This paper deals with the analysis of hazards associated with accidental release of high pressure from gas-pipeline transportation system. Simplified equations which are related to the fluid properties, operating pressure, the diameter of pipeline, hole or rupture diameter and the length of the pipeline have been used for the hazard analysis due to pipeline failure. The kind of release (i.e. leak) through a hole or the complete rupture was found not to affect the effective release rate because of an increase in the operating pressure. Among various gases, the release rate of butane with lower value of specific heat ratio (gamma) is found to be always higher than that of propane and methane which have higher value of gamma. Decay coefficient, defined as the ratio of release rate at any instant and to the initial maximum release rate, decreases with an increase in the leak (or hole) size. The accident affected distance increases with an increase in the hole size. During the leakage of natural gas and petroleum gas pipeline, affected distance of hazard is slightly higher for fire as compared to other events. The simplified models can be used with confidence to estimate the hazard distance or hazard area. The procedure developed will be helpful for safety management or emergency response planning for the pipeline transportation of the natural gas and petroleum gas. (C) 2016 Elsevier Ltd. All rights reserved.