In case you missed it, a revealing study was conducted on SanFlickr Creative Commons/miggslives
Francisco’s BART (Bay Area Rapid Transit) system that tested the cleanliness of the seats on a BART rail car.  There have been complaints in the past about a cleanliness problem.  Some passengers take measures of standing up on the train just to avoid coming into contact with the seat cushion material.

The Bay Citizen commissioned Darleen Franklin, a supervisor at San Francisco State University’s biology lab, to analyze the bacterial content of a random BART seat.

Fecal and skin-borne bacteria resistant to antibiotics were found in a seat on a train headed from Daly City to Dublin/Pleasanton. Further testing on the skin-borne bacteria showed characteristics of methicillin-resistant staphylococcus aureus, or MRSA, the drug-resistant bacterium that causes potentially lethal infections, although Franklin cautioned that the MRSA findings were preliminary.

High concentrations of at least nine bacteria strains and several types of mold were found on the seat. Even after Franklin cleaned the cushion with an alcohol wipe, potentially harmful bacteria were found growing in the fabric.

Source: The Bay Citizen (http://s.tt/129fS)

It’s Not Your Customer’s Fault

Can you say “Yuck!”  Apparently replacement cars are on the horizon.  It sounds like BART is considering a plastic-type seat and sacrificing comfort.  Why does the customer always get the hit when it comes to riding public transportation?  It even went as far as asking riders to use hand sanitizers….making it their problem:

“… encouraged riders to wash their hands and use hand sanitizers available at BART stations.”

Hygiene has emerged as a key issue as BART officials determine what kind of seats to install for a new fleet of cars in 2017. In January, system employees were invited to test a variety of seat models at a Hayward warehouse. One employee, Melissa Jordan, filed a report on BART’s website about the trade-offs in selecting the new seats.

“Can I live with some type of seat that’s less cushiony — maybe padded vinyl instead of fabric — if it’s easier to keep clean?” Jordan wrote.

Source: The Bay Citizen (http://s.tt/129fS)

Alternative Seating For Comfort and Clean

The reality is, there are alternatives to seat materials that allow for both comfort AND cleanliness.  Rogers develops materials and seat cushions that do exactly that.

One of the issues facing the current BART seats is the polyurethane foam material under the upholstery.  While it is true that the upholstery itself should be of a bacteria-resistant non-woven material, the foam beneath must also not be a breeding ground for bacteria.  One solution to preventing bacteria growth is to build  cushions from open cell silicone foams!  There is a standard known as ASTM G 21:  Resistance of Synthetic Polymers to Fungi.  The test measures the growth of specific bacteria specimens and organism mixtures.  For those familiar with such bacteria, the ones observed are ATCC 9642, 11797, 6205, 9645, and 15233, with technical names such as aspergillus niger, penicillium funiculosum, and others.  The test uses a rating system from:

  • 0-4 where 0 is no trace
  • 1 is trace (<10%)
  • 2 is light (10-30%)
  • 3 is medium (30-60%)
  • 4 is  heavy (>60%).

Silicone foams for seating cushions receive ratings of either 0 or 1.  The problem with polyurethane materials filled with flame retardant agents (required for subway system passenger seating cushions) is that the fillers compromise the foam causing it to crumble over time and have large porous voids, which becomes a cesspool for bacteria and all kinds of spills.

The new BART specification for future builds already specifies silicone foam for all seats – however, why should the ridership have to to wait for the funding for those new build cars – when the seats could be changed out TODAY with refurbishments and replacements that use the silicone foam.

Besides resistance to bacteria growth, the silicone material is also resistant to fire spread and adheres to the smoke, and toxicity requirements of for subway passenger seating.

Finally, there is comfort.  A silicone foam will not deteriorate or change in its comfort-performing capabilities for a minimum of ten years!

Now BART has an answer to its problem.

Related Links about Rogers Silicone:

Video on Rail Car Seating 101: http://blog.rogerscorp.com/2011/03/04/rail-car-seating-101-silicone-vs-polyurethane/
Silicone Articles:  http://www.rogerscorp.com/hpf/bisco/articles.aspx
Silicone Materials: http://www.rogerscorp.com/hpf/bisco/producttype/4/Bun-Silicones.aspx

Creative Commons Image source: http://www.flickr.com/photos/miggslives/4782378772/

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Ken Kozicki from BISCO® Silicones recently authored an article for Railway Technology International about the design considerations that go into creating comfortable railcar seat cushions.  How important are first impressions for seating when a passenger steps into the railcar? Obviously, if it’s the Orient Express or another high end rail system, the feeling of luxury must be present.  But even for standard commuter railcars, seat cushions do make an impression.  Ken notes:

“…the most prevalent and obvious fixture within any interior, rendering, brochure, or maze of booth exhibits is the seat or array of seats. The type of seat will vary from the most outrageously luxurious – slated for a VIP very high speed Oriental Express pod – to the simplest and ergonomic that allows for rows and rows of passengers in a configuration that would be suitable for the rush hour of London, Shanghai or San Paulo….What has taken teams of engineers and designers months, if not years, to conceptualise, design, prototype, test (and re-test), will be given a judgment in less than ten seconds. So from that, one could wonder just how important is the first impression of a railcar seat?”

In this article, Ken look at the design considerations that need to be factored in when choosing the right seat cushion for a railcar:  Ken highlights the following:

  • the number of seating positions per coach (as required by the transit authority)
  • materials’ standards for flame, smoke, and toxicity (FST)
  • type of train service (urban metro system versus suburban commuter), and
  • severity of usage.

Ken also discusses the new concerns of sustainability and end-of-life:

“This is being driven by questions related to the disposal of the seat: “What will become of a worn, damaged, or obsolete seat?” Will it be thrown into a land-fill? What are the decomposition ramifications of that seat in a land-fill?”

All good questions.  But what about the seat itself and the cushioning material? Are some better than others?  Ken suggests yes, there are differences between one cushioning material from another:

“…cushions have differences in profile, appearance and texture, it is not obvious that there are different types of materials used to fabricate the cushions. These materials are usually in the form of foam, such as a filled-polyurethane, silicone, and melamine. The foam which is specified for the fabrication of the cushion will have been tested to the various FST standards, ensuring the safety of the passengers. In addition, some of the foam materials may have been cycletested to simulate wear and usage, which brings us back to our earlier statement of first impressions. Often, seat cushion foam materials are tested and certified to a characteristic known as indention force deflection (IFD).”

2-D & 3-D view of thin profile seat with loaded urethane

“A typical IFD test method will be comprised of a disk of a determined diameter that compresses the foam material a certain percentage of its thickness, and then measures the amount of “pushback” force the foam has. This is its indention force deflection, and is directly related to the comfort of the seat. In production, the foam will be certified according to this test. If it is within the IFD tolerance range, the foam will be qualified for seat cushion fabrication.”

Of course, Ken highlights that the bigger test happens after many months of wear on the cushion, after the “pushback” force has been worn down.  Different materials, like silicone foam, do a better job over the life of a cushion than other materials.

To read Ken’s final recommendations, either view the article here (in a magazine viewer) or download a full PDF of the printed article.

Related Links

BISCO Material Selection Guide

Floating Floor Design Tool