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Working out a relationship between the spatial approach and the network approach to the study of road systems has become all the more urgent today, since it has become the responsibility of the road system to provide the linkage between urban areas and the mobility of those live there, between the global and the local. This article connects the urban road system with three properties, which participate in the nature of this area-network and determine certain consequences of urban planning as well. They are accessibility, mutability and imageability, and they make it possible to assess the aptitude of planning to participate in organizing urban areas, namely in maintaining the balance of supply of short- and long-distance travel, contributing to the perception and representation of territory, and integrating action connected with the road system into long-term strategies. Evaluating the quality of the service of the road system in terms of shape, or configuration, introduces here the notion of road density, which follows from a postulate that urban density, interpreted as the intensity of use of urban space, depends as much upon the density of roads as upon the density of built-up spaces. The notion of road density makes it possible to evaluate the spatial relationships between road system, urban space and buildings. The multiple capacities of the road system to organize urban space itself should bring about in the first place a preoccupation with this area-network. Paradoxically, this is the condition for providing alternatives for everyone, especially local authorities, to arbitrate between the global and the local, between time and territory according to which mode of travel is given priority. It is with respect to this alternative that the relationship between a spatial approach and a network approach to the urban road system appears today to be particularly operational.

On the ground that they unavoidably mix car drivers and residents, many contemporary urban planners consider that distributor and collector roads should not exist: to them, apart from expressways, an ideal street network should be made up of only residential streets and boulevards devoid of dwellings. This model is based on the assumption that traffic is not compatible with the day-today life of street dwellers. To the opinion of most planners, only dead-end streets are suitable for residential areas. This article suggests, however, that traffic externalities are not always negative. The case of Bangkok's dead-end streets opening to traffic shows that street dwellers may be satisfied with a higher-than-negligible traffic volume. This is related to the fact that more traffic generally means better accessibility and more opportunities for commerce. Even if one should be cautious in inferring general rules from particular cases, one may at least conclude that the appearance of distributor roads in the urban fabric is not necessarily pathological. The differentiation of streets must be understood as a consequence of the fact that territorial and local uses of the urban space are maintained together in a complex relationship, constituted by a dynamic mixture of repelling and attractive forces. These findings may seem of little account but, considering how urban planners work in general, they deserve to be repeated again with a certain degree of insistence.

In the area of traffic safety, reducing urban traffic speed is an important question. Does street "morphology" influence drivers enough to cause a significant reduction of speed within the urban milieu? Based upon different behavioral theories and models, the present article analyses these influences and their implications. For this purpose, several Parisian districts {arrondissements) were selected and divided into basic street sections taken to be "morphologicaly homogeneous". Each section was then classified, through a significant number of morphological variables on the one hand, and theough average traffic speed on the other (the speed was calculated by identifying moving vehicles from aerial photographs taken at six second intervals). The "Correspondence Analysis" method was then applied to the street section sample, which appeared to be very structured. We have interpreted this structure as a series of statistical links between traffic speed and several of the above-mentionned morphological variables.

Transporting merchandise within cities is an increasing cause of disturbances and urban pollution. In order to deal with the problem, municipalities have employed a variety of measures over the past few years which range from the traditional (police orders forbidding heavy truck traffic) to the innovative (creation of municipal logistic platforms). In a rapidly evolving local context, this study presents the main elements concerning transportation of freight merchandise in cities. We have carried out a synthesis of the most recent works published on flow and the characteristics of urban freight transport. An analysis of urban public policy concerning freight is presented, which insists on the one hand on the spatial fragmentation resulting from the current organization of traffic regulation authority, and on the other on the development of service-provider policies which will directly offer public services linked to the transportation of freight within cities. A brief development then presents the reform of the "plans de déplacements urbains" (PDU = urban transport planning) which resulted from the French clean air act of December 1 996 and which is beginning to modify local policies concerning merchandise.