Traffic Planner Research Articles

Booking cum rationing strategy for equitable travel demand management in road networks

Trip booking and traffic rationing have been proposed as two alternative travel demand management (TDM) strategies over the last two decades. Through artificially restricting demand (vehicle travel) by booking or rationing the scarce road capacity during the peak periods, the negative externalities generated by travel demand over available supply or road capacity can be reduced. In many cases, the two strategies also have the main goal of reduction of air pollution. Trip booking system allows vehicles/drivers to reserve prescribed areas or some lanes/segments of freeways/roads for their use during specific time periods, thereby maintaining a certain level of service of the roadway space. It is often in the form of a permit to control the number of reservations issued. On the other hand, traffic rationing is often achieved in reality through restricting access into an urban cordoned-off area or city center based on the last digits of the license number on pre-established days and during certain periods, usually the peak hours. However, theoretical studies and practical implementation of the two strategies have been conducted separately. Taking their advantages, this paper proposes and demonstrates a novel hybrid strategy of booking cum rationing for efficient and equitable TDM. We show that the problem of interest can be simply formulated as a convenient linear programming problem in a general network. Simple examples are provided to elucidate how this hybrid strategy can achieve a traffic flow distribution pattern prescribed by the traffic planner while maintaining the fairness, efficiency, and flexibility of individual choices.

Urban Transportation Planning Influences and Legacies: Kurt Leibbrand, Germany's Acclaimed Postwar Traffic Planner

This article explores several dimensions of the work and career of Kurt Leibbrand, often considered the most influential German urban transportation planner after 1945. It examines some key ideas prevalent in his publications, such as his advocacy of the priority of transportation planning, hostility to citizen participation in planning, and rejection of pedestrian zones. In assessing his status, the paper discusses his contributions to traffic plans for the cities of Basel, Mainz and Selb. The paper also examines some shifts in his career, including his move to the Swiss Federal Institutes of Technology in 1950 and his resignation there after his arrest for having ordered the murder of Italian volunteers in his army unit during the war. Leibbrand was convicted of manslaughter but not punished because the statute of limitations had expired. He continued to work as a consultant but did not again hold an academic position in the German-speaking world.

Design of Traffic Circulation Systems to Minimise Conflict

At first sight, it might appear that the traffic planner faces an impossible task, trying to adapt the road network to accommodate the needs of road users traveling between different origins and destinations in a tangle of conflicting—and continually increasing—demands. During the 1960's, Professor Reuben Smeed and his colleagues adopted a radical approach. In their studies of urban movement, they pictured the network as a continuum, and using analytical methods, gained valuable insights into the properties of road systems, including their potential capacity for delivering commuter traffic to the city centre. Today, this work takes on a new practical relevance. Electronic route guidance and road pricing technology allow roads to be managed in a proactive fashion, routing vehicles so as to get the most out of the available road space, in other words, adapting the traffic to the network rather than the other way round. However, the continuum approach is suitable only for larger cities. In this paper, we review a related area of work in which the road links and junctions, albeit connected in an idealised and regular fashion, are represented as discrete entities. In principle, the results are applicable to smaller towns where the ‘grain’ of the network has an important bearing on what can be achieved.

Personal noise ranking of road traffic: Subjective estimation versus physiological parameters under laboratory conditions

Objective To evaluate the subjective estimation of noise-induced discomfort and its correlation to psychoacoustic and physiological parameters under laboratory conditions. To establish an effective description of sound qualities of road traffic noise, supplementing the current standards and calculation specifications. Methods Pass-by vehicle noise samples were binaurally recorded with a dummy head measurement system, and synthetically composed to six vehicle ensembles considering different road beds, varying speed profiles and noise barriers. Fifty-one persons were selected and tested under laboratory conditions. Study participants were exposed to defined acoustic stimuli, alternating with neutral phases lacking acoustic content in a listening room. Concomitant recording of electrocardiogram (ECG) and respiratory rate was performed. Subjective estimation of noise-induced discomfort of assigned vehicle ensembles was rated on a personal ranking scale (PRS) by the study subjects. Subjective ratings were combined with objective psychoacoustic parameters by multiple regression analysis. Results Heart rate was increased during all noise exposure phases compared to neutral phases; the increase of heart rate differed among vehicle ensembles and was statistically significant in two cases ( p<0.01). Respiratory rate remained unaffected. Personal rankings also differed among vehicle ensembles and correlated well with objective psychoacoustic parameters ( p<0.0001); e.g., loudness combined with roughness describes the correlation with subjective estimation of noise-induced discomfort better than the A-weighted sound level. Vehicle ensembles rated more unpleasant caused higher increases in heart rate as well ( p<0.0001). Conclusions The sound quality of road traffic noise as it is described by various psychoacoustic parameters not only determines the subjective estimation of noise-induced discomfort but in addition affects physiological parameters like heart rate. This should be considered for future perspectives in road- and traffic planning and therefore may serve construction engineers as well as traffic planner as a supplemental tool.

BRIDGE LANE DIRECTION SPECIFICATION FOR SUSTAINABLE TRAFFIC MANAGEMENT

We present a deterministic model that specifies lane direction in a multi-laned bridge that has a movable barrier that divides the two directions of traffic flow, in order to reduce congestion. A probabilistic dynamic programming formulation for a stochastic extension of the model is also presented. Analysis of the special structure of the dynamic programming formulation provides new insights into important aspects of certain traffic planning problems and represents a useful addition to the traffic network planner's toolkit. A case study involving the lane direction management of an actual bridge is also provided.

Cordon-based congestion pricing in a continuum traffic equilibrium system

This paper presents an application of the continuum traffic equilibrium model for the cordon-based congestion pricing problem. The traffic equilibrium model treats densely spaced roads as a continuum over which commuters are continuously dispersed. Suppose in the morning peak-hour, all commuters travel to the central business district (CBD) by taking their individual shortest routes. Their user-optimal route choice behavior, with or without toll pricing, can be formulated as a calculus of variations problem and solved efficiently by the modern finite element method. By plotting the numerical results in a two-dimensional space in the form of contour lines of travel cost to the CBD, one can intuitively identify the level of congestion and the external cost anywhere in the city. Hence, the continuum model and two-dimensional numerical representation allow a traffic planner to select easily one or multiple toll cordon(s) in the city and evaluate the impact of cordon toll charges on the resultant social welfare and user benefits.

A first best toll pricing framework for variable demand traffic assignment problems

In this paper, we present a toll pricing framework for a general variable demand traffic assignment problem with side constraints, where the demand between an origin destination pair is a function of the least total travel cost for making the trip. This general demand model unifies earlier toll pricing treatments of the variable demand models including elastic demand traffic assignment problems and combined distribution assignment problems. All of these models have the constant toll revenue property. Given that users experience the side constraints, we show that when they are charged by a toll vector in the first best toll set, the system optimal flows and demands are achieved. We then present a toll pricing framework by which a traffic planner might find the most appropriate toll vector given certain restrictions and objectives on the network. Finally, we derive the toll sets and illustrate the toll pricing framework for specific instances of the general variable demand models.

Trial-and-error implementation of marginal-cost pricing on networks in the absence of demand functions

Conventional analysis of optimal congestion pricing relies on three primary elements, namely, the speed–flow relationship, the demand function, and the generalized cost. Analytical demand functions tailed for congestion pricing are, however, difficult to establish in practice even with advanced transport modeling techniques. Inspired and motivated by the recent commentary and analytical works in the literature, this study proposes a trial-and-error implementation scheme of marginal-cost pricing on a general road network when the demand functions are unknown. Given a trial of a set of link tolls, the revealed aggregate link flows can be observed at ease; based on the observed link flows, a new set of link tolls can be determined and used for the next trial. We propose such an iterative toll adjustment procedure based on the method of successive averages, and present a rigorous theoretical proof of its convergence. The iterative procedure presented here allows for a traffic planner to estimate easily the socially optimal congestion tolls in a network without resorting to demand functions.