triggering events that have caused or have the potential to cause the deterioration of concrete pipes. Regression analyses were used to produce prediction equations for the expected service life of culverts. The findings reveal an expected service life of 86 years. The service life reported herein may be of value to cost engineers performing life-cycle cost studies of these types of culverts. However, the prediction equations given should not be used to predict the service life of a particular culvert.
TL;DR: The results show that the new HCM delay model is sensitive to arrival type; thus it is important to know which arrival type to use in both isolated intersection and urban arterial environments.
Abstract: Delay is an important measure of effectiveness in traffic studies; it represents the direct cost of fuel consumption and indirect cost of time loss to motorists. The 1985 Highway Capacity Manual (HCM) used delay as the principal measure of level‐of‐service at signalized intersections. The manual introduced a delay model that is based partially on the traditional Webster model. The goals of this study were: (1) To review the delay models currently being used in the SOAP84 computer model for an isolated intersection and by the TRANSYT‐7F computer model for an arterial; (2) Compare them with the original model developed by Webster and the new model proposed by the HCM; and (3) assess the HCM model in both isolated intersection and urban arterial environments. The results show that the new HCM delay model is sensitive to arrival type; thus it is important to know which arrival type to use. The delay values calculated by the new HCM model, SOAP84, and TRANSYT are close to the values resulting from NETSIM.
TL;DR: In this paper, the optimal parking angle for maximizing lot capacity is approximately 70 degrees and the field tests also showed that the 70 degree layout is preferable to the 90 degree layout in terms of parking maneuverability and safety.
Abstract: This is a reexamination of the optimal parking angle using mathematical analysis and field tests. The angle usually recommended for parking stalls (relative to access aisles) is 90 degrees. Mathematical analysis is presented which indicates that the optimal parking angle for maximizing lot capacity is approximately 70 degrees. The field tests also showed that the 70 degree layout is preferable to the 90 degree layout in terms of parking maneuverability and safety.