This paper presents a method for estimating freeway travel times in real time directly from flow measurements, which is desirable for present and future Intelligent Vehicle-Highway Systems (IVHS) applications. An inductive modeling approach adapted here is based on stochastic queuing theory and the principle of conservation of vehicles. The analytical expression for link travel times satisfies traffic dynamics where the new form of the conservation of vehicles has been derived under generalized traffic conditions. A computer program has been developed to implement the algorithm. Analysis results show that the estimates have good agreement with empirical data measured at 30-s intervals. This methodology has potential applicable to automatic traffic control and automatic incident detection.

Busways are controlled-access facilities dedicated for bus service separated from general traffic. The concept of busways was first given serious consideration in the 1960s; however, only a few of them have been constructed in North America. This paper examines the potential of busway transit in providing urban environments with cost-effective mobility. The review makes the case that there are some misconceptions concerning the cost and level-of-service characteristics of busways. In the final section, a comparison is made between busways and their most prominent competitor, light rail. The comparison is done in the framework of the four most cited advantages of light rail, and concludes that busways, in most cases, are likely to be a superior mode of transit to light rail.

This research examines composition, weather, and time-of-year count variability for a longitudinal bicycle count program. The results indicate greater variability in the PM peak period than in the AM peak period, and this variability is at least partially attributable to the presence of nonutility cyclists. Second, all locations display the same functional form for count volume by both temperature and amount of precipitation, and it appears that temperature may be a better predictor of volume than the amount of precipitation for these data. Third, the results of a Poisson model statistically confirm many of the factors thought to influence cyclists, and identify that a single count volume may be biased by as much as ±15% depending on the time of year in which the count was undertaken. Finally, a new bicycle functional classification system based on PM peak-period composition is proposed.

Accidents continue to occur on our transportation facilities. People injured in these accidents continue to file lawsuits against transportation agencies, in part because the language used in published standards for design and maintenance contain deficiencies. Risk management is the organized approach to preventing or reducing lawsuits. Past risk management research has focused almost exclusively on identifying the physical characteristics of a road that are most often the subject of lawsuits. No attention has been given to the question of whether the language of design standards influences the frequency of lawsuits. This author suggests that written design standards be reviewed and possibly redrafted to reduce the frequency of lawsuits. Language in design standards that is clear, objective, quantifiable, reasonable, and qualified will best serve this goal. When engineers choose to deviate from published standards, a written explanation for the deviation should be prepared.

A study of guardrail end accidents on the Oklahoma State Highway System (1988–91) examined the severity of exposed and turned-down guardrail end accidents in relation to the type of end, vehicle weight, and vehicle rolling and/or vaulting. The data showed that lightweight vehicles and turned-down ends were associated with increased rolling and/or vaulting. Rolling and/or vaulting was associated with increased accident severity. A direct interaction among end-type, vehicle weight, and accident severity was not present; however, the interaction among end-type, vehicle weight, and rolling/vaulting was statistically significant. In terms of the resulting injury and death, the overall performance of the turned-down ends was no better than the exposed ends that they had replaced.

Bus transit systems provide a valuable service to many residents living within urban areas. Like other vehicles, buses depend on paved streets and roads for a smooth ride. The pavement wear due to truck traffic has been monitored and researched for many years. The effects of urban transit buses on pavements owned and maintained by local governments are examined from the following three perspectives: (1) Pavement design; (2) pavement condition data analysis; and (3) visual observations. Each of the three perspectives suggests that significant pavement damage is caused by transit bus traffic. Another analysis probed pavements' damage if buses had a third axle. There are a number of significant conclusions offered which include the following: (1) Fully loaded transit buses exceed the California legal axle limit; (2) the construction cost to accommodate transit buses is approximately 5% for arterials and 58% for collectors; (3) the addition of a third axle will reduce the pavement damage by approximately three times; and (4) another approach to reduce pavement damage would be to use lighter-weight materials in the manufacturing of transit buses.

The trip making process using transit versus private automobile differs in the use of time schedules, walking paths, transfer stops, plus issues such as fare and safety. Due to these factors, many of the standard shortest path algorithms do not apply. The purpose of this study is to develop an algorithm and strategy for transit providers to find best alternatives for the user, and to demonstrate how a geographic information system can be used in the development of transit advanced traveler information system (TATIS) to meet these needs. This paper presents a short introduction to TATIS systems, some commonly used algorithms in determining the shortest and multiple paths, and a new strategy that was developed in this study which differs from standard network algorithms. The major features of this proposed algorithm are: (1) Capability of handling multiple modes of transit; (2) providing paths that include walking distances from and to the transit path as well as between transfer points; and (3) provision of multiple optimal paths to allow the user flexibility in choosing a path.

State Transportation Departments nationwide manage huge amounts of information. Examples include geometric plans, sign inventories, maintenance records, engineering studies, and so on. In many cases, no indexing or archiving system is available for storing and retrieving this data. A prototype computer-based model was developed in order to address these indexing needs. The model focuses on engineering report tracking but can be extended to accommodate other types of information. The model is based on a procedure that links signalized intersections and road segments to nonspatial attribute data in a Geographic Information System (GIS) environment. A paper form was developed in order to facilitate the extraction of data from engineering reports. The indexing model also includes a computerized version of the paper form to assist in data entry, and another form for query purposes. The indexing model was applied to 10 years of engineering report data from East Baton Rouge Parish, La.

This paper uses simulation to assess intersection performance under enhanced vehicle-actuated signal control. The enhanced strategies seek to: (1) terminate green time in such a way as to promote use of the clearance interval by discharging vehicles; (2) shorten the required duration of the clearance interval by only serving, to the extent possible, queued vehicles; and (3) respond to gaps in individual travel lanes. Enhanced schemes are compared with conventional policies for an array of operating scenarios. Findings suggest that substantial reductions in vehicle delay result from use of the enhanced strategies.

The power spectral density (PSD) estimate is a parameter commonly used to characterize the acceleration of vehicles and, in conjunction with closed-loop random vibration controllers, to simulate the transport environment. The vertical acceleration experienced by the loading tray of road transport vehicles is mainly a function of the type of suspension, load, vehicle speed, and road surface characteristics. While the first three parameters may vary considerably between and during journeys, the statistical parameters used to describe road surface profiles are much less susceptible to change with respect to time. This paper presents a brief analysis and discussion of the spectral and statistical characteristics of actual road surface elevation records. The deviation of the road profile distribution from the Gaussian distribution is revealed, and it is shown that roads of different roughness seem to retain their spectral shape. In addition, a range of statistical parameters are introduced and recommended for use in the classification of road profiles. A technique in which a random vibration controller is used to simulate road profile spectra by controlling the displacement instead of the acceleration of a shaker table is demonstrated. The technique uses a physical model of a vehicle suspension to account for the dynamic characteristics of the vehicle. Finally, the use of digital signal processors (DSP) together with a time domain adaptive filter control technique for the accurate reproduction of synthesized demand signals is presented.

This paper describes the development of a computer model (known as PAVENET-R) based on genetic algorithms, an optimization tool capable of overcoming combinatorial explosion, to solve the pavement maintenance-rehabilitation trade-off problem at the network level. The formulation of the PAVENET-R model is described in detail. An integer coding scheme is selected for parameter representation in the model. Two genetic-algorithm operators, namely the crossover operator and the mutation operator, are used. A “change table” encodes constraints to the genetic-algorithm operations to ensure that only valid offspring are generated from a parent pool. Four numerical examples of road networks of 30 pavement segments, each with different relative costs of rehabilitation and maintenance activities, are analyzed to demonstrate the trade-off relationship between pavement rehabilitation and maintenance activities. The detailed maintenance and rehabilitation schedules of the solutions, and the convergence characteristics of each solution are presented.

In this paper, the writers present a formula for sizing steel pipelines of optimal diameter with equally spaced, similar pumping units. The general case of an inclined pipeline with fitting is considered in the analysis. The sizing formula is based on a friction-factor formula that spans through all the flow regimes of the Moody diagram. Although the formula is implicit, the final solution is attained after a limited number of trial cycles. A simple computer program carries out design calculations and provides the optimal pipeline size as well as spacing between pumping units. Solved numerical examples are provided to demonstrate the simplicity and practicability of the proposed technique.

The flow capacity of existing sanitary and storm sewers is a significant issue when making decisions on the optimal method of rehabilitation. At times the resulting flow capacity is an important factor during the design of a sewer rehabilitation program. In the United States, the flow capacity is usually determined using the Manning formula, which includes the empirical parameter n. This committee report discusses the principal elements of the Manning formula, coefficient and field variables that contribute to the selection of values for n, and provides typical values for n for mature sewers in need of rehabilitation and for mature sewers rehabilitated with many currently available rehabilitation materials. The report then discusses a rationale for selecting a design n within a range of values and predicting the resulting change in flow capacity of the sewer. A field example is given where n values were measured. The report is intended to provide guidance to engineers making decisions related to rehabilitation of gravity flow sewers.