Increasing computer power and continued developments in software have resulted in easier access to dynamic assignment packages in practice. However, in reality there are many existing static network models, which represent a high level of investment (in terms of data and staff expertise). It would be desirable to use this investment by converting static models to equivalent dynamic representations, aiming to maintain the main inputs and to stay close to the level of calibration achieved with the original, static model (at least at the time-aggregate level). Hence, conversion procedures are required. Hague Consulting Group is involved with two projects that require conversion of static to dynamic representations, encompassing two static models (TRIPS and QBLOK) and three dynamic models (CONTRAM, 3DAS and DYNEMO). The paper starts off with a discussion of the conceptual differences between static and dynamic model representations (related to, e.g. the possibility of over-capacity and queuing). Mathematical procedures have been developed to convert, in particular, speed-flow-density relationships that govern the representation of congestion. These are elaborated in the paper. Attention is paid to the enhanced input requirements of dynamic models, including time-dependent OD matrices at the 5-15 minute level. Empirical departure time profiles have been estimated at the quarter-hour level from National Travel Survey data; these are presented. Initial comparative results of the application of equivalent static and dynamic representations are given. Recommendations for practice are made.
Abstract