Pollen and Trains

The BBC has reported on the problems Arriva Trains have been experiencing with pollen clogging up the radiators on their units:

First it was leaves on the line, then the wrong kind of snow, now pollen has caused problems for rail managers.

High levels of it over the summer blocked some train radiators on the Cambrian Line between Shrewsbury and Aberystwyth, Arriva Trains Wales has revealed.

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Leaves on the line has been a common complaint, but in 1991 British Rail blamed the “wrong type of snow” for the delay to trains.

Well, there’s a surprise, yet again, the media in its attempt to create a facile headline trundles out the “wrong type of snow” myth. There never was any “wrong type of snow”. That was an invention created by the media in its ongoing attempt to demonise and ridicule the rail industry. Interestingly, in so doing, it does exactly that to the media itself, which gains a well deserved reputation for disingenuous reporting.

In 1991, Terry Worrall, then British Rail’s operations director, pointed out that the powdery snow being experienced that winter was blowing into the electrical systems and causing short circuits. There was also a problem with the low temperatures causing freezing of couplings and sliding doors. Each season brings its own peculiar operational difficulties. Spring and early summer causes expansion of the rails resulting in buckling and, sometimes, the insulated rail joints are damaged, causing track circuits to fail. The autumn brings leaf fall. Naturally, people will have seen the cartoons of trains stopped because a leaf is sitting on the line. The reality, however, is rather more sinister.

Leaf mulch once crushed beneath the wheels of a train forms a Teflon-like coating that is not only slippery but is also an electrical insulator. This causes two problems; the low coefficient of friction of the train’s tyres on a surface akin to black ice makes braking somewhat fraught. Anyone who has been in the driving cab of a train while the brakes are full on, the anti-wheelslip mechanism is hissing away and the train is continuing to move with absolutely nothing the driver can do to stop it, will realise just how inherently dangerous this can be. Bad enough trying to stop at a remote station on plain line; the same situation on the approach to a signal protecting a major junction is potentially catastrophic.

Secondly, not only do we have a possible runaway, the mulch, being an insulator can cause the train to disappear from the track circuit, thereby causing the signal protecting the train to clear. Now we have the risk of  two trains in the section and a potential collision.

Now, do you think leaves on the line are a bit of a joke?

Part of the problem lies with modern units. Frequently they are imported from manufacturers who design and build them for a different climate. This is why Virgin Trains ran into difficulties with their Voyager units traversing the Dawlish sea wall. Salt water caused problems with the traction motors that did not occur with the home built designs such as the HST and the BREL built diesel units. There’s a moral there, somewhere.

Now, this summer, we have the pollen story. It doesn’t surprise me in the slightest. Radiators clog up. That a particular area has problems with pollen and a combination of factors leading to failure is entirely plausible:

“Arriva said the gradient on the track at Tallerdig (near Machynlleth), the hot weather and high levels of pollen were to blame. They said pollen had blocked train radiators and they had failed.”

The rail infrastructure is a huge open electrical circuit operating a range of different traction in a variety of weather conditions. Localised failures are bound to happen.

That many of these things did not happen with steam locomotives is due to them not having electrical systems vulnerable to the weather. Also, they burned the mulch and undergrowth. These problems are a consequence of modern “cleaner” traction. So, there you go. Return to steam traction. The railway workers will love that… Just try getting a steamer to haul a train up an incline with a cold boiler.