Swedish research project studies underground evacuations

Data on current evacuation simulations that involve climbing stairways are outdated and imprecise. A new project being conducted by Lund University seeks to correct this problem by providing better evacuation solutions for underground constructions. 

Buildings are on their way underground, so to speak, and new constructions are now deeper than ever. In Copenhagen, for example, construction of the underground metro system is underway. This trend is also apparent in Sweden, where the next stage of Stockholm’s metro will reach depths of up to 100 metres.

These deep constructions will result in escape routes that include long stairways in the event of an evacuation, and this is something Sweden’s Lund University is currently studying quite closely. The research project, whose title is ‘Ascending Stair Evacuation’, examines how people behave while following escape routes that involve stairs.

– Our ambition is to study how long stairways affect walking speed, as well as which physiological factors come into play, explains Karl Fridolf, a Ph.D. candidate in Lund University’s Department of Fire Safety Engineering and leader of the project.

Existing data is imprecise
The project began in 2013, and the original idea came from an actual need among engineers working with underground constructions such as cellars or metro systems.

– I spoke with a group of engineers who had worked on a large underground project in Stockholm. They had plenty of doubts as to how they should model the construction in relation to emergency exits and escape routes, as they couldn’t find data on how people behave when climbing long stairways during an evacuation, Fridolf recounts.

When he looked into the scientific literature in the area, it became apparent that the existing data had been produced some 40-50 years ago.

– We’ve actually changed physiologically since then. We’ve become older, and there are more overweight people today. At the same time, the data we found involved relatively short stairways that can’t be compared to today’s constructions with longer stairways. All things considered, the data didn’t apply to today’s conditions, he explains.

A 30-storey walk
To find data that better meets today’s needs, the project team is conducting three trials that share a common recipe: a demographically representative group of about 70 test subjects are being asked to climb three sets of stairs, from bottom to top, while having their time, pulse and metabolism rates measured.

The first of the three trials was conducted in a 12-storey building, while the next trial will be held in a 30-storey building to determine whether there is a limit for how long a stairway can be before one should consider alternate evacuation options, such as fire-proof elevators. The data from the first trial has not yet been fully analysed, so it is still too soon to report any final conclusions.

– It does appear, though, that people make it to the top regardless of whether they’re in a hurry or taking their time. Eventually, everyone finds their own tempo, Fridolf says.

Based on the findings of the trials, the project group will obtain precise data about walking speed that can be used in evacuation simulations – and not just for people as a whole, but for separate subgroups, too.

– Because we also have the test subjects’ demographic data, we’re able to assign a specific walking speed to certain groups of people – such as the elderly or those who are overweight – and these speeds can be used to create even more precise simulations, explains Fridolf.

Proper solutions
Today’s evacuation simulations that involve climbing stairs use a single walking speed for all people. Using the project’s data, however, future simulations will paint a much clearer and precise picture of real life evacuation situations. Furthermore, this new type of data will come to influence which solutions are used in future constructions.

– Previously, when engineers performed simulations in a tunnel, they reduced walking speed for safety’s sake if there was smoke in the tunnel. When we studied the matter in connection with the Metro project, though, it turned out that people actually reduced their speed due to the smoke – but not as much as one might expect when coming up with an evacuation model. This suggests that less costly evacuation solutions can be found, Fridolf explains.

This finding may also be the result of the Ascending Stair Evacuation project. With new, precise data, engineers can better calculate exactly which evacuation solutions are needed, instead of using over- or under-dimensioned solutions.

Ascending Stair Evacuation (ASE)
The ASE project began in 2013 and is scheduled for completion in 2015. The purpose is to determine walking speeds for people climbing stairs in evacuation situations, and the information will be used to create more precise simulations. The Department of Fire Safety Engineering at Lund University is directing the project, which is also supported by the Swedish Transport Agency and Brandforsk, the Swedish Fire Research Board. The project has a working budget of approximately €215,000.

The Metro project
Metro was a joint project whose goal was to secure underground railways and tunnels in Sweden. The project was completed in 2012, and the Department of Fire Safety Engineering at Lund University was involved in the evacuation phase. The research teams examined which warning systems had the best effect in a tunnel, and how quickly people moved – though only until they reached a stairway. The ASE project is thus a natural successor to the Metro project, the purpose of ASE is to study what happens when people have to climb stairs during an evacuation procedure. The Metro project had a total budget of around €1.5 million.