The Impact Project is a cooperative work between UNICAMP, General Motors do Brazil and Mercedes -Benz do Brazil, whose main goals are to design, construct and test reliable underride guards for trucks, trailers and semitrailers, and to present solutions to government authorities. To attain these aims two underride guards were designed and three crash tests carried out. The results were used as reference to elaborate a new Brazilian standard. This paper highlights the underride question from a technical point of view, reviews the activities already carried out by the Impact Project and discusses the new Brazilian standard regulating underride guards. Copyright © 2000 Society of Automotive Engineers, Inc. Schmutzler, L.O.F., A Trap for Humans: The Challenges of the Guillotine Effect. IV International Mobility Technology Conference & Exhibit (1995) SAE Paper No. 952207, , São Paulo, Brazil, October, 1995. Society of Automotive Engineers, IncSchmutzler, L.O.F., Brazil's heavy vehicle rear underride problem: A technical-judicial- social and political challenge (1997) SAE Heavy Vehicle Underride Protection TOPTEC, , Palm Springs-USA, Apr. 15-16, 1997Tomassoni, J.E., Bell, G.K., An approach to developing underride guard requirements for improved occupant protection (1980) SAE 801422, , Society of Automotive Engineering, IncBeermann, H.J., Behaviour of Passenger Cars on Impact with Underride Guards (1984) Int. 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Society of Automotive Engineers, IncRechnitzer, G., Powell, C., Seyer, K., Development and testing of energy absorbing rear underrun barriers for heavy vehicles (1996) 15th International Technical Conference on the Enhanced Safety of Vehicles, , Melbourne, Australia, May 13-17, 1996Schmutzler, L.O.F., An underride guard design for the Brazilian traffic environment: Working for a solution (1997) SAE Heavy Vehicle Underride Protection TOPTEC, , Palm Springs-USA, Apr. 15-16, 1997Rechnitzer, G., Design principles for underride guards and crash test results (1997) SAE Heavy Vehicle Underride Protection TOPTEC, , Palm Springs-USA, Apr. 15-16, 1997NHTSA (National Highway Traffic Safety Administration) - Office of Crashworthiness Research (OCR) Vehicle Data Base Query Screens, , http//www-nrd.nhtsa.dot.gov/include/nrd10/nrd11/ocrquery.htmlMariolani, J.R.L., Arruda, A.C.F., Santos, P.S.P., Mazarin, J.C., Stellute, J.C., Design and test of an articulated rear guard able to prevent car underride. VI International Mobility Technology Conference and Exhibit (1997) SAE Paper 973106, , Oct. 27-29, 1997, São Paulo, Brazil. Society of Automotive Engineers, IncRegulation No. 58 - Uniform provisions concerning approval of goods vehicles, trailers and semi-trailers with regard to their rear underrun protection (1983) Economic Commission for Europe of the United Nations, , E. C. E. -. July 11, 1983Resolução No. 805/95 - Estabelece os requisitos técnicos minimos do párachoque traseiro dos veículos de carga (1995) Conselho Nacional de Trânsito, , CONTRAN -. October 24, 1995FMVSS No. 223 - Rear impact guards (1997) National Highway Traffic Safety Administration, , NHTSA -. October 1, 1997 (rev.)FMVSS No. 224 - Rear impact protection (1997) National Highway Traffic Safety Administration, , NHTSA -. October 1, 1997 (rev.)Arruda, A.C.F., Schmutzler, L.O.F., O Projeto Impacto (1997) Anais Do IX Simpósio de Engenharia Automotiva, pp. 440-445. , AEA, São Paulo, Brazil, August 26-28, 1997. págMariolani, J.R.L., Schmutzler, L.O.F., Arruda, A.C.F., Occhipinti, S., Santos, P.S.P., Mazarin, J.C., Stellute, J.C., First Crash Test of the New Conceptual Pliers Underride Guard. VII International Mobility Technology Conference & Exhibit (1998) SAE Paper 982879, , São Paulo, Brazil, November 9 to 11, 1998. Society of Automotive Engineers, IncMariolani, J.R.L., Schmutzler, L.O.F., Arruda, A.C.F., Occhipinti, S., Santos, P.S.P., Mazarin, J.C., Stellute, J.C., Resolução CONTRAN No. 805/95 não garante segurança aos ocupantes de automóveis (1998) Simpósio Tendências Tecnológicas Automotivas, , Associação Brasileira de Engenharia Automotiva (AEA), São Paulo, October 18, 1998Mariolani, J.R.L., Schmutzler, L.O.F., Arruda, A.C.F., Occhipinti, S., Santos, P.S.P., Mazarin, J.C., Stellute, J.C., Impact Project: Searching for Solution to the Underride Problem. International Truck & Bus Meeting & Exposition (1998) SAE Paper 982755. (Published Also In: Truck and Bus Safety Issues, SP-1400 and in Transactions of SAE: Journal of Commercial Vehicles 1998), , Indianapolis, USA, November 16-18, 1998. Society of Automotive Engineers, IncBloch, B., Schmutzler, L.O.F., Improved Crashworthy Designs for Truck Underride Guards (1998) Proceedings of the 16th International Technical Conference on the Enhanced Safety of Vehicles, 2, pp. 933-845. , Windsor, Canada, May 31 to June 4, 1998Schmutzler, L.O.F., Pára-choque para Caminhões: A Experiência do Projeto Impacto da Unicamp (1998) Simpósio Tendências Tecnológicas Automotivas, , Associação Brasileira de Engenharia Automotiva (AEA), São Paulo, Brazil, August 18, 1998Mariolani, J.R.L., Santos, P.S.P., Arruda, A.C.F., Projeto de Para-choque Traseiro de Caminhão com Auxílio do Método dos Elementos Finitos (1997) Anais Do IX Simpósio de Engenharia Automotiva, pp. 452-459. , AEA, São Paulo, Brazil, August 26-28, 1997. pág(2000) 2°. Projeto de Norma 39:002.01002:1999 - Pára-choque Traseiro Para Caminhõese Veículos Rebocados Com Mássa Total Maxima Acima de 4,6 T - Requisitos e Método de Ensaio, , A. B. N. T. -. Associação Brasileira de Normas Técnicas, Rio de Janeiro, Brazil, April 2000