High Speed rail crash in China

See: http://www.bbc.co.uk/news/world-asia-pacific-14262276

Apparently China's high speed rail system has been plagued by technical difficulties - although usually after disasters such as this in China/with Chinese owned vehicles - the safety is usually tightened up and dramatically improved - as I would hope would happen in this instance; of course I'm only commenting on the reported management and maintenance as quoted in the article, as nobody knows what has caused this crash yet.

However, it's bizarre to have a bullet train derail - they're one of the safest trains in the world - it will be interesting to see just how they stood up to the forces of impact etc. What is clearly evident from the photos however is the elevated track design - while cheaper than an embankment - isn't going to cut it for crash situations like this. Although situations like this barely occur.

This must have happened very suddenly, and they must be running a lot of trains for ATS to have not been able to re-act in time to the presence of another vehicle.

Surley a powercut could have had detrimental effects on brake performance, so this could have been a major factor in the crash. Im not 100% sure on the braking system of these bullet trains, but I believe they DO use E-P or ECP brakes... So an electric supply actually controls the pneumatic brakes, without the electric supply, apart from dumping brake pressure, and letting the brakes fully engage, the brakes do not function properly!

True, but yet the first train stopped as there was no power.

Brake performance on trains doesn't rely on any power being needed. Rather, without power the train cannot be moved. This is because the brake actuators have a bloody great spring forcing the brake 'on'. The air reservoir (filled by a powered compressor) needs to have enough pressure in it to counteract the spring to allow the brake to come 'off'. In the event of a failure resulting in lack of air pressure, or the driver engaging 'emergency', the full spring pressure comes to bear and results in a full brake application. This will possibly lock the wheels, make sparks fly and cause severe 'wheel flats', but it will certainly stop the train.

Yes, hapened to me once and not only it causes "wheel flats", it also causes black eyes.

pedned wrote:Surley a powercut could have had detrimental effects on brake performance, so this could have been a major factor in the crash. Im not 100% sure on the braking system of these bullet trains, but I believe they DO use E-P or ECP brakes... So an electric supply actually controls the pneumatic brakes, without the electric supply, apart from dumping brake pressure, and letting the brakes fully engage, the brakes do not function properly!

Mr pedned sir, you are totally wrong and don't understand anything about EP braking at all.

As has been said now, it is power that allows the brakes to be released. However many EP valves there are on a brake unit of a train are all closed when energised, thus no flow of air to the brake cylinders and any air remaining is released so the train can roll. The EP valves will de energise open in series to allow a certain amount of air to the brake cylinders depending on what the drivers control demands. In the event of a loss of power all the EP valves will open due to the loss of electromagnetism, causing a maximum brake application with air. The spring loaded system, in the uk at least, is only a parking brake which activates due to low air pressure in the reservoir. I don't know if china uses this as additional protection or even if magnetic brakes are fitted to high speed stock, this is an area I don't cover as nothing I drive has it.

Apparently the authorities tried to suppress media reporting and work a cover-up. The probable failure might point at signalling / safety systems. Either nor working properly, or not fitted to save money. Even quality issues due to corrupt business practices have been suggested in some newspapers. So, there will be blame to be apportioned. Not that the victims and their families will take much solace in that, especially if it takes as long to get to the bottom of it as it did with Potters Bar.

That sounds the most probable cause of this - as clearly the brakes in the train which went into the back of the stationary train hadn't applied either as the signaling system hadn't anticipated it, or the driver couldn't react in time...