The models developed for traffic forecasting in the Helsinki Metropolitan Area, Finland, are presented. The basic traffic surveys for the Helsinki Metropolitan Area Transportation Study 1988 were done during 1987 and 1988. The main field studies were an origin-destination (OD) survey of automobile traffic, an OD survey of public transport, and a personal trip diary interview. Modelling of only internal trips made by inhabitants of the metropolitan area is described. The modelling was based on the trip diary interview. The model structure was basically a four-step model with feedback between the last three steps. Trip generation was calculated using production and attraction rates. Mode and destination choice were mostly modelled using nested logit models. In network loading, a standard multipath equilibrium assignment model (EMME/2 system) was used. Trips were divided into four categories according to trip purpose (home-based work trips, home-based school trips, other home-based trips, and non-home-based trips). Four alternative modes were included in the mode choice models. The population was divided into categories according to the different steps of the modelling. The most important categorisation was the division according to a person's access to a car. Destination choice models included 117 alternative destinations. The coefficients of mode choice models were logical and the variables predictable. The first destination choice models had some theoretical deficiencies, which were partly abolished using constrained estimation. The model system with unconstrained models produced satisfactory forecasts. New models will be estimated and new forecasts will be made during 1992.
Abstract