Sunday, 28 May 2017

British Airways Computer Crash

It is very alarming that the British Airways computer crash on Saturday 27th May 2017 shut down its entire operation. Apparently it was due to a power failure. That there was no back up power supply or UPS (Uninterruptible Power Supply) as it is called, is remarkable. That a major international transport system, with a world wide network of routes, can run its operation on a single, interconnected system technology without any backup system, demonstrates a serious lack of management responsibility. And, it has serious implications for the railway industry.

Normally a vital operation will have a some sort of back up or UPS to provide business continuity. But, consider this: if a system is vital and safety related, it needs to have a UPS. This will come into action when the main power system fails so that the operation keeps going. However, there is a trend nowadays that says, "If the UPS isn't available, the main system shouldn't be allowed to start up." And, "If the UPS fails, the main system must be shut down because it doesn't have a working backup." This is crazy. If this is your designer's philosophy, then you don't need a backup because it will eventually shut down your operation whenever it fails.

Railway signalling and train control systems are going the same way.

Saturday, 13 May 2017

Cyber Attacks

With all the news on cyber attacks around the world, this article from London Reconnections is worth a read: You Hacked. It looks at some attacks that have been carried out on railway systems and offers a warning.

Friday, 12 May 2017

Braking Curve

In railway engineering, you will sometimes hear talk of a "braking curve", often in connection with train performance, platform re-occupation times or signalling. We use a braking curve to calculate how long it will take a train to stop from a given speed. It can be used to determine both service and emergency braking distances. It can also give braking times, if needed. Here we look briefly at the braking curve and what it means.

The braking curve is the shape formed on a speed/distance chart by a train as it slows down from normal speed to a stop.  A typical curve looks like this:

The curve begins when the driver applies the brake. The brake system take a few seconds to build up to the required braking rate (the "feed up" time) and then the train begins to slow down.

With a constant brake demand, as selected by the driver, the train slows down more rapidly as the speed falls. This is because, at the lower speed, the train has less energy to dispose of. If the brake is left on at the same level all through the stop, eventually the curve will get steeper and steeper until it ends vertically at the stop. If this is allowed to happen, the train will stop with a sharp bump and a lot of coffee will be spilt. To prevent it, a skilled driver will ease off the brake as the speed falls and this will allow him to stop the train gently. The effect of this can be seen on our curve as it nears the stopping point.

Our drawing also shows an "equivalent straight line" curve. This is a simple way of showing the stopping distance that we can expect a train to cover, given an equivalent deceleration rate. It can be used to calculate stopping distances for approximate signalling calculations, for example, although today, computer programs make accurate and detailed calculations simple. The straight line braking curve can used, for example, for outline planning or to demonstrate principles.

Report on Rail Franchising in Britain

A report on railway franchising in Britain was published in early May 2017, 'Ensuring a Sustainable Rail Industry - Options for developing franchised passenger services', published by the Campaign for Better Transport. It is an interesting read, partly because it has some useful statistics about rail travel, franchise operations and passenger attitudes and partly because it tries to generate debate on the industry and the way in which it is run.

The report notes that passenger "trust" in the railway is falling and it suggests that this is causing, in part at least, a slowdown in the increase in traffic seen over the last 20 years. It also suggests that the issue is partly due to the franchising model itself, which doesn't encourage quality.

There is also justified criticism of the complexity of the fares systems and the difficulties that they present to passengers. I do not understand why we can't have contactless ticketing across the country.

There are some omissions:

  • There is no mention of staffing problems and the recent series of politically driven strikes;
  • There is no realisation that the capacity constraints that are causing a fall in punctuality;
  • There is no mention of the responsibilities of Network Rail in the performance model;
  • There is no understanding that the British, as a nation, generally deride the public transport system;
  • There is a mistaken belief that what has been done on one railway can be applied to any other one with the same results. 
The value in the report is the generation of discussion on the performance of franchised railway operation. It is worth a read.

Friday, 5 May 2017

Railway Technical Website Update

We are modernising the Railway Technical Website. There is a new look and new pages. Many pages are being updated. We are gradually archiving the old pages where they are likely to be useful.

While we will try to get everything in place correctly as we update each page, there are bound to be some minor teething problems. Please let us know if you find any errors we have missed.

Thank you for visiting us and for your understanding during our modernisation programme.