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Author Topic: drive_by_sight tram speed  (Read 534 times)

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Offline Freahk

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drive_by_sight tram speed
« on: October 20, 2020, 05:08:47 PM »
The recent discussion about heavy rail tram track speeds reminded me to an old long-standing issue, which is the unlimited drive_by_sight speeed of trams.

In turn of looking at an implementation of heavy-rail speed restrictions on tram tracks, I'd like to have a look at the drive_by_sight speed of trams as well.
Unlimited drive_by_sight speeed of trams doesn't make much sense. In Germany, tram drive by sight speed is limited to 70 km/h. §49.
Additionally, on-road running is restricted to roads maximum speed.
Drive by sight running is not at all allowed in tunnels (except from short ones, whatever that means in detail), as well as on systems that are entirely independant of road traffic (so called U-Bahn, not to be confused with underground stops)

I do not want to simulate it that specifically, as different countries for sure have different laws and it's rather difficult to determine if a line complies to the definitions of U-Bahn or not.

I'd like to tweak the code to restrict the maximum speed in drive by sight to the waytype specific drive_by_sight speed, as well as restricting the maximum speed of roadbound tram tracks to the maximum speed of the road.
Existing speed-limiting factors remain as-is.

Offline Ranran

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Re: drive_by_sight tram speed
« Reply #1 on: October 20, 2020, 05:35:55 PM »
What I find strange about tram is that tram ignores the rules of the road even though it runs on the road. In Japan, trams running on roads follow the rules of the road. Tram cannot ignore the traffic lights at the intersection. Railroad signals basically do not exist until they enter a dedicated track. Trams should act on the road according to the rules of the road, and the drive_by_site speed limit of 35 km/h is slow. (But this is a pakset limitation, in Japan, the tram that runs on the road is limited to 40 km/h by law. Is the speed limit for British trams on the road is 35 km/h? If unlimited is not allowed, it should be possible to set it separately.)
« Last Edit: October 20, 2020, 05:46:06 PM by Ranran »

Offline Freahk

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Re: drive_by_sight tram speed
« Reply #2 on: October 20, 2020, 06:37:29 PM »
No, the speed limit of UK trams running on roads seems to be 50 km/h.
So we can simply define tram tracks as 50 km/h as-is and it will be all right.

All rail vehicles in drive by sight were restricted to the same speed limit of 35 km/h, which required light-rail vehicles to use signals on roadbound tracks.
This was fixed by not applying any drive by sight speed limits to light rail vehicles, which is another issue.
Thus, I suggest differentiated drive by sight speed limits.
I am not yet sure if the speed limit should be specific to vehicles waytype, tracks waytype or constraints, but I tend to use ways waytype, as light rail/heavy rail mixed traffic on normal tracks should not permit LRVs to run faster than heavy rail vehicles.
Note that at least to my plans, heavy rail will be restricted to an even lower speed limit when running on road sections.

Additionally, in many countries, trams are not permitted to exceed the roads speed, so I'd like to implement this feature as well. Not sure if we need a parameter to disable this per dat file. Some paksets (pak128) seem to include tram tracks that represent tracks between roads, instead of on-road tracks, but these are not yet available in extended.

The traffic light issue is a different one.
In principle some kind of tram and road vehicle interference would be nice, for example trams participating in road crossing logics, but that's a very huge effort, I would not target yet.
« Last Edit: October 20, 2020, 06:56:38 PM by Freahk »

Offline Vladki

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Re: drive_by_sight tram speed
« Reply #3 on: October 20, 2020, 07:22:23 PM »
In Czechoslovakia, the rules are - trams obey the road rules when on road, so the limit is 50 km/h (but used to be 60 km/h). On separated track, the top speed is currently 60 km/h, maybe there are some tracks allowing 70 km/h. Anyway the trams used here are usually capable of at most 65 or 70 km/h. I think the restriction is NOT some general restriction on drive by sight, but more a result of the track condition, curvature and tram capability. Tram tunnels here are so short, that there is probably no special rule regarding them.

There is long tram tunnel in Bratislava, and there is end of speed limit sign on the entry, so I assume the same limit as on road applies. (But there seem to be some signalling in place).

The are only two signalled tram tracks in CZ, because they are single tracked, and at least one of them is limited to 60 km/h as well. (And that was reduced to 40 km/h for some time after a tragic accident before proper signalling was installed.)

Metro (underground) in Prague uses permissive signalling, where the permissive signal is for drive by sight limited to 20 km/h. Top speed with lineside signals is 60 km/h, with cab signals 80 km/h.

Normal railway has drive by sight limited to 30 km/h.

@Ranran: unfortunately the behavior of trams ignoring road traffic is given by the game engine and would probably be quite a lot of work to improve. Also given the current bad functionality of traffic lights (especially different behavior of private and player vehicles on congested crossings) I would be very opposed to doing that. That would completely destroy any advantage of trams against buses.

Offline prissi

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Re: drive_by_sight tram speed
« Reply #4 on: October 21, 2020, 12:36:57 PM »
In Germany most Trams have dedicated traffic lights (which can be also followed by buses).

The horizontal bar mean stop, vertical or tilted means free in that direction, and the triangle is permissive. The middle light is often used in conjunction with skip signals (means if the doors are not close at the middle light, the tram/bus signal will not turn to go for that cycle).

Offline Vladki

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Re: drive_by_sight tram speed
« Reply #5 on: October 21, 2020, 01:38:27 PM »
Yes trams have their own signals, but they are often in sync with road traffic. At least in the sense that if cars are allowed in north-south direction, trams in east-west direction have to stop just like other cars. And the simutrans traffic lights can't do much more than that. But simutrans trams happily run over cars with no effect ;)

Offline jamespetts

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Re: drive_by_sight tram speed
« Reply #6 on: November 21, 2020, 12:43:45 PM »
In principle, it should be relatively straightforward to define a separate drive by sight speed for trams, and I can see the benefit of doing this (especially if the default is that the speed is unlimited, so that there would have to be a simuconf.tab revision for this to change).

Having trams follow the rules of the road would require a much more fundamental rewrite of the tram/road/rail way/vehicle movement code, as trams are currently conceived of as rail vehicles moving on rail tracks, and the movement code entirely ignores the underlying roads. It would be possible in theory to remedy this, but it would require a total rewrite of very large parts of the game, which would be an almost unimaginably enormous amount of work.

Offline jamespetts

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Re: drive_by_sight tram speed
« Reply #7 on: November 21, 2020, 01:02:54 PM »
I have now implemented a separate drive by sight speed for trams. In Pak128.Britain-Ex, this is set to 50km/h.

Offline Lieven

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Re: drive_by_sight tram speed
« Reply #8 on: November 21, 2020, 07:44:03 PM »
In France, trams have the absolute priority on the road, the roads are designed to prevent the road users of the tram approach, by switching on red the traffic lignts, or by swtching on a red flashing light, and the road users must to stop. Trams are considerated as trains.

Otherwise, buses that have they're own ways have the same traffic light than trams, and are considerated like them, they're kind of "tire trams" ;)

Offline Vladki

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Re: drive_by_sight tram speed
« Reply #9 on: November 22, 2020, 06:45:04 PM »
In France, trams have the absolute priority on the road, ...
I doubt this was the rule from the beginning. It sounds more like recent (21st century) improvement. Are trams really separated from road traffic absolutely everywhere? What if the street was not wide enough? Did they just remove the tram line?

Offline Lieven

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Re: drive_by_sight tram speed
« Reply #10 on: November 22, 2020, 07:47:57 PM »
In France, almost all the trams networks disappears on the 30s, and were rebuilt from the end of the XX Century, with all the modern adaptations. They're actually less that 10 cases of trams sharing there way. The loy is very clear on this point, tramway always have the priority on the road, and it don't have to respect the road rules. I think, without being sure, that it's the same case in Belgium.

Documents (In french, sorry :-[)

Loy arcticle :
https://www.legifrance.gouv.fr/codes/id/LEGIARTI000006842327/2003-06-22/

Study on shared tram track :
http://www.strmtg.developpement-durable.gouv.fr/IMG/pdf/fi02418_f03_iutcs_tramway_circulation_generale.pdf

Offline prissi

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Re: drive_by_sight tram speed
« Reply #11 on: Yesterday at 01:08:00 AM »
In Nice, the tram shares the road and there is a 30 kph speed limit though. (And the tram goes even slower). Furthermore, you article is on railway level crossings, where indeed also in Germany there is absolute priority.

Also FRance seem to have the same traffic signals for trams as Germany:

Offline Lieven

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Re: drive_by_sight tram speed
« Reply #12 on: Yesterday at 07:21:31 AM »
Yes, I think that tram signals are practically the same in France/Belgium/Germany (less complex in France than in Germany, they're only 4 signs in france : horizontal, vertical, round and flashing round), but the Nice's tram have a 30kph limitation by tram signals, ther're not limited by the road signals.

If you take a closer look to your picture, you'll see that the road have a single light before the cross, it will be a flashing red light when the tram will approach, and the road users must stop when this light is on. The tram signal is here to protect the cross in case of dysfonctionnement of the system.

We have the same case of signals for the BHNS (Bus à Haut Niveau de Service ; High Service Level Bus), they have reserved roads, that cut round abouts, and they are classic traffic lights that protect this cross. Buses have the same traffic lights than trams on they're way.

If you take a closer look to your picture, you'll see that the road have a single light before the cross, it will be a flashing red light when the tram will approach, and the road users must stop when this light is on. The tram signal is here to protect the cross in case of dysfonctionnement of the system.

We have the same case of signals for the BHNS (Bus à Haut Niveau de Service ; High Service Level Bus), they have reserved roads, that cut round abouts, and they are classic traffic lights that protect this cross. Buses have the same traffic lights than trams on they're way.

BHNS round about in Rennes


Article about BHNS round abound adaptations
http://www.cotita.fr/IMG/pdf/BHNS_Cerema.pdf
« Last Edit: Yesterday at 07:59:48 AM by Lieven »

Offline Vladki

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Re: drive_by_sight tram speed
« Reply #13 on: Yesterday at 09:00:16 AM »
In the second link (PDF) - there are clearly shown trams and cars sharing the same way. Also crossings with no signal for tram, and only a stop/give way sign for cars. Illustration 32 : Carrefour en site banal géré par stop à Angers

Offline Lieven

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Re: drive_by_sight tram speed
« Reply #14 on: Yesterday at 09:53:55 AM »
Yep, as I said it, there are some cases of trams sharing there way with cars, but thery're rare. The case you're talking about is a particular one, because the intersection is on a low-frequented area, but the tram still have the priority. ;)