London Underground and TfL

Dudley Horscroft   04/08/2017 at 15:04

I believe the following is correct. The incident occurred just after 0600 in November - well before dawn - when it was raining heavily. The speed limit at the tunnel entrance was 80 kph, and at the exit 20 kph. There was a warning board 30 m before the curve, but the tram would have had to start full service deceleration 180 m before the board in order to reach 20 kph at the start of the curve. There was no warning display or device in the tunnel to indicate to the driver that it was time to start braking. The driver for some reason - not yet determined - did not start braking in time. How many trams in the UK or overseas, since Croydon tramlink commenced operating, have derailed and turned over due to excessive speed on a curve. I am aware of only one, in Hong Kong, a double deck tram on 3' 6" gauge track. Are there others? I am also aware of at least one occasion when a tram in a foreign country accelerated immediately the front end had exited the curve, with the result that the rear derailed and swept over the adjacent roadway like a whip lash - cannot remember if there were injuries or fatalities. I believe that the combination of factors in Croydon is so unusual that any universal application of AWS or similar would be taking a sledge hammer to crack a nut. The accident was site specific, and the remedy should also be site specific. I suggest there should be a reflective board inside the tunnel at the point where normal service braking should occur - illuminated by the tram's headlights. This should be followed by a speed detection device at a point where braking at a rate halfway between service and emergency braking would be needed to enter the curve safely, with the ability to place a couple of detonators on the track if speed is exceeded. If needed, then a trip arm raised to operate a standard trip which would result in full emergency braking to a halt. Trams are effectively "buses on rails" and should normally be treated as such. Adoption of heavy rail system wide systems such as AWS (UK) or Positive Train Control (USA) would be excessively costly and counter-productive, leading to tramway costs being unduly inflated, fewer tram systems being built, and continued high loss of life from car crashes in cities. "Horses for courses".

Neil Palmer   04/08/2017 at 16:23

Well said Dudley. There's nothing wrong with having a safety culture, until it reaches the point where you go overboard and the cost involved becomes excessive. That will obviously result in abandonment of future Tram/LRT schemes as affordable, and force passengers onto (or to remain using) far more dangerous modes of transport like cars & buses.

Neil Palmer   04/08/2017 at 16:24

Oops: That will obviously result in abandonment of future Tram/LRT schemes as UNaffordable...

Dorian   04/08/2017 at 20:13

Industry-wide measures ought to be evaluated on the basis of industry-wide impacts. As Dudley says, what is needed at Sandilands is a site specific measure. TfL could take a more basic railway engineering action today by re-laying the track to increase the curve radius and thereby reduce the deficiency of cant at Sandilands Jcn within their existing boundary - I know this because I have drafted a wider radius curve on the digital map data. Former BRB civil engineer

Jerry Alderson   05/08/2017 at 19:11

I think the above points are valid and well made. We need the trams to do the *correct* speed not a lower speed. Some say that's just creating a 'nanny state.' More speed limits makes the service less attractive and less economically viable. Increased journey times makes the UK less productive. A value-for-money effective way of running at correct speed is what we need.

Andrew Gwilt   06/08/2017 at 23:10

Still. The Croydon Tramlink tram crash will always be remembered as the worst tram incident for many years and decades to come. Very horrible crash that 7 people died and 51 people injured and the tram was traveling twice the speed when it approached the bend and derailed at dangerous speed. We all know that trams do have a maximum speed of about 65mph and can accelerate from 0 to 30-40mph when leaving the tram stop or tram station and when approaching a a tram stop it slows down to 15mph and 12mph when approaching a sharp bend or curve.

Mark Hare   07/08/2017 at 10:04

Dudley - there was no warning display or device to tell the driver when to brake because braking points form part of the driver's basic route knowledge. The driver would have been aware of where to brake for all speed restrictions and station stops on the route. You say any remedy should be site specific but this incident could have happened anywhere - a driver could become distracted/lose awareness/fall asleep at any point during the journey and it was just unfortunate that it happened at a location where the driver should have been braking for a sharp curve. I don't believe any kind of warning board/sign/reminder at this location will have any impact at all, what would be more useful is some kind of systemwide AWS/ATP speed control that would provide an audible warning of an approaching speed restriction and possibly even apply the brake if the driver takes no action. Clearly both these options would require major investment which will no doubt not be forthcoming. Clearly in this case as the driver lost awareness, a warning sign would most likely have been ignored for reasons as yet unknown. As others have said

Gabriel Oaks   08/08/2017 at 08:57

"There was no warning display or device in the tunnel to indicate to the driver that it was time to start braking". Both tunnel and subsequent cutting are lit and the driver's route knowledge should tell him that he needs to brake as he approaches the end of the tunnel.

John Grant   08/08/2017 at 10:02

The need for that kind of route knowledge is no doubt why driver training takes so long. Roads have count-down markers that show drivers where to brake, so do motor racing circuits. That said, I agree that signs aren't much use if the driver's eyes are closed, and an audible warning would be better.