Digging through some stuff in the archives and found some geeky bits and pieces from the Central line's Sandite season, December 2013 and 2014 respectively. Much like the Metropolitan line, the Central line also operates a Rail Adhesion Train (RAT) to assist in the safe operation of passenger trains during the autumn/winter leaf fall season. During the season, there are two 1962 tube stock RATs in service; one 8-car unit based at Ruislip Depot, to serve the West end of the line; and one 5-car unit based at Hainault Depot, to serve the East end of the line.
For those of you still wondering what all the fuss is about, leaf fall is a horrid time of year for driving trains. It's like driving in the rain, but much worse. With rain, we experience the old slip or slide here, but wheel slide protection on newer trains, or adopting a more defensive driving technique on older trains means it's easy to overcome wet weather (drizzle, or similarly patch rain, tends to be the worst to drive in, in my own experience). The problem with leaves on the line, coupled with the classic wet weather experienced here in England during the colder months, is that all those leaves become a hideous "mulch" of a mess, and it's essentially an extra substance on the tracks that doesn't run off like rain water, but causes the train's wheels to slip and slide in a way where there is sometimes absolutely zero rail adhesion between the whole train and track, which could result in a train not being able to stop at a station, or being able to stop when you want it to. The act of wheels locking up at this point too during leaf fall causes unnecessary damage to the wheel sets on the train (the characteristic thud or banging noise, as a result of wheel flats) and metal fatigue the track itself.
I won't go into too much detail about the trains as you've got Google and a plethora of rail forums that could go on until the cows come home on this subject, but the little RATs have massive tubs on board in one of the cars which you will see in one of the pictures (this goes for the A stock RAT too) and those tubs hold some magic stuff called sandite – a mixture of sand, aluminium and a special adhesive - which is applied to the running rails. And hey presto! – it helps to stop Central line and Metropolitan line trains from whizzing through stations unexpectedly. On the Metropolitan line though, it's worth noting that we run at a reduced speed of 40mph (instead of our usual 60mph) between Amersham – Moor Park on the London-bound line whilst leaf fall is in operation, and this is another contingency plan in place to make sure we are able to stop and to limit damage to trains, track and assets.
Anyhow – here endeth the lesson! And just to let you know that these pictures you see are all personal photographs, so they might not be to everyone's tastes, but they'll give you an idea of some of the kit, gizmos and sights we have on our Central line RATs.