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Hatch Goba: Bridge City Railway Station Project


Project title:
Bridge City Railway Station Project ensuring optimum levels-of-service through pedestrian simulation incorporating Virtual Reality (VR)

Contracting authority:
Passenger Rail Agency of South Africa

Engineering Consultants: Hatch Goba (Pty) Ltd., Arcus Gibb
Contractors: ENZA Construction & Grinaker - LTA

Public Authority
Project duration: 6 months (2010)

Project description:

This project encompasses the construction of a 3 km rail spur from the existing Duffs Road station to the Bridge City development node in Inanda, 17 km from the Durban City Centre (South Africa). To facilitate the change of modes at Bridge City, an integrated road-to-rail modal interchange has been provided incorporating a new commuter rail station, minibus-taxi rank, commuter bus rank and related commuter convenience, retail and other facilities.

The Intermodal facility will incorporate transport areas on different levels linked by stairs, escalators and lifts. Bridge City will, in the near future, be linked to the existing Metro commuter line splitting into four rail lines at the interlocking serviced at the station by two platforms to cater for the anticipated demand.

Station design modelling approach
Hatch Goba utilised PTV Vissim, the world’s leading state-of-the-art pedestrian simulation software, for the assessment of the Bridge City station. For stations such as Bridge City that provide vital interchanges between several public transport modes, pedestrian simulation and analysis are being employed to provide an additional level of assessment to ensure that the levels-of-service required by the Rail Agency are met.

In this case, pedestrian simulation modelling during the design process was used, not only to test the proposed architectural layout and associated levels-of-service based on static calculations, but also to provide input to the Virtual Reality (VR) model. The effectiveness of the evacuation potential of the station was also tested.

An early version of the station layout that was fully compliant with the manual station sizing requirements was interrogated with pedestrian simulation which provided longitudinal pedestrian density plots of various station infrastructure items such as platforms, staircases (refer to Figure 1), concourses, turnstiles, foyers etc.

The result of this analysis was compared to the acceptability criteria objectives of the Passenger Rail Agency of South Africa (PRASA).

In some aspects, in particular the pedestrian flow rate criteria on staircases from platforms to concourse level, failed to meet the standard prescribed by PRASA, particularly during the PM peak period with the higher alighting loads. The design team responded by recommending that both sets of escalators should run in the ascending direction during this time period only. Any passengers wishing to board during this time have the option of using the stairs or the lifts.

The updated layout was then subjected to an evacuation assessment where improvements to the escape door widths and platforms ramp ends were proposed.
By responding to the key model findings of the analysis of the initial layout, the design team could make changes with sound reasoning. Furthermore, the effectiveness of the design was assessed according to the required level-of-service criteria and the assessment of various scenarios provided the necessary confidence that the optimised design would withstand dynamic load effects whilst providing acceptable levels-of-service for station users.

Incorporation of Virtual Reality (VR)
In response to the clients’ ambition of creating a world class station facility, Hatch Goba, together with Sunovatech India, developed and tested a 3D VR simulation model. Viswalk output data (viz. from the Pedestrian Protocol Data record) is processed using an advanced 3D VR Processor (SVR Bridge v5.1) that links this data with the objects created and designated in 3D Studio-Max which then behaves exactly the same as the pedestrians modelled in Vissim.

This 3D model is then further enhanced by rendering pedestrians and draping infrastructure in standard or high definition resolution obtained from real-life photography.
The VR simulation outputs were not only instrumental in understanding and testing the proposed design, but also provided a key visual tool for designers to explain the proposal to stakeholders and the public. Typical examples of three dimensional VR rendered outputs for the Bridge City railway station compared to the final constructed product, is shown in the figures below.

Software & modules used:
PTV Viswalk

Further information:
Hatch Goba (Pty) Ltd.

Platform 1 to concourse PM peak staircase Longitudinal LOS plot
Escalator movement simulation. The glass structure encapsulating the escalators is not merely an aesthetic addition, but has a specific function to restrict smoke ingress to the upper concourse level should a fire break out at platform level
A view of the ticket sales booths and railing
A view from the Concourse area en-route to the (HSAG) access gates
Platform waiting area
Platform alighting VR simulation
High Speed Access Gate (HSAG) arrangements at the Concourse level