Tsuna Sasaki

Estimation of origin-destination matrices from link traffic counts on congested networks

Conventional methods for estimating origin-destination (O-D) trip matrices from link traffic counts assume that route choice proportions are given constants. In a network with realistic congestion levels, this assumption does not hold. This paper shows how existing methods such as the generalized least squares technique can be integrated with an equilibrium traffic assignment in the form of a convex bilevel optimization problem. The presence of measurement errors and time variations in the observed link flows are explicitly considered. The feasibility of the model is always guaranteed without a requirement for estimating consistent link flows from counts. A solution algorithm is provided and numerical simulation experiments are implemented in investigating the models properties. Some related problems concerning O-D matrix estimation are also discussed.

The equilibrium-based origin-destination matrix estimation problem

This paper examines a model due to Nguyen for estimating origin-destination (O-D) matrices from observed traffic flows on each network link. It is shown that the previous bilevel optimization models for choosing an O-D matrix can be transformed into single convex programs. Under the condition that the observed link flow pattern is an equilibrium, Nguyens model is demonstrated to be equivalent to an underspecified system of linear equations with non-negative variables. By exploiting the properties of the systems feasible region, simpler methods, such as a least squares technique, can be used to obtain an O-D matrix that, when user-optimally assigned to the network, reproduces the observed link flows.

Estimation of time-varying origin-destination flows from traffic counts: A neural network approach

A dynamic model based on the error back-propagation learning principle in neural network theory is proposed for estimating origin-destination flows from the road entering and exiting counts in a transportation network. The origin-destination flows in each short time interval are estimated through minimization of the squared errors between the predicted and observed exiting counts which are normalized using a logistic function. Two numerical experiments are conducted to evaluate the performance of the proposed model; one uses a typical four-way intersection, and the other one uses a real freeway section. Numerical results show that the back-propagation based model is capable of tracking the time variations of the origin-destination flows with a high stability.

AN OPTIMAL LAND USE DESIGN MODEL WITH TRAFFIC CONGESTION

Abstract Given a transportation network, a land use design model is formulated as a two level system optimizing problem. The master problem allocates land use activities in zones so that the sum of the total development cost of land use and total transportation cost would be minimized. The sub problem gives a traffic flow equilibrium through combined trip distribution and assignment procedure. Taking into consideration traffic congestion, travel cost between each origin and destination pair is endogeneously determined. Consequently land use allocation, trip distribution and assignment process are consistent in the model. The meaning of the problem is stated from the view point of game theory, especially the Stackelberg game whose players are the planner and the network user. Heuristic solution procedure is proposed using MAP algorithm. A numerical example is executed for a simple and hypothetical zoning and transportation network. Some extensions of the model is briefly discussed.

DESIGN OF STREET SIGNS IN KYOTO

街並みの景観を構成する変動要素の一つである商業サインは, 商業情報を記号として伝えるだけでなく, 特化した形態や色彩の意匠が, 街のイメージ形成に大きく影響を及ぼすことがある. 本研究は, 先斗町, 北山通りなど京都の新旧を代表する商業ストリートの中で, とくにその道らしさを表現する商業サインを抽出し, その意匠を評価した. そして, 各通りに共通するデザインの基調を考察し, サインが形成するメディアイメージを推察した.

Light and Shadows of Tivoli Park and the Parc de la Villette

Some examples of increasingly rare and beautiful light and shadows can be found in the urban parks. Their atomsphere is based on exceptional compositions of gardens, paths and amusement facilities. In Tivoli Park and the Parc de la Villette beautiful shadows are formed by unseen patterns and devices that take into account the cultural climate and urban life.The purpose of this study is to clarify and summarize the samples taken from actual two parks with an eye. We also try to make the design characteristics (arrangement of space and material, etc.) clear.