Summary 1.Roads provide suitable conditions for the establishment and growth of exotic species. Most roads are bordered by drainage ditches forming a network of linear wetlands. Drainage ditches may serve as habitats and corridors facilitating the spread of aquatic invaders into the intersected ecosystems. The common reed Phragmites australis is one of these aquatic invaders frequently found in marshes and drainage ditches along roads. We hypothesized that highways have acted as corridors for the dispersal of the common reed and have contributed to the invasion of North American wetlands by this species. 2. We mapped the spatial distribution of the common reed along the highway network of the province of Quebec, Canada, where a large-scale invasion of this plant species has been reported since the 1960s. We also identified the genotype of common reed colonies using molecular tools and the main characteristics that favour the presence of the common reed in road ditches.3. Approximately 67% of the 1359 1-km highway sections surveyed during summer 2003 in Quebec had at least one common reed colony. End to end, common reed colonies totalled 324 km, i.e. 24% of the 1359 km surveyed. 4. Common reed colonies located along the highways were largely (99%) dominated by the exotic (Eurasian) genotype (haplotype M). 5. The common reed was more abundant along highways located in warm regions, with a sum of growing degree-days ( > 5 ° C, 12-month period) ≥ 1885, along highways built before the 1970s and in agricultural regions dominated by corn and soybean crops. Common reed colonies were larger when located along highways that were wide, built before the 1970s or in warm regions. This was particularly apparent if the roadside was bordered by a wetland. On the other hand, common reed colonies were more likely to be narrow when located near a woodland. 6. Synthesis and applications. Several disturbances (de-icing salts, ditch digging and agricultural nitrogen input) favour the development of large common reed colonies along roads, some of them expanding out of roadsides, particularly in wetlands. Reducing disturbances, leaving (or planting) a narrow (a few metres) hedge of trees or shrubs along highways or planting salt-resistant shrubs in roadside ditches could be efficient ways to slow the expansion of common reed or to confine the species to roadsides.

Urban work trips have changed in important ways during the last decades. In Qu e ebec City, a medium-sized Canadian metropolitan area, commuting distances increased for both male and female workers between 1977 and 1996, while durations increased for male workers and decreased for female workers. This article seeks to identify spatial and social factors responsible for these changes. We develop a disaggregate model of trip duration estimated on the basis of large samples derived from travel surveys comparable through time. Using categorical variables to specify change, we are able to separate change effects from level effects attributable to various dimensions of urban form. Our analysis clearly indicates that, once travel mode and key social factors are controlled for, the shift from a monocentric to a dispersed city form is responsible, in the Qu e ebec metropolitan area, for increasing commuting time. This is contrary to findings in larger metropolitan areas, where, it has been argued, the suburbanization of jobs maintains stability in commuting duration.

This paper presents a procedure for considering interactions of neighbourhood quality and property specifics within hedonic models of housing price. It handles interactions between geographical factors and the marginal contribution of each property attribute for enhancing values assessment. Making use of simulation procedures, it is combining GIS technology and spatial statistics to define principal components of accessibility and socio‐economic census related to transaction prices of single‐family homes. An application to the housing market of the Quebec Urban Community (more than 3,600 bungalows transacted in 1990 and 1991) illustrates its usefulness for building spatial hedonic models, while controlling for multicollinearity, spatial autocorrelation and heteroskedasticity. Distance‐weighted averages of each property attribute in the neighbourhood and interactions of property attributes with each principal component are used to detect any spatial effect on sale price variations. This first‐stage spatial hedonic model approximates market prices, which are then used in order to compare “expected” and actual property tax amounts, which are added to obtain a second‐stage model incorporating fiscal effects on house values. Interactions between geographical factors and property specifics are computed using formulae avoiding multicollinearity problems, while considering several processes responsible for spatial variability. For each property attribute, they define sub‐models which can be used to map variations, across the city, of its marginal value, assessing the cross‐effect of geographical location (in terms of neighbourhood profiles and accessibility to services) and its own valuation parameters. Moreover, this procedure distinguishes property attributes, exerting a stable contribution to value (constant over the entire region) from those whose implicit price significantly varies over space.

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Background: Identification of socioeconomic and health inequalities at the local scale is facilitated by using relevant small geographical sectors. Although these places are routinely defined according to administrative boundaries on the basis of statistical criteria, it is important to carefully consider the way they are circumscribed as they can create spatial analysis problems and produce misleading information. This article introduces a new approach to defining neighbourhood units which is based on the integration of elements stemming from the socioeconomic situation of the area, its history, and how it is perceived by local key actors.