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The temporal transferability of mode choice and trip distribution models was studied by using the data based on traffic surveys in the Helsinki, Finland, metropolitan area in 1981 and 1988. The updating procedures examined were the Bayesian updating, combined transfer estimation, transfer scaling, and joint context estimation procedures. The results of model updating indicated that finding the correct method and sample size for each case is not an unambiguous task. The best method depends on the difference in model coefficients between the initial and the final stages as well as the quality of the data. According to the statistical tests, no differences could be discerned between the models at all. However, the sample enumeration test proved that the models’ ability to predict changes in behavior can vary greatly according to the method used. On the basis of this research the transfer scaling seems to be the method best suited for simple models. In particular, the method is quite useful if the transfer bias is large. The combined transfer estimation procedure performs best when there is a great number of observations and the transfer bias is small. With small sample sizes the Bayesian approach and the joint context estimation give the best results.

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The main goal of this research was to update the basic saturation flow values of signalized intersections. The secondary goal was to analyze the effects of certain external factors (such as weather, road, and traffic conditions) on saturation flow. The updating is based on extensive field measurements and simulations. Altogether, about 39,000 queues were observed in this study. Field measurements at 30 locations were made according to the method described in the Highway Capacity Manual and simulations were done with the Helsinki University of Technology HUT-SIM simulator, which was calibrated and carefully validated for Finnish road conditions. A summary of calibration parameters is also presented. The new base value for straight-through lanes is 1, 940 vehicles per hour; the previous value was 1, 700 vehicles per hour. In general, the updated saturation flow values of different lane types are 5 to 20 percent larger than the previous base values. The saturation flow models of different lane types are described. The effects of geometric and traffic composition factors, such as percentage of turning vehicles, traffic composition, lane width, and approach grade, were examined and modeled. Effects of weather, road surface, light conditions, and speed level were also analyzed. The drop in saturation flow was about 20 to 30 percent under slippery road and snowy conditions. In rainy conditions, the drop was smaller, about 10 percent. The effect of speed on saturation flow is also described. The most important results of this 2-year project are the saturation flow values for different lane types, knowledge of the effect of external factors (especially during winter), and the large database, which can be used for other purposes. The possibility of using special signal control programs under bad road conditions is discussed. With these kinds of programs, better safety and higher capacity can be achieved.

A combined revealed preference (RP) and stated preference (SP) survey that was done in the Helsinki, Finland, metropolitan area to reveal the importance of different level-of-service (LOS) factors in public transportation is described. The study was done as a route choice survey between origin-destination zone pairs with two route alternatives that had differences in total travel time, number of transfers, possibility of getting a seat, walking and waiting times, and fare. A separate SP game of transfer environment was also done. The SP study was undertaken among the RP respondents. The levels of the SP attributes were tailored according to the trip in the RP survey. The RP and SP data were analyzed together using structured-tree-type logit models to adjust the variances in different data sets. According to the study results one transfer equals about 10 min of door-to-door travel time, and passengers are willing to travel 15 min longer to get a seat for the trip. The experiences from the use of a tailored postal survey in a SP study were quite positive. However, regardless of study method a very careful definition of the attributes and attribute levels is needed. The results of the survey are quite in line with other similar studies reported in the literature and give an estimate of the passenger response to the public transportation LOS attributes included in the study.