An experimental knowledge‐based expert system to assist in traffic signal setting for isolated intersections is presented. In contrast to existing computer aids, the system can be applied to intersections of highly irregular geometries. Algorithmic processes to evaluate signal settings and decision tables to identify traffic flow conflicts are invoked by the expert system; phase distribution of flows is performed by applying heuristic rules. The system was written in the OPS5 expert system environment. Advantages and disadvantages of the expert system programming approach relative to conventional algorithmic processes in the traffic engineering domain are described.

The expert system is a relatively new application of artificial intelligence technology that is beginning to emerge in the field of civil engineering. This new computer‐aided tool has the potential to significantly affect the way today's civil engineer assesses and solves complex problems. An expert system named CHINA (Computerized Highway Noise Analyst) has been developed that is capable of interacting with an existing FORTRAN model that aids an engineer in acoustically designing a highway noise barrier. CHINA executes the design model, interprets the results, and decides if those results are valid. If they are not, CHINA determines new input parameters and re‐executes the design model until a satisfactory design is obtained. Three actual highway noise abatement problems are examined in detail and the design solution from CHINA and a human expert are compared. The results of this comparison indicate that CHINA is capable of designing highway noise barriers that are at least equal, in terms of performance and cost, to those designed by a human expert. Thus, the concept of using expert systems as an expert advisor, or as a colleague to a human expert, is demonstrated to be feasible in this application.

Increased automation of air traffic control (ATC) systems appears to offer a solution to the dual problem of handling higher levels of air traffic while reducing the costs incurred by the ATC system itself and the aircraft under control. Because of the complexity of the ATC system, expert systems may provide a valuable addition to human decision making and conventional data processing in the design of future ATC systems. A number of potential applications, including traffic flow management, controller support functions, system failure management, training, and system configuration planning, are described, and the special requirements of expert systems developed for realtime control applications are discussed. The structure of a prototype expert system to assist in air traffic flow management is described. The paper concludes with a brief examination of the potential for applying similar techniques to other transportation control systems.

Pavement surface condition data play a pivotal role in the analysis and design of pavement rehabilitation strategies. In project design, this information is usually used by a limited number of pavement engineering specialists who apply experience and judgment to formulate design and investment decisions. The nature of this process resists computerization using conventional computer tools. The development of a knowledge‐based expert system that is based on programming concepts from the field of artificial intelligence is described. The system is called SCEPTRE, and assists highway engineers in planning cost‐effective flexible pavement rehabilitation strategies at the project level. The use of an expert‐systems approach permits SCEPTRE to make its specialized body of knowledge accessible to a much broader range of potential engineering users.

The concept of timed transfer, a scheduling procedure used in transit systems, is explained and examined. In particular, the feasibility of this procedure is evaluated using a simple two‐route case to determine the conditions under which timed transfer provides improved service levels compared to unscheduled transferring. A computer program is developed, which simulates four transfer strategies: (1) unscheduled transfers; (2) scheduled transfers without vehicle waiting; (3) scheduled transfers where the lower frequency bus is held until the higher frequency vehicle arrives; and (4) scheduled transfers when both buses are held until a transfer event occurs. The factors affecting timed transfers are evaluated based on an analysis of simulation results and the development of regression models. Preferred strategies for different route conditions are subsequently described.

Work has been done to develop a rating system for priority planning use with secondary roads. A key constituent of the rating system is the design standard. It provides the basis for several rating criteria used to evaluate a given road for inclusion in road improvement programs. Therefore, choice of relative design standards can have a significant effect on a rating. Design standards commonly used for secondary roads are similar to those adopted for primary roads with concern for traffic volume and travel speeds. However, this does not necessarily reflect the principal use of these roads as collectors and local access. Emphasis should be on accessibility, and travel speed is less important a factor. Use of lowered design speeds is proposed as one way to economize by avoiding higher costs associated with improved alignment, wider roadways, and flatter ditch slopes. Possible effects on tort liability are reviewed and sample standards are described.

Highway rigid pavements, such as many of the constructed facilities of the nation, have been deteriorating, some even beyond functional failure, due to excessive loading, environmental effects, and chemical attack of the material components. A method to estimate the mechanical deterioration of highway rigid pavements caused by repetitive traffic loading is presented. In the method presented here, erosion, fatigue, and joint faulting are recognized as mechanisms of failure in highway rigid pavements. A nonlinear analysis with finite elements is used to calculate the repetitive stresses and strains caused by traffic. Decay of slab stiffness and load transfer efficiency, as well as pumping and amount of damage, are obtained as a function of traffic volume and pavement properties.

A study was conducted: (1) To collect accident, environment, geometric and traffic flow data at rural three-leg wye intersections in West Virginia; (2) to identify any patterns linking accident data and intersection characteristics; and (3) to develop a measure of intersection hazard to be used in establishing priorities for improvement. Regression models, constructed to predict accident rates as environmental, geometric and traffic conditions changed at the intersection, did not prove to be statistically significant. A systematic approach to developing a specific Intersection Hazard Index was suggested. A primary advantage of the index is that it can be computed from data in an accident records system. In addition to including accident rate, the index also gives extra weight to intersections having concentrations of accidents in particular locations or accident type categories. Additional refinements to the index were recommended.