Design for horizontal escape in buildings: The use of the relative distance between exits as an alternative approach to the maximum travel distance

In the UK, Fire Safety Strategies (FSS) for buildings have been adopting fire engineering solutions to address complex issues. These issues are commonly related to fire, such as: positioning and dimensioning of smoke vent extractors, atria dimensions, etc. Nevertheless, in terms of means of escape, the FSS appear to be attached to a more prescriptive approach. In reality, the principal building regulations document for fire safety in the UK, well known as Approved Document B (AD B), is essentially prescriptive in nature. And this is the main source of information when defining the exits locations; which takes the maximum travel distance as the key-factor to establish the escape routes. Probably, for this reason, in many real cases, the building regulators seem to be reluctant to alternative solutions when come to define the exits locations. In the other hand, the British Standards, such as BS 7974, already present methodologies to enable fire engineering solutions. Nevertheless, the exits locations are not covered. Therefore, this paper presents an alternative approach to the maximum travel distance when defining the exits locations. This approach is based on the use of the relative distance between exits (RDBE). The author has shown previously that the relative distance between exits do impact the evacuation efficiency, especially in high dense populated environments. In this paper, a case study based on the AD B is analysed through evacuation modelling. The results have shown that the exits locations, when defined by the RDBE, can provide safe means of escape.