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Author Topic: Heavy rail tram track speed is too high  (Read 891 times)

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Offline Matthew

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Heavy rail tram track speed is too high
« on: October 20, 2020, 09:52:49 AM »
In the tram track discussion, James mentioned that heavy rail tram track is "a special type of heavy rail tramway that lacks this [tramway way] constraint to allow construction of heavy rail tramways such as the Weymouth Harbour tramway." It currently has a top speed of 20 km/h.

The Wikipedia article says that "trains on the tramway were 'walked' by railway staff with flags, clearing the route of people and badly parked cars". This can be observed on this video recording (and I would not be surprised if this was the Wikipedian's source):


The track's top speed should therefore be reduced to walking speed (and the video shows that this is being generous, since the train is repeatedly stopped by obstacles). This abstract of a peer reviewed article says that comfortable walking speed for men in their forties is 146cm/s. Commit 730237c therefore reduces the top speed to 5 km/h.

As well as being more accurate, this change may discourage the practice of building heavy-rail tramways in inland town centres, which is an exploit IMHO.

Offline Vladki

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Re: Heavy rail tram track speed is too high
« Reply #1 on: October 20, 2020, 11:08:42 AM »
I think that 5 km/h is really too slow. I have checked videos from Brno, where a similar heavy-reail tramway exists. it is connecting the exhibition grounds, and has very rare rail traffic (1-2x per year). But it goes in the centre of main road. So no problems with parking cars, but a lot of crossings, including two perpendicular crossings with light-rail (regular) tram line. So  it is often slowing down before getting safe clearance. At least in some moments it is going faster than walking. Slow speed may be also due to low maintenance... And on this video you can see also an old steam tram, which is allowed to go much faster than big train. I think that at least 10 km/h should be allowed.
Also I think these slow speeds are due to extreme rarity of trains going this way and so extraordinary safety measures around. 

In Bechyne, CZ, there is a combined bridge for road and heavy-rail, which is governed by normal rail crossing signals, and trains go a bit faster:

Here is a streetview of the bridge end with 10 km/h sign for railway: https://mapy.cz/zakladni?x=14.4788831&y=49.2981100&z=18&pano=1&source=muni&id=1032&pid=62936938&yaw=1.884&fov=1.257&pitch=0.016

Offline freddyhayward

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Re: Heavy rail tram track speed is too high
« Reply #2 on: October 20, 2020, 12:24:52 PM »
I clearly have a conflict of interest here, but you'd need more evidence than that to justify such a drastic reduction in speed.

Offline jonbridg

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Re: Heavy rail tram track speed is too high
« Reply #3 on: October 20, 2020, 02:58:19 PM »
 5km/h is very low. We could compromise at 13km/h (8mph) which was the initial linespeed of the Wisbech & Upwell, an unfenced heavy-rail tramway which often ran in the road through villages (later increased to 19km/h, but probably only off-road).

13km/h was also the limit at most level-crossings of the Weston, Clevedon & Portishead (initially a tramway but later a light railway) although at the longest crossing, in Clevedon town, the limit was 6.4km/h (4mph) and required a man with a flag.

Offline Vladki

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Re: Heavy rail tram track speed is too high
« Reply #4 on: October 20, 2020, 04:09:56 PM »
One more example - Tirano Italy, 15 km/h limit, although this is narrow (1 m) gauge railway. See the sign about 1:15 in this video:

Offline Freahk

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Re: Heavy rail tram track speed is too high
« Reply #5 on: October 20, 2020, 04:40:09 PM »
We got another conflict here, which is light rail/heavy rail shared sections, which was and afaik still is used in some places to serve some industries.
Light rail can go as fast as roads speed there, whilst heavy rail can only use that section with special securance at much lower speeds.

Thus, I'd suggest a general heavy-rail speed limit on tram tracks, which might simply be another simuconf setting.
If that is considered fine, I'll have a look at the code, it shouldn't be a major thing.

Sadly there is no place for real cargo trams in Britain :(

Offline Vladki

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Re: Heavy rail tram track speed is too high
« Reply #6 on: October 20, 2020, 05:34:23 PM »
Sadly there is no place for real cargo trams in Britain :(
Is it really so? I thought that at least around the turn of century there were some. Here in Brno we had cargo trams up to end of March 1967. :-O 

Offline jamespetts

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Re: Heavy rail tram track speed is too high
« Reply #7 on: December 20, 2020, 12:14:10 PM »
Apologies for not having had a chance to look at this in any detail until now.

I note that the sources conflict on what a sensible speed is; 5km/h seems to be governed by conditions specific to Weymouth (and may not have been the speed even at Weymouth in earlier times), so this does not seem sensible. I note other sources refer to 10km/h, 13km/h and 15km/h.

In the absence of a more definitive source (with full analysis as to the specific causal factors for the specific speed limits so that we can deduce which things are representative of the things that we simulate and which are not), I suggest taking the median average of the three historically based speeds, being 13km/h, which I also note is a UK specific source. I will modify the pakset presently to this effect.

As to the code change suggested by Freahk, I am not sure how this would work, since the code itself does not have a concept of light and heavy rail: these are defined in the pakset as way constraints. It would be bad coding practice to write code specific to a particular datum rather than writing more universal code, but I am not sure how the more universal code would work. I also do not know any instances where heavy rail and light rail share the same street running sections and have radically different speed limits.

As to freight trams in the UK, they were definitely a thing:



I have also seen photographs of small steam tank engines (not tram specific engines, but ordinary industrial engines) hauling a few wagons along a tram line between rows of terraced houses as recently as the 1950s, but I cannot find any of those photographs at present.

Offline jamespetts

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Re: Heavy rail tram track speed is too high
« Reply #8 on: December 29, 2020, 11:15:01 AM »
I have found a photograph of the sort of street running that I describe above; this is Huddersfield in 1938:

wyks - ab 0-4-0st in streets of huddersfield on gas works duty by John Law, on Flickr

Offline Matthew

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Re: Heavy rail tram track speed is too high
« Reply #9 on: December 29, 2020, 01:20:08 PM »
Flickr

I have tried to geolocate this picture using UKRailMap and the gasometer but failed so far. The tramway junction where Somerset Road merges into Wakefield Road faces the gasometer at the right angle, but it's probably a bit too low as it appears that the photograph is taken above its ground level.