The world's first heavy metro platform screen door system was successfully installed in Singapore on the Singapore Mass Rapid Transit (SMRS) in 1987 but now, some 22 years later, the concept is still far from being a common feature on rail platforms worldwide. In fact, it has taken only relatively tentative steps forward, except in China where it has poignantly become mandatory at all rail stations.
This lack of widespread deployment is perplexing considering the enhanced safety platform screen doors offer passengers, alongside the benefit of keeping platforms quieter and cleaner. While evidence of an increased adoption of the concept is found on automated internal airport rail links and on some newer modern rail networks, traditional structures, particularly in Europe, generally remain untouched.
As the company behind that first installation in 1986, Westinghouse Platform Screen Doors (WSPD) has been a major player in the history of this niche market. According to the UK-based company's business development manager Colin Fullalove, the technology of the doors has evolved significantly since its introduction:
"The first system we built used basic technology that operated pneumatically with the doors," says Fullalove. "Since then the operating equipment and control systems have gone through a number of stages of evolution in order to get to today's fully software-configured systems."
"Originally WSPD operated on a project-by-project basis, whereby the business and products were tailored to each customer's requirements. Every project became a learning curve for the company until we standardised the processes and the business ultimately became more of a standardised product. We now manage 15–20 projects concurrently and have a catalogue of bespoke solutions."
Sliding doors and Chinese laws
Following the Singapore installation, WSPD was involved with a number of key projects in Asia, including stations in Kuala Lumpur and Hong Kong. In Europe, the company was in particular responsible for the 476 sliding doors fitted on London Underground's Jubilee line, completed in 1999.
The real market turning point for WSPD, however, occurred in 2002 when the company was involved with the first platform screen door system in China on Guangzhou's Metro Line 2.
The significance of the project was not simply down to its size – which included fitting a total of 1,020 doorways on 34 underground platforms. It was also hugely significant because its success led to the system becoming a mandatory requirement in China.
"There has been an explosion of market demand for platform screen doors in China since 2002," Fullalove says. "In fact, there has been as much demand in China as there has been from the rest of the world in total. A main driver behind this is passenger safety. The doors offer a physical segregation between the track and the platform area, so effectively prevent unauthorised access of people or objects entering rail infrastructure."
Certain governments, such as those in South Korea and Japan, have also identified the gates as a method of reducing suicide rates. Whether this is the case, the concept has proven successful at reducing fatalities. This is most notable on Hong Kong's Mass Transit Railway, which reportedly experienced no fatalities on its network throughout the whole of 2006 following the implementation of platform doors.
On some networks, however, platform doors offer hidden value with controlling air-conditioning flow and general ventilation. As well as being able to create a climate-conditioned platform for greater passenger comfort, the screen doors can prevent loss of air-conditioning and ultimately reduce energy consumption.
Given the vast array of platform sizes and constrictions, screen doors are not just a one-size-fits-all solution. WPSD offers three varieties of doors for rail platforms. "All three types of door have proved to be popular with the rail sector," Fullalove says. "During the implementation process, the doors or gates must interface with a number of different elements of the platform. Structurally, the solutions must integrate with the surrounding architecture of the station. They also must physically interface with the size and positioning of the train doors. Additionally, the doors must be configured to interface with the platform's controls system, including the signalling and monitoring."
The company's most mature product is the full-height platform screen doors – typically about 2.1m high – which are structurally attached to the platform and its ceiling. This provides a full-height barrier which contains tunnel ventilation and platform cooling.
Platform edge doors – as found on London Underground's Jubilee line – are similar in appearance, but are structurally counter-levered off the platform. This means the doors leave a gap between their top and the ceiling, allowing free airflow to run between tunnels and platform. WSPD's most recent introduction is platform safety gates, which provides a half-height barrier that particularly compliments platforms with limited space. The company has recently won a contract for retrofitting approximately 2,000 safety gates for an above-ground network in Singapore.
A typical installation period can run from one to six years depending on the size and complexity of each station – retrofitting doors to an existing platform takes less time than a new build situation. Given the history and positioning of some railway platforms, feasibility studies are required to see if compatibility is possible.
A large factor in the adoption of platform screen doors in China, for example, lies with the compatibility of its relatively new rail infrastructure and WSPD's designs. "China has a very standard system – the platforms are about 130m long with roughly 24 doors per train. The platforms are straight and because the lines are new, there is dedicated rolling stock on each line so you have none of the complexities of mixed rolling stock," Fullalove says.
Yet in Europe, the lack of platform doors visible on existing rail infrastructure proves retrofitting is possibly not as good a solution as it is in China. In London for example, there are currently no plans in place to extend platform screen doors to the majority of the other underground networks.
Fullalove, however, says he believes this market is beginning to change. "There are major cities in Europe that are considering retrofitting, and for example, we have had interest in Madrid towards our products," he explains.
"We are now able to offer systems that are more price-competitive then when we first installed the Jubilee Line.
"The knowledge and experience we have gained from past projects has allowed us to develop our processes and therefore turn around much larger systems in much shorter time periods. In 2007, we installed a system twice the size of the Jubilee Line in Shanghai but took only a third of the time to do it."
With China becoming a successful working example of the benefits of platform screen doors, perhaps it will not take long for rail infrastructure in Europe to completely follow suit.