Weight limit signs

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Glenn A
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Weight limit signs

Post by Glenn A »

Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
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Re: Weight limit signs

Post by Bomag »

Glenn A wrote: Mon May 31, 2021 15:10 Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
A capitol T is neither tonnes or tons but the SI Unit Tesla, which is why since 2016 all new weight/mass limit signs use the lower case 't'. I would assume the relevant change to metric would be the 1984 RTRA in which case there may be a saving limit for tons in either the 1994 or 2002 TSRGD. Environmental weight limits are aligned with the maximum permitted vehicle weight so apply to an empty vehicle. These were changed on harmonisation which is when the old 17 t limit went to 18 t. For weak bridges and roads its the maximum mass so if access is needed you can use it with a sufficiently empty HGV to be under the limit; it also applies to vehicles not covered by a environmental limit.

As any structural engineer who assesses old bridges will tell you, a ton is 1016kg or 1.6% bigger than a tonne.
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Re: Weight limit signs

Post by Glenn A »

Bomag wrote: Mon May 31, 2021 15:35
Glenn A wrote: Mon May 31, 2021 15:10 Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
A capitol T is neither tonnes or tons but the SI Unit Tesla, which is why since 2016 all new weight/mass limit signs use the lower case 't'. I would assume the relevant change to metric would be the 1984 RTRA in which case there may be a saving limit for tons in either the 1994 or 2002 TSRGD. Environmental weight limits are aligned with the maximum permitted vehicle weight so apply to an empty vehicle. These were changed on harmonisation which is when the old 17 t limit went to 18 t. For weak bridges and roads its the maximum mass so if access is needed you can use it with a sufficiently empty HGV to be under the limit; it also applies to vehicles not covered by a environmental limit.

As any structural engineer who assesses old bridges will tell you, a ton is 1016kg or 1.6% bigger than a tonne.
Thankyou, but it is a long time since I saw the old sign with TONS underneath a number.
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Re: Weight limit signs

Post by Glen »

This one still survives, last time I looked, it's quite possible some other old designs do.
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Having a cuppa
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Re: Weight limit signs

Post by Having a cuppa »

Glenn A wrote: Mon May 31, 2021 15:10 Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
Not sure if this would count, but here are two signs in London which aren't that old and use the 'capital T', possibly representing the imperial ton.

https://www.google.com/maps/@51.4809057 ... 384!8i8192
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Re: Weight limit signs

Post by FosseWay »

Bomag wrote: Mon May 31, 2021 15:35
Glenn A wrote: Mon May 31, 2021 15:10 Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
A capitol T is neither tonnes or tons but the SI Unit Tesla, which is why since 2016 all new weight/mass limit signs use the lower case 't'.
This may seem pedantic, but...

In SI, yes, a capital T is the symbol for tesla (which is spelt with lower-case t as a whole word; Tesla is either the make of car or the engineer Nikola Tesla, who gave his name to both). But that does not mean the letter T cannot be legitimately used for any other unit of measurement outside SI. British/American customary units do not have a consistent system of symbols associated with them; they have abbreviations, which may vary from time to time and place to place. As such, T is a perfectly valid, sensible and legitimate abbreviation of ton(s), and an old sign with 3 T does not constitute a mistake simply because T means something else in a different system entirely. It certainly doesn't mean 3 tesla.

Nowadays, of course, we sign weight limits in metric, and by convention we use t for metric tonnes. But tonnes aren't an SI unit either; if you want to express the mass of 1 cubic metre of water at 4 degrees Celsius in pure SI terms, it's 1 Mg (!). To what extent the great unwashed understands (a) the difference between short tons (2 000 lb), long tons (20 cwt, 1 016 kg) and metric tonnes, and (b) how the abbreviations/symbols T and t relate to those measures, I don't know. I also suspect that a bridge rated to carry 1 tonne is unlikely to fall down if subjected to 1 (long) ton, since the margins of error are surely going to be greater than 1.6%. But in any of that, discussion of teslas (the unit) is entirely irrelevant :wink:
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Re: Weight limit signs

Post by JohnnyMo »

Short ton (2000 lbs) is the default in the US, 20 x 100 lbs (US-cwt)
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Re: Weight limit signs

Post by Vierwielen »

FosseWay wrote: Tue Jun 01, 2021 09:32
Bomag wrote: Mon May 31, 2021 15:35
Glenn A wrote: Mon May 31, 2021 15:10 Do any of the signs with weight limits expressed as 2 TONS rather than 2 T, for example, still exist? I remember these being steadily phased out in the eighties, possibly as a form of metrication as ton is the imperial measurement and T could mean either tons or tonnes( the difference is minimal), and can't recall seeing one for over 15 years.
A capitol T is neither tonnes or tons but the SI Unit Tesla, which is why since 2016 all new weight/mass limit signs use the lower case 't'.
This may seem pedantic, but...

In SI, yes, a capital T is the symbol for tesla (which is spelt with lower-case t as a whole word; Tesla is either the make of car or the engineer Nikola Tesla, who gave his name to both). But that does not mean the letter T cannot be legitimately used for any other unit of measurement outside SI. British/American customary units do not have a consistent system of symbols associated with them; they have abbreviations, which may vary from time to time and place to place. As such, T is a perfectly valid, sensible and legitimate abbreviation of ton(s), and an old sign with 3 T does not constitute a mistake simply because T means something else in a different system entirely. It certainly doesn't mean 3 tesla.

Nowadays, of course, we sign weight limits in metric, and by convention we use t for metric tonnes. But tonnes aren't an SI unit either; if you want to express the mass of 1 cubic metre of water at 4 degrees Celsius in pure SI terms, it's 1 Mg (!). To what extent the great unwashed understands (a) the difference between short tons (2 000 lb), long tons (20 cwt, 1 016 kg) and metric tonnes, and (b) how the abbreviations/symbols T and t relate to those measures, I don't know. I also suspect that a bridge rated to carry 1 tonne is unlikely to fall down if subjected to 1 (long) ton, since the margins of error are surely going to be greater than 1.6%. But in any of that, discussion of teslas (the unit) is entirely irrelevant :wink:
According to table 8 of the SI Brochure, the "tonne" is a "Non-SI units accepted for use with the SI Units". See the brochure for more details. Note that the link points to a bi-lingual version of the SI Brochure.
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Re: Weight limit signs

Post by AndyB »

A capital T on a road sign refers to tonnes, not the imperial measure (always TONS). Nobody ever thought that it meant Teslas, but lower case t is not only technically correct but the international norm on road signage.

The 1.6% difference between a tonnne and a ton is significant to an engineer, but is of the order of the difference between 1.6km and a mile to a layman (0.5% to an engineer). However, if the TRO states 3 tons, a vehicle weighing 3048 kilograms can still lawfully pass a sign stating 3 tonnes without needing to consider de minimis.
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Re: Weight limit signs

Post by Bryn666 »

AndyB wrote: Tue Jun 08, 2021 11:40 A capital T on a road sign refers to tonnes, not the imperial measure (always TONS). Nobody ever thought that it meant Teslas, but lower case t is not only technically correct but the international norm on road signage.

The 1.6% difference between a tonnne and a ton is significant to an engineer, but is of the order of the difference between 1.6km and a mile to a layman (0.5% to an engineer). However, if the TRO states 3 tons, a vehicle weighing 3048 kilograms can still lawfully pass a sign stating 3 tonnes without needing to consider de minimis.
The real issue is why are potentially safety critical and thus significant restriction signs that were phased out 40 years ago still hanging on - if the signs still hang on it implies the last time anyone did a bridge survey was sometime prior to 1981...
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Re: Weight limit signs

Post by AndyB »

And you’re surprised? :D
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Re: Weight limit signs

Post by Bryn666 »

AndyB wrote: Tue Jun 08, 2021 13:59 And you’re surprised? :D
Oh not at all, but :shock: :shock: :shock:
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Re: Weight limit signs

Post by WHBM »

FosseWay wrote: Tue Jun 01, 2021 09:32 To what extent the great unwashed understands (a) the difference between short tons (2 000 lb), long tons (20 cwt, 1 016 kg) and metric tonnes, and (b) how the abbreviations/symbols T and t relate to those measures, I don't know.
Now I've had a shower this morning, but although knowing what the differences are, it's one of life's conveniences that the US ton (where they very sensibly moved away from a hundredweight actually being a hundredandtwelveweight, the UK ton, and 1,000kg are sufficiently close to one another that it doesn't matter ...
A capitol T is neither tonnes or tons but the SI Unit Tesla
A Capitol is surely none of the above but a USA administrative building :)
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