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Operators and designers of public transport systems such as railways and buses are becoming increasingly driven by three important issues: the need for reliability of equipment, being environmentally friendly, and ensuring passenger safety, especially in the age of Covid-19 and beyond.

Before addressing reliability, the environment has become one of the number one concerns of today.  In the context of transport networks, consider the recent past when all the doors on a train or bus would be opened at every stop, whether a passenger wanted to board or disembark or not. When you have heating or air-conditioning running to create a pleasant internal environment for passengers, the very act of automatically opening every door at every stop would inevitably mean more energy is used to heat or cool the carriage after every time the doors are opened.

To address this, many modern trains and buses incorporate a stop request button, to limit the door opening to only when a passenger actually needs to board the carriage or exit.

While this goes some small way toward being environmentally friendly, the doors could still open and close up to 300 times a day on a busy route with multiple stops, resulting in wear and tear and hence potential reliability issues.

This repetitive opening and closing can lead to component failure within the door mechanism, and especially lights, mechanical switches and pushbuttons. When such components fail, while the cost may be insignificant in the grand scheme of things, the impact on revenue when the whole compartment is out of action can mount up – especially if the components fail regularly.

And it’s not just external doors that are affected. The switches and pushbuttons are also used on the doors for transiting between carriages, for on-board lavatories, for flushing a toilet or to call for assistance. They are also very much a part of the driver’s cabin on the dashboard, where the pushbuttons are easily prone to breakage or failure, from spilled drinks or careless usage.  In all these situations, the pushbuttons could break or fail due to mechanical wear or vandalism from both passengers and drivers.

Because these pushbutton switches are mechanical components, they are more susceptible to failure.

One way of overcoming the vulnerability of the mechanical pushbutton switches is to use switches without moving parts – in other words, capacitive switches. The CAPTRON SENSORswitches are a good example of this type of capacitive touch switch used to open doors or make stop requests without having to apply any mechanical pressure to the switch.

They are extremely reliable, with the potential to operate hundreds of millions of switching operations without failing, and able to withstand the harshest of conditions to make them 100% water and oil proof, as well as vandal proof.

As an indication of their longevity, CAPTRON capacitive sensor switches were first installed in Munich’s underground railway system in 1994 and are still working reliably and seamlessly today. They are also used in buses in Dubai, in the United Arab Emirates. Traffic and transport reference customers using CAPTRON switches range from Airbus and Bombardier to Deutsche Bahn and the Shanghai Metro.

An example of CAPTRON’s range of capacitive switches for traffic and transport is the CHT4 Series. These have a large touch operating surface area of 63mm and provide visual, tactile and acoustic signals through 16 LEDs, vibration and a beeper. Like all CAPTRON switches, they are extremely shock-resistant, especially since the sensor cannot be destroyed by lighter flames or severe blows. They are completely sealed in cast resin, so don’t suffer from water ingress or the effects of wear and tear.

A case study from the X’Trapolis train produced by Alstom illustrates the reliability of the CAPTRON switches. The previous switches needed to be changed because of vandalism and failing of LEDs. In addition to that, the customer wanted to increase compliance with the Disability Discrimination Act (DDA). They needed a sensor switch including aluminium plate in order to meet the existing design template within the passenger entrance doors of 165 trains, which amounted to replacing 5,904 mechanical pushbuttons.

In a comparison, while the unit cost and installation costs were in the same ballpark, CAPTRON’s SENSORswitches offered a prospective lifetime of 10 years, compared to just 2 years for the competing switches.

In another case study, for the transition doors between compartments in a fleet of 160 Desiro Class 350 trains, the CAPTRON SENSORswitches offer a prospective lifetime of 10 years, compared to just 1 year for competing switches.

These two case studies indicate that the significantly increased lifetimes (and hence operations of the switches) can help reduce downtime and reduce maintenance costs.

A third aspect mentioned at the beginning of this article is the safety element; this is especially relevant with respect to overcome passengers fears of the transmission of Covid-19 by touching switches. Here, since the CAPTRON switches are fully encased, they become easier to clean and disinfect. That’s because there are no gaps as encountered in mechanical pushbuttons, so the switch can remain effective even after being cleaned multiple times.

In summary, capacitive switches such as CAPTRON’s SENSORswitches help train and bus operators to maintain a more
reliable service, by helping reduce the risk of failure of one of the key components in their systems, the pushbuttons used by passengers and drivers hundreds of times a day.

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