Proposed features/3rd and 4th rail

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Garry Keenor
Status: Voting (under way)
Proposed by: GazzerK
Tagging: electrified=4th_rail
Applies to: nodeway
Definition: A track electrified with a 4th rail system, with two additional rails on insulators and two shoe pickup by the train, and traction current returning via one of the insulated rails
Drafted on: 2020-06-08
RFC start: 2020-06-09
Vote start: 2020-06-22
Vote end: 2020-07-06

Proposal

4th rail on London Underground. The outer 3rd rail carries +420V while the centre 4th rail carries -210V. Neither of the running rails carries traction current.
4th rail on London Underground. The outer 3rd rail carries +420V while the centre 4th rail carries -210V. Neither of the running rails carries traction current.
3rd rail electrification. This system carries +750V on the outer third rail, and traction current returns via the running rails which are nominally 0V.
3rd rail electrification. This system carries +750V on the outer third rail, and traction current returns via the running rails which are nominally 0V.

It is proposed that the current railway tag electrified=rail is retained and the definition clarified, to make it clear that it is specifically for 3rd rail systems; and to introduce a new value, electrified=4th_rail. This will allow 3rd and 4th rail electrification systems - which are fundamentally different, in both their mechanical and electrical operation - to be correctly identified and differentiated.

In relation to this, better guidance on the use of electrified=yes is proposed; and also a more accurate definition of electrified=contact_line is proposed.

Rationale

The current electrifed=rail tag is designed to capture railway electrification of the ground level contact rail type. These systems use additional rail(s) which are insulated from earth and carry a voltage. Pick-up shoe(s) on the train collect current from one of the rails. In 3rd rail systems, the current returns to the supply though the ordinary running rail(s). In a 4th rail system, a second insulated rail is provided, and current return is via a second set of pickup shoes through to the second insulated rail. "3rd rail" and "4th rail" are universally-recognised terms for these systems.

The two systems are thus quite different in both their electrical operation, and their mechanical layout. However, both systems are currently tagged electrified=rail, and there is no other way to differentiate these two different systems in OSM.

This is primarily a problem for mainland United Kingdom, where we have a significant amount (400 route km) of 4th rail in operation.

Electrified=rail has been left with the existing value to remove the need for large-scale retagging.

Examples

The vast majority of ground level contact rail systems worldwide are 3rd rail. However, the entire 400 route km of the London Undergound network uses 4th rail, as does the (much smaller) Milan Metro line 1.

Tagging

Proposed tagging is as follows. The whole of the electrified=* tagset is shown for context.

Key Value Property Description Default value
electrified yes Electrified - system not specified This tag is to be used when the system of electrification is unknown. Mappers should use electrified=contact_line, rail, 4th_rail, or ground-level_power_supply where they are able to identify the system by use of aerial imagery or other means.
no Not electrified Used for non-electrified tracks.
contact_line Contact line Used for tracks electrified with Overhead Contact Line (OCL) / Overhead Contact System (OCS) / Overhead Line Equipment (OLE)
rail 3rd contact rail Used for tracks electrified with a 3rd rail system, with one additional rail on insulators, using shoe pickup by the train, and traction return via the running rail(s)
4th_rail 4th contact rail Used for tracks electrified with a 4th rail system, with two additional rails on insulators and two shoe pickup by the train, and traction current returning via one of the insulated rails
ground-level_power_supply ground-level power supply Used for tracks electrified with ground-level power supply on Wikipedia.

Applies to

All and part of a way tagged with railway=rail.

Rendering

This proposal provides a handle for renderers to refine rendering based on the type of contact rail in use.

Features/Pages affected

Additions to wiki pages and tables about railways. This proposal does make any changes on to current 3rd rail electrified railways using electrified=rail.

The explanations for electrified=yes and electrified=contact_line do not affect assets using those tags at all - they simply encourage the use of a more definitive value (when it is possible to determine the type of system) and add the industry-standard terminology for contact_line to assist the reader.

External discussions

Discussion of the proposed change with the OpenRailwayMap group.

Comments

Please comment on the discussion page.

Voting

Instructions for voting
  • Log in to the wiki if you are not already logged in.
  • Scroll down to voting and click 'Edit source'. Copy and paste the appropriate code from this table on its own line at the bottom of the text area:
To get this output you type Description
  • I approve this proposal I approve this proposal.
{{vote|yes}} --~~~~
  • I oppose this proposal I oppose this proposal. reason
{{vote|no}} reason --~~~~ Replace reason with your reason(s) for voting no.
  • I abstain from voting but have comments I have comments but abstain from voting on this proposal. comments
{{vote|abstain}} comments --~~~~ If you want don't want to vote but have comments. Replace comments with your comments.

Note: The ~~~~ automatically inserts your name and the current date.


  • I approve this proposal I approve this proposal. --EneaSuper (talk) 11:41, 29 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --MichaelDono (talk) 14:11, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Csmale (talk) 20:18, 22 June 2020 (UTC)
  • I oppose this proposal I oppose this proposal. Proposal from 06.2020 and start voting in same month... give more time for discussions! --Luschi (talk) 20:42, 22 June 2020 (UTC)
Luschi the RFC period started over 2 weeks prior to the start of voting, and the concerns were addressed in the Discussion section of this page as well as on the Tagging mailing list. Do you have any particular concerns with this proposal? --Jeisenbe (talk) 04:18, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Partim (talk) 05:40, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. -- Sierra 7 (talk) 13:01, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Aembleton (talk) 14:07, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Emiriku (talk) 16:53, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Jeisenbe (talk) 20:49, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Pedromorgan (talk) 20:50, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Thomas Wood (talk) 22:24, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Guidaccia (talk) 22:28, 23 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Chuck (talk) 01:42, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Seatsea (talk) 08:54, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --EM311 (talk) 12:27, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Mdeen (talk) 15:50, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Chris2map (talk) 20:15, 24 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Renecha (talk) 20:12, 25 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --AnakinNN (talk) 21:58, 25 June 2020 (UTC)
  • I approve this proposal I approve this proposal. Initially, I preferred deprecating electrified=rail and splitting it up into 3rd_rail and 4th_rail. However this involves lots of unnecessary retagging which convinced me to agree. --Nakaner (talk) 13:07, 26 June 2020 (UTC)
  • I abstain from voting but have comments I have comments but abstain from voting on this proposal. While I personally don't prefer this, I see no need in redefining electrified=rail as this is a proposal on 4th-rail, and any more specific consideration to any other non-overhead above-ground conductor rail electrification system is absent. -- Kovposch (talk) 15:00, 26 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Dakon (talk) 14:37, 28 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --AgusQui (talk) 16:37, 28 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Riiga (talk) 06:12, 29 June 2020 (UTC)
  • I approve this proposal I approve this proposal. --Juan Carlos G F (talk) 22:10, 29 June 2020 (UTC)