Basil Psarianos

Induced Traffic Prediction Inaccuracies as a Source of Traffic Forecasting Failure

Abstract In this paper, evidence from the literature on the inaccuracy of forecasts from transport planning models is presented and its impact on capital infrastructure planning decision-making is demonstrated. Empirical evidence suggests that forecasts used for major planning decisions have been found to be rather inaccurate (when comparing forecast volumes with actually realized volumes after time passed). A meta-analysis of the relevant literature provides insight into the expected magnitude of these deviations as well as the main contributing factors, including induced demand.Furthermore, evidence of these irregularities in the case of two major expressway infrastructure projects in Southern Greece is presented, providing insight about a typical example of a country with a developing freeway network. Data from the immediate impact zone of the Attica Tollway in the metropolitan area of Athens and the neighboring interurban Elefsina-Korinth motorway are used to demonstrate that the projects resulted in considerable changes in the land use patterns and density, both in terms of residential and commercial development, resulting in the generation of additional traffic flows.Having demonstrated the need for re-thinking how long-term traffic is forecast, suitable recommendations for promising directions are made. Dealing with uncertainty is one key aspect that can be easily incorporated to existing forecasting tools. Furthermore, the need for more detailed and area-specific models, e.g. through the integration of activity-based modeling, specific mobility patterns and demands are also outlined.

Generic Methodology for 3-D Available Sight Distance Calculation

The objective of this paper is to develop a generic mathematical methodology that can carry out the available sight distance calculation of a roadway directly in three-dimensional (3-D) space and in a fully automatic manner. The presented methodology overcomes the conventional approach of studying the 3-D road configuration separately and sequentially in its horizontal and vertical alignment. As far as the road surface is concerned, it is modeled as a 3-D B-spline surface. Moreover, the road centerline as well as the right and left borderlines which play a crucial role in the sight distance calculation are mathematically defined by modeling them as 3-D B-spline curves; therefore, their mathematical formulation is well determined. In addition, the cut and fill slopes of the road are also modeled as 3-D surfaces, and finally, the road surface and its corresponding cross sections are realized as one strictly defined and unified 3-D mathematical surface. This is particularly important since integrated 3-D geometric information is obtained, meaning that all calculations are applied in the real 3-D space where the road construction actually exists. Eventually, all the concepts that are incorporated in the respective equations and formulas are applied in the natural 3-D geometry of the road surface. The main competitive advantages of this methodological approach compared to other 3-D models proposed, is that the whole 3-D geometric information of the road construction is taken into account, and additionally, the available sight distance can be calculated for any potential trajectory followed by a vehicle. In addition, the methodology allows for universal adjustment that is not constricted by regional idiosyncrasies (i.e., existing design guides and policies). Finally, the computational part of this methodology is attained by expressing the functions in code through the programming language offered by the software Mathematica, whereas the whole process is demonstrated as a case study. It is noted that all the algorithms and codes appear in a fully automatic manner and parametric form, allowing the user each time, to set the corresponding and required input values to the algorithm.

Powered two-wheeler rider eye-height determination

Abstract Vehicle driver and powered two-wheeler (PTW) rider eye-height (EH) is one of the key factors in highway design, as it can determine sight distances, which is a key factor in geometric design. Different vehicle types and driving conditions can affect the EH. While a large number of studies have focused on the determination of passenger car and truck driver EH, only a small number of studies have attempted to determine the EH of two-wheelers. The objective of this research is to investigate the parameters that affect PTW rider EH and determine appropriate values. A multiple-camera experimental design was developed for the measurement of PTW EH. Two arteries with different characteristics (one freeway and an urban arterial) were chosen for the data collection. The collected data are analyzed and conclusions are drawn regarding the rider EH for different PTW types and classes using analysis of variance (ANOVA) and the Tukey “honest significant difference” (HSD) method. The relation between EH and speed is specifically investigated and it is concluded that rider EH is not negatively correlated with PTW speed. Directions for future research are outlined; these include additional studies under different conditions the collection of richer data sets (e.g. including data on the riders and the PTWs).