The process of flame acceleration inside the tubes and channels depends on several parameters such as nature of the fuel involved, composition of the mixture and configuration of the enclosure itself. The wall roughness and the presence of obstacles in the flame path act as a turbulence generator causing continuous flame acceleration. In some situations the flame can reach a sufficiently high speed to allow the transition of the deflagration into a detonation. A considerably large amount of experimental data on flame speed and DDT run-up distance for several mixtures have been accumulated. Nevertheless simple relationships, based on the most relevant parameters governing the phenomenon, could be useful for design purpose and safety assessment. The present paper suggests some simplified formulas for the evaluation of flame speed and DDT run-up distance of flammable mixtures for both smooth and obstacles filled tubes. (C) 2008 Elsevier Ltd. All rights reserved.