Situations in traffic - how quickly they change

Spatio-temporal correlations of intensity of traffic are analysed for one week data collected in the motorway M-30 around Madrid in January 2009. We found that the lifetime of these correlations is the shortest in the evening, between 6 and 8 p.m. This lifetime is a new indicator how much attention of drivers is demanded in given traffic conditions.Comment: 9 pages, 6 figure

Economic impacts of high labour cost and herbicide resistance for the management of annual barnyardgrass (Echinochloa crus-galli) in rice production in the Philippines

Implications of increasing labour cost and development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It may be worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.Barnyardgrass, Bioeconomic model, Herbicide resistance, Integrated weed management, Rice production, Crop Production/Industries, Farm Management, Research and Development/Tech Change/Emerging Technologies,

RIMPhil: a bioeconomic model for integrated weed management of annual barnyardgrass (Echinochloa crus-galli) in Philippine rice farming systems

This paper describes a complex, dynamic simulation model that has been developed for the analysis of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice farming systems in the Philippines. Users of the model may simulate any feasible combination of 49 weed treatments options across wet and dry cropping seasons over 5, 10, 15, and 20 year periods, subject to a predetermined sequence of planting methods. The main outputs of the model include weed seed and plant densities and seasonal and annualised profit over the simulated planning horizon. Model output emphasises the substantial economic benefits associated with effective long-term weed management strategies. In addition, the most-profitable weed densities are found to be much lower than those usually recommended to producers, indicating the importance of considering economic factors in the formulation of management recommendations. Results broadly indicate that a mixture of chemical and non-chemical treatments provides good weed control in rice crops, and maximises long-term profit for systems where the main weed is annual barnyardgrass. However, the performance of this strategy is influenced by crop establishment method and weed density level. These indicative results emphasise the value of the model for guiding the efficient control of annual barnyardgrass in rice crops in the Philippines.Barnyardgrass, Bioeconomic model, Integrated weed management, Rice farming systems., Agricultural and Food Policy, Crop Production/Industries, Environmental Economics and Policy, Farm Management,

Solving the p -Median Problem with a Semi-Lagrangian Relaxation

Lagrangian relaxation is commonly used in combinatorial optimization to generate lower bounds for a minimization problem. We study a modified Lagrangian relaxation which generates an optimal integer solution. We call it semi-Lagrangian relaxation and illustrate its practical value by solving large-scale instances of the p-median proble

Factors that affect the use of herbicides in Philippine rice farming systems

This study involves the application of a random-effects double-hurdle model to survey data to identify the farm-level factors affecting the adoption and intensity of herbicide use in rice production in the Philippines. Results broadly indicate apparent differences in the degree to which important explanatory variables affect the intensity and adoption decisions. The age of the farmer, household size, and irrigation are the significant predictors influencing the decision of farmers to use herbicides, while economic variables such as the price of herbicides, total income of farmers, and the use of bank loans or credit are the highly significant factors determining the intensity of herbicide use. Significant determinants of both the adoption and intensity decisions are land ownership, farm area, and the method of crop establishment used. Results suggest that all of the identified significant predictors in both herbicide use decisions can be considered by the national government when designing policies to reduce excessive use of herbicides or to encourage the adoption of alternative methods of weed control. This is important because for small rice producers, like the majority of Filipino farmers, improved weed management techniques that build on their traditional practices and that are compatible with their resources will be more easily adopted by farmers, relative to those that require radical change to the entire farming system.Herbicide use, Double-hurdle model, Adoption, Rice farming system., Demand and Price Analysis,