Reduced tram speed limits

[southern442]

It appears that some tram systems in the UK have been 'slowed down' from 80 km/h to 70 km/h, Croydon and Nottingham for example. I understand that half the Nottingham trams can only do 70 anyway, but is this all due to the Croydon derailment?

It seems like a juvenile knee-jerk reaction to me, as if to say "we aren't going to give the drivers sensible shifts but we will reduce speeds so when they do crash, less damage will be done". I know it might seem a little dramatically cynical but I have always thought there were not as many lessons learnt from that tragedy as there could have been. Is this a permanent change, and is there any more sensible rationale behind it?

 

[edwin_m]

Most European tram networks base their operations on the German standards (BOStrab) which have a maximum of 70km/h for line of sight operation. In total (and even in some individual cities) these networks have far more vehicle-years of service than the entire UK modern tramway provision with very few serious incidents. This acts as good evidence that the principle is safe at that speed.

The UK was a bit of an exception in allowing 80, and I think Croydon may have led to a view that it's taking the principle too far especially as it wouldn't have happened if it hadn't been a line of sight operation. Today a detailed risk assessment would be necessary when trying to go beyond established practice, but I don't know whether the then HMRI did this 20-odd years ago when they developed the UK tramway principles and guidance.

 

[507 001]

It’s nothing to do with Croydon. It’s to do with modern multi section trams not really being capable of more than 70.
On Metrolink we still have many, many line of sight 50mph (80) sections, and they’re going nowhere anytime soon. The difference being, we run Flexity swift vehicles, which are actually designed to run at 50mph (and I believe up to 60mph in other places).

 

[WatcherZero]

Reason speed was reduced at Croydon apart from the section where the accident occurred was the second set of trams they bought, the Stadler Variobahn, arent capable of taking the same bends that the Flexity Swift are and so they have had to reduce the line speed to match.

The reason TfL went with a vehicle that didnt match the line specifications was they wanted them quick so they bought them off the shelf already assembled ahead of schedule for an order in Norway.

 

[edwin_m]

Reason speed was reduced at Croydon apart from the section where the accident occurred was the second set of trams they bought, the Stadler Variobahn, arent capable of taking the same bends that the Flexity Swift are and so they have had to reduce the line speed to match.

The reason TfL went with a vehicle that didnt match the line specifications was they wanted them quick so they bought them off the shelf already assembled ahead of schedule for an order in Norway.

To be fair the Bombardier trams probably weren't their ideal choice either. They were a design for Cologne with minor modifications, but retaining features such as the cab door being on the "wrong" side.

 

[notadriver]

It is only 7 mph more - not a great deal when you consider tfl runs heavy rail underground services at 60 mph quite safely.

 

[rebmcr]

It is only 7 mph more - not a great deal when you consider tfl runs heavy rail underground services at 60 mph quite safely.

That's not even comparing apples and oranges, it's like comparing apples and Byzantine literature.

Vehicle strength, block signalling, trainstop protection, and full overlaps make the speeds not equivalent in the slightest.

 

[southern442]

These replies have been very helpful, thank you. I suppose at the end of the day the only major inconvenience is not being able to take as good shots of trams at speed as before

Reason speed was reduced at Croydon apart from the section where the accident occurred was the second set of trams they bought, the Stadler Variobahn, arent capable of taking the same bends that the Flexity Swift are and so they have had to reduce the line speed to match.

I find that strange considering the section length of the Variobahns are much shorter, I would've thought that they could take tighter curves. Then again, in my personal opinion the CR4000s seem a lot more heavy duty and well-built than the newer trams.

 

[edwin_m]

Reason speed was reduced at Croydon apart from the section where the accident occurred was the second set of trams they bought, the Stadler Variobahn, arent capable of taking the same bends that the Flexity Swift are and so they have had to reduce the line speed to match.

I find that strange considering the section length of the Variobahns are much shorter, I would've thought that they could take tighter curves. Then again, in my personal opinion the CR4000s seem a lot more heavy duty and well-built than the newer trams.

Coming back to the previous post about Metrolink, I think it's more that the tram designs with wheels moreorless rigidly fixed to short body sections are less compatible with faster running than those with longer body shells and traditional rotating bogies. It might be to do with instability of the body sections at high speeds, compared with a rotating bogie where oscillations can be damped more easily. Curving ability wouldn't affect top speed as any significant curves would be speed restricted.

The multi-section trams do have the advantage of less overhang on curves. In Nottingham this allows an acceptable stepping distance at curved platforms.

 

[craigybagel]

Going from a different thread, Sheffield Supertram has also dropped its top speed from 50mph to 40mph (apart from the Tram Train) - apparently because of track conditions - meaning that Manchester is now the only 50mph/80kmh tramway.

 

[notadriver]

Interesting. Where did you find about this and how do they plan to enforce it ?

 

[TC60054]

Interesting. Where did you find about this and how do they plan to enforce it ?

It’d be enforced in the same way that any other speed limit is enforced.