The development of "expert systems" for microcomputer applications has received increasing attention in the transportation engineering field. Expert systems are computer programs that include simulations of the logical reasoning and problem-solving processes of human experts for specific applications. Proper implementation of this concept offers a possible means to effectively use the specific knowledge and experience of recognized professionals, efficiently use limited highway resources and revenue, and provide safe, efficient transportation programs. The major advantage of expert systems is that they permit specific human knowledge used in the decision-making process to be systematically examined, organized, and applied to particular engineering problems. During the typical intersection design process, highway engineers make many decisions concerning the operationaleffectiveness and trade-offs among a number of design factors. These important decisions may be bounded by either the planning budget, the potential total project costs, the maximum lane width of each typical highway lane, or the potential traffic demand volumes. This study illustrates the prototype applications of expert system design and lisp programming in the highway design process using the autocad (trademark) package. Autolisp (trademark), a version of lisp supported by autocad, was used to create a small-scale expert system to interface with the normal drawing functions. This study demonstrates the feasibility of implementing built-in functions of the autocad system through autolisp programs to assist end users in completing the decision making for potential highway design applications. This paperappears in transportation research record no. 1239, Geometric design and operational effects.
Abstract