Proposal:Clearance (construction)

Clearance
Proposal status:	Rejected (inactive)
Proposed by:	Skippern
Tagging:	clearance=<numeric>
Applies to:	way,node
Definition:	Since overhead clearance is not covered by height=* and is different from maxheight=*
Statistics:
Draft started:
Proposed on:	2009-07-27
RFC start:	2009-07-29
Vote start:	2009-09-10
Vote end:	2009-09-24

The physical clearance of structures can limit the passage of vehicles, even when no legal restrictions are put in place, but can also be possible to mark together with a legal restriction to indicate how much clearance you have on the legal limit. The passage of vehicles close to the physical clearance can often be much slower than the traffic in general, though legal restrictions might not affect the transit speed.

Definition

To mark the clearance from the ground to a physical barrier limiting the height of the passing vehicles or vessels without inducing a legal restriction. In case of legal restrictions, use maxheight=*. The limitation is to be tagged on the way, not on the structure limiting the passage.

The Proposal

This proposal will leave maxheight=* as is, but offer a few new tags to enhance the information about a height restriction. None of the proposed tags will alter the definition of maxheight, only offer the possibility to map more details of the height restriction. (There are no sure way to verify if existing tagged maxheight refer to legal or physical height, other than if the various signs exists in the various countries - therefore, adding the word legal in the description of maxheight might make some tags wrong)

Legal Height Restriction

maxheight:legal=3.2 to be given a numeric value in meter, or;

maxheight:legal=10 ft to be given a numeric value with notation of units.

Physical Height Restriction

maxheight:physical=3.2 to be given a numeric value in meter, or;

maxheight:physical=10 ft to be given a numeric value with notation of units.

A subnote can be added to maxheight=* stating that there is no indication whether the restriction is physical or legal, the difference between such restrictions might be academic, or unknown for the mapper who did the tagging. This will not deprecate any old tags, and routing engines should use the lesser of these values if several exists for the same way or node.

For marine usage

When marking the free sailing height under bridges, the tag should be maxheight:marine=* and located on the section of the bridge passing over the safe navigational channel as opposed to normal usage.

This follows a different scheme of tagging as marine tags have a different need and purpose than highway tags. Here we are interested in highlighting the danger (the physical bridge structure), but give the captain of the vessel the necessary information to decide whether his vessel can pass or not.

Free sailing height is the distance from chart zero (usually Mean Low Water), up to a section of the bridge the width of the safe passage channel. It is usually rendered as a number (the height in meter) between two horizontal lines.

The marine rendering of maxheight:marine=* might not be of interest on the main map, but can be of much interest to other special interest maps such as OpenSeaMap.

Rendering

No rendering will be suggested as of now, though the two signs (the round restriction sign and the diamond shaped warning sign) with the value could be rendered on special interest maps or through algorithms made available for routing software.

• not yet

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Discuss

Please discuss on the talk page.

See Also

• maxheight=* (the existing restriction)
• height=* (height of structure)
• ele=* (elevation above sealevel)

Voting

Vote with {{vote|yes/no}} ~~~~

Vote is closed.

The vote will be divided in tree, please vote at each when the vote opens.

maxheight:legal=*

Result: 4 yes / 6 no

• I approve this proposal.--Skippern 11:58, 10 September 2009 (UTC)
• I oppose this proposal. -- maxheight=* already covers the legal usage and is in wide spread use, there is no benefit in having 2 tags mean the same thing --Delta foxtrot2 12:21, 10 September 2009 (UTC)
• I oppose this proposal. -- just keep maxheight=* for this, the overwhelming majority of uses will be legal (in most places that's the only information that is signed and maxheight documentation strongly hints at legal interpretation) --Tordanik 13:14, 10 September 2009 (UTC)
• I oppose this proposal. -- maxheight:legal is the same as maxheight so keep the one allready in use --Sergionaranja 13:35, 10 September 2009 (UTC)
• I approve this proposal. -- I like tags whose meaning is explicit without needing to refer to the wiki. This is an improvement over "maxheight", and I don't see why the two can't co-exist peacefully -- Waldo000000 22:47, 10 September 2009 (UTC)
• I approve this proposal. --Cartinus 12:58, 11 September 2009 (UTC)
• I oppose this proposal. -- Should use maxheight for this --Pobice 19:54, 11 September 2009 (UTC)
• I approve this proposal. -- haddock 17:11, 15 September 2009 (UTC)
• I oppose this proposal. Socks 15:19, 16 September 2009 (UTC)
• I oppose this proposal. -- maxheight:legal is the same as maxheight so keep the one allready in use --Dieterdreist 20:07, 16 September 2009 (UTC)

maxheight:physical=*

Result: 7 yes / 3 no

• I approve this proposal. --Skippern 11:58, 10 September 2009 (UTC)
• I approve this proposal. --Delta foxtrot2 12:24, 10 September 2009 (UTC)
• I oppose this proposal. -- if the other two proposals are not approved, then clearance=* is a better name for this. im ok with definition and use. --Sergionaranja 13:35, 10 September 2009 (UTC)
• I approve this proposal. -- Waldo000000 22:47, 10 September 2009 (UTC)
• I approve this proposal. --Cartinus 12:58, 11 September 2009 (UTC)
• I approve this proposal. --Pobice 19:54, 11 September 2009 (UTC)
• I approve this proposal. -- haddock 17:11, 15 September 2009 (UTC)
• I oppose this proposal. Socks 15:19, 16 September 2009 (UTC)
• I approve this proposal. -- Dieterdreist 20:08, 16 September 2009 (UTC)
• I oppose this proposal. -- A physical maxheight is a legal maxheight, if your car does not fit you are not alowed to drive there -- Gnonthgol 18:00, 27 September 2009 (UTC)

maxheight:marine=*

Result: 1 yes / 8 no

• I approve this proposal. --Skippern 11:57, 10 September 2009 (UTC)
• I oppose this proposal. -- this is the same thing as maxheight:physical, and if there is a water way under a bridge we will know it's a marine height --Delta foxtrot2 12:23, 10 September 2009 (UTC)
• I oppose this proposal. -- don't use "maxheight" if it has a different meaning (possible height on a way vs. possible height below a way). Choose a different key name for this (clearance, maybe?) --Tordanik 13:11, 10 September 2009 (UTC)
• I oppose this proposal. -- this is the same thing as maxheight:physical. just make clear how to tag it in the marine context. --Sergionaranja 13:35, 10 September 2009 (UTC)
• I oppose this proposal. -- maxheight should always refer to height above the tagged way. Use something else for this - if you are tagging the "free sailing height below" use, say, free_sailing_height_below! -- Waldo000000 22:47, 10 September 2009 (UTC)
• I oppose this proposal. -- haddock 17:11, 15 September 2009 (UTC)
• I oppose this proposal. Socks 15:19, 16 September 2009 (UTC)
• I oppose this proposal. -- Dieterdreist 20:09, 16 September 2009 (UTC)
• I oppose this proposal. -- This should be taged on the searoute or/and as another tag on the bridge, maybe bridge:height=value or just height=value? The value is altso dependent on the tide witch this proposal does not mention -- Gnonthgol

Some comments on the opposing views to correct some misconceptions: (Feel free to move any point to the discussion page if you want discussion.)

1. Maxheight:physical would be the same as maxheight:marine only if it could be added to a, say, canal section below a bridge; former is for users traveling along the bridge way, latter for users crossing below the bridge way and often there's no single "searoute" below the bridge that could be tagged as (physically) height restricted; the height is not restricted on the whole lake but only in the area below the bridge. Splitting continuous lakes into three abutting areas under each bridge is... well, a decision that I'm sure would get opposition, too.
2. Tide is mentioned; the sailing height is measured "from chart zero, usually mean low water". Sailors already get tide announcements and use them to adjust the height for their use.
3. Height of a bridge is the total height of the structure, not the height of the passage below the bridge. Alv 08:57, 17 September 2009 (UTC)