STEPS software

STEPS software predicts pedestrian movement under both normal and emergency conditionsSuccessful buildings – including office blocks, sports stadia, shopping malls and underground stations – require people to be able to move freely under normal conditions and evacuate rapidly in an emergency. Using simulation to optimise people flow can result in a more agreeable environment and more effective fire safety design in large and busy locations.

STEPS is a microsimulation tool designed by Mott MacDonald for the prediction of pedestrian movement under both normal and emergency conditions. It originates from the extensive experience of Mott MacDonald in the design of transportation systems, in particular underground rail stations and interchanges, combined with its long experience in developing computer simulation tools for engineering design.

A screenshot from the STEPS softwareBy producing real-time 3D simulations in an easily understandable graphical form, results can be interpreted by both non-specialists and experts alike – helping to identify natural bottlenecks and preferred exits, as well as testing evacuation routes and timings for different emergency scenarios.

Key features

Some key features of the STEPS software can be summarised as follows:

• modern agent-based microsimulation approach
• applicable to both normal and emergency operations
• extensive track record
• efficient handling of large and complex models
• direct import of 2D and 3D CAD models
• 3D interactive (virtual reality) graphical user interface
• route system as alternative to cumbersome origin-destination matrix
• moving vehicles eg trains and lifts
• variety of pedestrian movement metrics with graphical representation

Track record

STEPS has been applied worldwide both by Mott MacDonald and other major engineering consultancies to a variety of major projects and is one of the most widely used pedestrian modelling packages for metro and underground rail systems. Some typical example projects are listed below.

• London Heathrow Terminal 5: station and track transit system
• Minneapolis Light Rail Transit, USA
• Rotterdam Metro, The Netherlands
• Delhi metro, India
• KCRC Shatin-Central Link, Hong Kong
• Luton Network Rail station, UK
• International Centre for Life, Newcastle, UK

A study commissioned by the Railway Safety and Standards Board (RSSB) and completed during 2004 included an assessment of the suitability for station design of seven commercial products. STEPS was judged to be “fully compliant” in four out of the six categories considered – higher than any other product. The full report: Managing large events and perturbations at stations – passenger flow modelling technical review, can be obtained from the RSSB website: www.rssb.co.uk

General principles

STEPS employs a modern agent-based approach which predicts the movement of discrete individuals (virtual people) through three-dimensional space. This is in contrast to the older generation of pedestrian models which treat the problem as one of a continuum flow. The major advantages of agent-based models are that they give a more realistic representation of pedestrian movement and allow the elucidation of subtle but important details of pedestrian movement, thereby giving much greater insight to the designer.

STEPS is one of the most widely used pedestrian modelling packages for metro and underground rail systemsThe approach uses principles borrowed from the theory of cellular automata which are now well-established in the modelling of pedestrian dynamics. Pedestrian crowds, like many self-organising systems made up of individual entities, display complex emergent modes of behaviour which arise from simple deterministic and non-deterministic principles followed by the individuals making up the population. The STEPS model is able to recreate this type of emergent crowd behaviour which is fundamental to effective pedestrian simulation. The modelling approach has been verified and validated by comparison with analytical solutions, internationally-accepted design codes and full-scale testing.

Normal and evacuation modes

The two key modes of operation for STEPS are:

• normal mode
• evacuation mode

with normal mode being the more general. In evacuation mode the STEPS entities are instructed to make their way to the nearest available exit of which they are aware, with their movement modified according to their own individual behaviour characteristics. In normal mode the entities will follow a variety of paths through the model in order to fulfil their different aims (for example: enter the station, buy a ticket and go to the assigned platform).

STEPS predicts the movement of discrete individuals (virtual people) through three-dimensional spaceIn evacuation mode, STEPS can be used to calculate evacuation times, exit usage and other criteria essential for fire-engineering design while in normal mode other parameters may be of interest such as level of service and space usage. Normal mode can be used to examine routine operating conditions, for example morning and evening peak flows, but also to assess operational incidents such as escalator failure or variations in train headway which may cause crowding and other problems.

Model output

There are several types of output available in STEPS (before, during and after a simulation) allowing maximum benefit to be gained from the model.

Interactive 3D visualisation (“virtual reality”)

This is available when building the model and running the simulation. It is possible to navigate through the 3D model in an intuitive manner and observe the movement of people from different viewpoints which can be used to make fly-through animations of the model. Several rendering modes are available such as wireframe or solid and both texture mapping and lighting can be used. If desired, an existing 3D Studio Max model can be imported into STEPS to increase the realism of the visualisation.

Interactive 2D visualisation

This allows detailed information on particular planes, or parts of planes, to be plotted using colour contours. This information includes local densities and usage levels. These contours plots can be animated to show the development of the relevant quantity with time.

Animations and still images

It is possible to record animated sequences either from fixed or moving viewpoints in AVI format as well as still images in JPG, TIFF, PNG and BMP format.

Data export

A wide variety of numerical data can be exported, as selected by the user, such as number of people or density in a specific region and exit usage. The data are written to a CSV text file which can then be imported into a spreadsheet package for further analysis.