Why do some tramways use kmph rather than mph?

[507 001]

But for trams safer to show km/h on diamond signs on shared sections so not to confuse motorists

It doesn’t though…

 

[Boff]

A trip to a medical facility will reveal 1 and 3 are metric. Distances, only really roads and even then it's only certain signs , Certain liquids, again only in certain very limited circumstances. Speeds : not all speeds.

You buy fuel for a car in metric, but measure distance of the car in imperial. The mapping of the country is divided into metric blocks, but the road signs in imperial. You're not allowed to drink alcoholic drinks whilst driving which are sold in imperial units, but you are a soft drink sold in a metric container.

Sorry, I think I came across a bit binary - I (and I'm pretty sure the majority of the people on the forum) understand that the UK is in a weird hybrid state between metric and imperial. However, the measurement of speeds when it comes to roads is in mph, and - as outlined by other members - would be really costly to change for little benefit.

Thanks for all the responses though, it does seem logical that it is in the pursuit of switching to a metric system, despite resulting in the slightly odd arrangement of two systems on the same road.

Though I'm still curious how the Tyne and Wear Metro works when sharing track with mainline trains on the way to Sunderland - are there two signs like on roads, but this time one for trains and one for trams?

 

[cool110]

Though I'm still curious how the Tyne and Wear Metro works when sharing track with mainline trains on the way to Sunderland - are there two signs like on roads, but this time one for trains and one for trams?

Yes, being much lighter than mainline trains the Metrocars get a set of differential speeds. The main difference being that instead of being marked with letters they use a stretched hexagonal sign.

 

[blueberry11]

I mean, at the new Edinburgh Trams extension over here, I can see a 20 mph sign for cars and a 30 km/h sign for trams, located at the same pole. They are about the same speed.

Also, the Tramways and Principle Guidance 7.57 states that

The maximum permitted speed of a tram on a carriageway shared with other road traffic should be approximately the same as, or lower than that for other highway traffic.

And weirdly enough, Know Your Traffic Signs page 34, states that the

Speed limit sign for tram drivers [are] shown in kilometres per hour

despite the fact that Manchester and Sheffield both use miles per hour.

 

[Wolfie]

What good reasons are there to change? Apart from the fact that people are used to miles, making the switch would be very costly. We seem to be at a point in this country where there’s barely money for essential stuff, so we certainly don’t need to be wasting money changing something that works perfectly well.

Probably because just about everyone who is 60 or under were, quite sensibly, educated in metric.

The reasons for radical and irreversible change are compelling and unarguable. We should exclusively use SI and metric units.

I was born in the early 1970s and was never taught how to deal with ludicrous mediaeval measurements which operate in multiples of 7, 12, or 13 and seven sixteenths. Let alone chains and fathoms. Get over your grief for and forget your backward-looking nonsense.

I was born on the early 60s. I was given minimal education in dinosaur measurement systems.

 

[bramling]

The reasons for radical and irreversible change are compelling and unarguable. We should exclusively use SI and metric units.

I was born in the early 1970s and was never taught how to deal with ludicrous mediaeval measurements which operate in multiples of 7, 12, or 13 and seven sixteenths. Let alone chains and fathoms. Get over your grief for and forget your backward-looking nonsense.

It’s hardly backward-looking, as mph is what we have now.

I was never taught imperial measurements, however it doesn’t take long to learn.

If we were starting from scratch then yes it would probably make total sense to go with kph. We are not starting from scratch and never will be, hence why the majority of people don’t want to change it. Nothing to do with “being British” or whatever, everything to do with not wanting to waste shed loads of money on changing something that works perfectly well and most people are comfortable with. If it is such a salient thing for some people then there’s plenty of countries they could choose to move to?

Probably because just about everyone who is 60 or under were, quite sensibly, educated in metric.


I was born on the early 60s. I was given minimal education in dinosaur measurement systems.

And yet with that minimal education in it, presumably you manage to get along perfectly well?

It’s all a bit moot anyway as this is something which is probably unlikely to change now. I can’t see the whole road network being changed, and as long as that remains the case miles will remain relevant. And I can’t really see the railway ditching their miles and chains either.

 

[Greybeard33]

Sorry, I think I came across a bit binary - I (and I'm pretty sure the majority of the people on the forum) understand that the UK is in a weird hybrid state between metric and imperial. However, the measurement of speeds when it comes to roads is in mph, and - as outlined by other members - would be really costly to change for little benefit.

The weird hybrid system throws up some bizarre anomalies. We still use miles per (imperial) gallon for road vehicle fuel economy, but dispense fuel in litres. Car displays can be switched from miles + gallons to kilometres + litres, but you cannot have miles + litres. If you want to calculate how many litres of fuel your car needs for a trip, you have to multiply by 4.55!

 

[Wolfie]

The weird hybrid system throws up some bizarre anomalies. We still use miles per (imperial) gallon for road vehicle fuel economy, but dispense fuel in litres. Car displays can be switched from miles + gallons to kilometres + litres, but you cannot have miles + litres. If you want to calculate how many litres of fuel your car needs for a trip, you have to multiply by 4.55!

Yup because the rest of the world isn't going to spend money humouring our eccentricity (at best).

 

[renegademaster]

Probably because just about everyone who is 60 or under were, quite sensibly, educated in metric.

You dont need to know how many yards are in a mile to use a speedo. Plus almost all modern cars have screens instead of a physical speedo which can be switched to Mph with a few taps, it's not a barrier to European drivers either

 

[Basil Jet]

True, I was at junior school 1972-1976 and we had new metric rulers, and some new metric metre sticks and trundle wheels (but not enough so the old yard sticks were still stacked, but not supposed to be used.

No one has been taught old imperial system for half a century, have to pick bits of it up. I am 60 this year but wouldn't know what a dram weight or bushel or furlong actually feels like

The "New Maths" which was 100% metric was taught to kids born after Aug 31 1964 - you were the first year of this. However, subsequent revisions have brought imperial measures back into the education system, and I think kids today are taught both, but I have no idea in which decade that changed.

 

[renegademaster]

The "New Maths" which was 100% metric was taught to kids born after Aug 31 1964 - you were the first year of this. However, subsequent revisions have brought imperial measures back into the education system, and I think kids today are taught both, but I have no idea in which decade that changed.

Theirs a short part in the GCSE spec to convert between cm and inch but I think the intention is more to teach how to convert units rather than learning imperial, you always get the conversion on the paper and it's not something they have to remeber

 

[JJmoogle]

When I was at school in the North West, I learnt a lot of imperial, moved down south, suddenly those measurements are 'archaic and we don't teach or use them'

That was 2001 so not 'that' long ago, I still struggle with a bunch of conversions, we're rather off the topic of why some of the trams use Imperial although I guess it might be notable that I got taught imperial 'up north' so recently and the two tramways still using it are the northern ones.

 

[renegademaster]

When I was at school in the North West, I learnt a lot of imperial, moved down south, suddenly those measurements are 'archaic and we don't teach or use them'

That was 2001 so not 'that' long ago, I still struggle with a bunch of conversions, we're rather off the topic of why some of the trams use Imperial although I guess it might be notable that I got taught imperial 'up north' so recently and the two tramways still using it are the northern ones.

They are also the only two which share track with National Rail

 

[bramling]

Yup because the rest of the world isn't going to spend money humouring our eccentricity (at best).

It isn’t eccentric. We have it because it’s what we have been bequeathed, and it works well enough that it isn’t worth the significant bother of changing it when we don’t really need to.

 

[TRAX]

Can't speak for any other companies but at Edinburgh Trams they are made by CAF in Spain and in Spain the roads are all in kph.

That’s not how it works otherwise all non-UK-built cars would be in kph, no ??

+ other tram systems in the UK use kph

 

[py_megapixel]

They are also the only two which share track with National Rail

Metrolink doesn't share track with Network Rail - the Metrolink routes that were previously mainline ones were converted for the exclusive use of trams

 

[AM9]

The UK already uses metric. It's already switched.

The UK is a combined system.

You buy fuel for a car in metric, but measure distance of the car in imperial.

The fuel for road vehicles is measured in litres (metric), The fuel consumption is measured in litres per 100km (metric) but also given in miles per gallon (imperial) for those that haven't learnt how to use the metric measure (yet).
Soon, virtually all road vehicles will be 'fuelled' by electricity as in kWh, which is neither metric or imperial, but is a global standard of energy, so all this gallons rubbish (defined as 277.274 cubic inches so not really imperial) will fade away.

 

[renegademaster]

Metrolink doesn't share track with Network Rail - the Metrolink routes that were previously mainline ones were converted for the exclusive use of trams

I thought the Bury line at least had some controlled by NR , I remember when RMT signallers where on strike it was suspended

Edit: it was the end of the Altrincham line is signaled by Network rail due to NR and Metrolink tracks running side by side and sharing level crossings

 

[cool110]

I thought the Bury line at least had some controlled by NR , I remember when RMT signallers where on strike it was suspended

You might be thinking of Altrincham where they run parallel, NR signallers need to operate the level crossings for both trains and trams.

 

[Mojo]

Probably just as well that Sheffield uses imperial, given that part of it is tram/train, sharing some track with the -imperial apart from HS1 - national rail network. In Nottingham the tram network is metric but it only runs alongside the national rail tracks, it doesn't share them or connect to them.

Also, on a separate note, what system does the Sheffield Supertram use, and if the Tyne and Wear metro uses kmph what happens when it shares track with mainline trains?

Sharing tracks with Network Rail is not a barrier, as the Tyne and Wear Metro proves, which has hexagonal signs suffixed with "kmh" alongside the usual round signs displaying the limit in miles per hour. Picture of an example from Wikipedia: https://en.wikipedia.org/wiki/File:Tyne_and_Wear_Metro_and_National_Rail_speed_limits.jpg

You also have signs with a black background around the Cambrian and HS1/Channel Tunnel which display speeds in km/h. Picture of an example: https://www.geograph.org.uk/photo/4925871

 

[norbitonflyer]

Also this means that buses usually overtake trams, as (at least in Edinburgh) trams run at up to 30kmph on streets, but busses can run a little bit faster at 20mph. (this really isn't an actual issue, just a bugbear of mine)

Rubber tyres on tarmac can stop faster than steel wheel on steel raikl, and buses can take avoiding actions that trams can't, so maybe a lower speed limit for trams is no bad thing. (Although an important issue for both is the safety of standing passengers in an emergency stop)

 

[AM9]

Rubber tyres on tarmac can stop faster than steel wheel on steel raikl, and buses can take avoiding actions that trams can't, so maybe a lower speed limit for trams is no bad thing. (Although an important issue for both is the safety of standing passengers in an emergency stop)

How does rubber on tarmac compare with steel wheels on steel rails with magnetic track brakes (in and out of the rain)?

 

[philthetube]

What good reasons are there to change? Apart from the fact that people are used to miles, making the switch would be very costly. We seem to be at a point in this country where there’s barely money for essential stuff, so we certainly don’t need to be wasting money changing something that works perfectly well.

That’s the main reason why the road network retained miles when weights and measures were changed. Tram networks are different as they employ people with specialist training (and as pointed out elsewhere have dedicated speed limit signs etc) so these considerations do not apply.

London Underground stuck to MPH when the S stock was introduced for the above reasons.

 

[norbitonflyer]

The SI unit of speed is m/s not km/h. The conversion factor is 3.6....

or 2.23 to convert m/s to mph.

Using metres/second actually makes some kind of sense from a road safety point of view - if people realised that if you look away for 2 seconds at the legal speed limit you will have travelled the length of five buses, they might be a bit more attentive.

 

[Greybeard33]

Rubber tyres on tarmac can stop faster than steel wheel on steel raikl, and buses can take avoiding actions that trams can't, so maybe a lower speed limit for trams is no bad thing. (Although an important issue for both is the safety of standing passengers in an emergency stop)

Trams have magnetic track brakes for emergency stops. 2.54m/s² deceleration for the Metrolink M5000s, even in the wet.

 

[typefish]

The UK has already switched to the metric system, with only limited exceptions.

I disagree, the UK is fully metric. Even the mile is an exact metric measurement.

 

[simonw]

I disagree, the UK is fully metric. Even the mile is an exact metric measurement.

All imperial units are defined by metric measures. That is not the same as saying the UK is fully metric.

 

[AM9]

All imperial units are defined by metric measures. That is not the same as saying the UK is fully metric.

Yes it is because any residual imperial units are defined in SI units, - the mile is no longer 1000 Roman paces, the pound is no longer a lump of metal and light intensity has nothing to do with a particular candle that once existed. Non-metric units are only tolerated because a (rapidly diminishing) proportion of the population have difficulty with basic metric measurements despite them involving difficult calculations using decimal numbers.

 

[The exile]

Yes it is because any residual imperial units are defined in SI units, - the mile is no longer 1000 Roman paces, the pound is no longer a lump of metal and light intensity has nothing to do with a particular candle that once existed. Non-metric units are only tolerated because a (rapidly diminishing) proportion of the population have difficulty with basic metric measurements despite them involving difficult calculations using decimal numbers.

Non metric units are tolerated because
A) you cannot legislate inside people’s heads, so “old habits” will die hard. (There are still surviving elements of pre-metric measures to be found on the continent decades/ centuries after metrication - just look at the contents of a jar of jam!)
B) because of the cost / safety element of conversion. Changing milk bottles to metric in the 1970s would have killed off many independent dairies - likewise beer glasses etc (note that spirits did go metric). Changing road speed limits is a conversion on a scale almost comparable to changing to driving on the right in the sense that it can’t be done in drive and drabs, so no one has yet dared.

 

[simonw]

Yes it is because any residual imperial units are defined in SI units, - the mile is no longer 1000 Roman paces, the pound is no longer a lump of metal and light intensity has nothing to do with a particular candle that once existed. Non-metric units are only tolerated because a (rapidly diminishing) proportion of the population have difficulty with basic metric measurements despite them involving difficult calculations using decimal numbers.

Personally I think the country should have gone fully metric decades ago. But you appear not to have read what I wrote. My opening sentence states that all imperial units are defined by metric measures and yet you repeat a version of these words as if I had said something else.