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An algorithm for control of queue lengths at oversaturated intersections oriented towards delaying spillback across upstream intersections as long as possible is described. It is based on determining the change in queue and the allotment of available green time so as to keep the ratio of the actual queues to the maximum link storage space on both phases equal. The mathematical development of the algorithm is described in terms of a Z transform analysis, and the conditions for stability are derived. The resulting mathematical model is linear with the exception of a saturation type nonlinearity caused by the physical requirement to limit split. A describing function analysis is used to demonstrate loop stability in the presence of the nonlinearity.

The queue control algorithms that are commonly used by ramp-metering controllers often permit the queue to extend a considerable distance upstream of the queue detector on the ramp. This detector senses the presence of a queue with the intent of preventing queue spillback onto the surface street or intersection that is located upstream of the ramp. Queue control is usually obtained by switching between the desired metering rate and a higher metering rate. In some cases metering is terminated. This type of limit cycle control often results in considerable variation in the length of the queue, even for a constant average vehicle arrival rate at the ramp. This high-amplitude limit cycle operation is indicated, by simulation, to result from the relatively long detector sampling and computation period (typically 1 min) that is commonly used. A control algorithm using a 10-sec sampling period is indicated to substantially reduce the limit cycle amplitude. Performance is further improved when the control algorithm anticipates the buildup of the queue over the spillback detector.

The authors examine the relationship between retention and changes in freshmen's perspectives on social and academic issues. Using data collected from a student questionnaire administered at the beginning and end of thefieshman yea?; the authors found that contact with faculty may play a signtficant role in how freshmen view their college experience but may not be related to retention. Student retention ?nay be only indirectly related to changes in social and academic integration at an institution and may depend more on variables associated with student characteristics and predispositions.Academic advisors are in a unique position to discern the personal and educational changes in students during the first year in college. These changes have been linked to the need to design programs and services for the freshman year experience in order to facilitate certain desirable freshman outcomes. Although first-year students bring certain individual characteristics to college (e.g., family background, high school experiences, race, and academic aptitude) that certainly affect their first-year experience, some models of student change emphasize the role of the institution and the impact of student interaction with the college environment. These models emphasize how students act and think while involved in that environment (Pascarella & Terenzini, 1991). This personenvironment fit has a direct and indirect effect on whether the student persists or drops out.Tinto's theory of student departure (1987) seeks to explain why students voluntarily withdraw from college. Tinto emphasizes that the way freshmen react to their new environment not only depends on their precollege schooling and background but also on their initial intentions about graduating from college and other personal goals. Student integration into the academic and social systems of the institution is viewed as critical to continuing matriculation. Academic integration can be measured by student academic performance and by their level of intellectual development; social integration can be determined by the extent and quality of student interactions with their peer group and the faculty. According to Tinto, the greater the level of social and academic integration, the greater a student's subsequent commitments, both to the institution and to the goal of college graduation.Many research studies have substantiated Tinto's model of student departure (Allen,