SUMMARY OF THE THESIS
The occupational accidents rate nowadays constitutes a problem of first order in all the aspects, as much in the economic scope as social in Spain, where the indices of risk in the construction sector are over the European average. Within this general frame, the aim of this thesis is to define a methodology for the quantification of the labor risks that allows, if used properly by the involved agents, the reduction of the occupational accidents in the construction.
This project has been developed in three main stages: the first one studies the state of the knowledge and the evolutionary tendencies in research based on labor risks; the second stage involves a statistical analysis of the occupational accidents in Spain and its specific application to the construction sector; and the last one proposes a model to estimate and calculate the costs involved  in the occupational accidents of a construction site with the purpose to establish the fundamental variables that will make operational the model developed in this research. 
For the analysis of the current state of the knowledge it has been defined a process or cycle compounded by different successive steps over the time that reflects the reality of the occupational safety and health in the construction industry; this process is entitled cycle risk-accident and consists of five steps: regulation, education, risks assessment, risks prevention, and accidents analysis.
The statistic analysis of the occupational accidents was maded using current statistical series provided by the “Ministerio de Trabajo y Asuntos Sociales” and with open relevant information that allowed us to establish comparisons by autonomous community, economic sector, according to gravity, type of accident, form in which they are produced, etc.
For the accomplishment of the theoretical exposition of the costs that take part in the occupational accidents of a construction site and to establish the methodology of estimation and calculation, three blocks were used to group the costs: securing, prevention, and accidents; and a fourth block was established that although is not a cost, allows the employer to know the amount of money to recover from the social security in case of an accident.
Based on the previous statements, finally, it has been considered, designed, and developed a model of quantification of labor risks in the construction sector, with support on information systems. This model is able to offer enough information so the management can make the most advisable decision for its own company based on the budget of the construction site, on the investment in prevention of labor risks for each construction site before its beginning.