What would happen if you went a speed in MPH when it was actually in Km/h?

[Brandon]

You don't know who theMcKenzie Brothers are, apparently.

That's right, I never watched nor followed SCTV; I was more intersted in SNL back then.

Rent Strange Brew, eh. 

[1995hoo]

I had never heard of them either. They sound sort of like a non-sports version of Don Cherry, who I view as basically a caricature of Canadian sports fans.

[GCrites]

My folks had an '89 Cutlass with a digital dash. I thought it would be funny if I switched it over to metric when they weren't looking. I switched it back when it started taking forever to get anywhere. It got old fast.

[J N Winkler]

Especially since every border crossing I've seen on the US/Canadian border has a sign about the speed limits being in metric.  I don't know if the UK/French border has similar signage though - it's probably even more necessary there since the speed limit signs are identical (unlike the US/Canada).

It is less necessary between the UK and continental Europe than it would be in North America, simply because speed limits tend not to be signed explicitly unless they are special limits established by local order.  You are expected to educate yourself as to the national speed limits prevailing in a given country before you travel.  On the open road, the national speed limit is what applies when you pass a round white sign that has either a solid black bar or several parallel black lines running diagonally across it.  (In many continental European countries, a town name sign that has the town "cancelled" in red--meaning "You are leaving this town"--is also a NSL sign.)

I believe some British ports have exits with special signs giving metric equivalents for British speed limits, but these are less common than the signs saying "Drive on left" in several languages.

[roadman]

You don't know who theMcKenzie Brothers are, apparently.

That's right, I never watched nor followed SCTV; I was more intersted in SNL back then.

Rent Strange Brew, eh. 

Or check out https://www.youtube.com/watch?v=ssCZWBtwUTI

[J N Winkler]

The UK/Irish land border (between the Republic of Ireland and Northern Ireland) has these signs at all border crossings. Because of the sensitive nature over the status of Northern Ireland, you will NEVER see a sign indicating that you are entering the UK or Ireland. You might see a sign indicating what county you are entering, but you will always see a sign alerting you that speed limits are posted in miles per hour, or km/hr, as applicable. In most cases, that is your one and only indication that you've crossed an international border, as there are no customs/immigration posts because both countries are part of the Common Travel Area.

I visited Ireland, entering and exiting through Northern Ireland, in the summer of 1999.  At that time there were no signs at the border indicating a units conversion because Ireland still signed speed limits in miles per hour--km/h signing came into force in Ireland about ten years later.  You also could expect to see county boundary signs only on major roads.  There were numerous smaller border crossings where the only indication of the boundary was a change in shoulder striping pattern, from thin solid white in NI to thick broken yellow in the Republic.  I stopped at a few of these and searched casually for monumentation, which I never found.

In terms of signing, the border was actually quite similar to the boundary between two American states, where you normally don't expect to see a state welcome sign or even a stateline crossing sign on a minor county road.

And as regards the security situation, the British and Irish dealt with the minor crossings that were of concern to them simply by closing them off, e.g. by putting up barricades and digging trenches across the road.  Major roads often had checkpoints at times when sectarian feeling was running high in NI.  I was stopped at one just south of the border on 10 July:  the "Twailfth," anniversary of the Battle of the Boyne, is a big deal for the Orange lodges and the Protestant paramilitaries.  A garda was screening traffic but he had backup from rifle-toting soldiers in a nearby Irish Army jeep.  I think I was waved through without question or comment because I was driving a car with GB, not NI plates.  (The format and typeface is identical but NI plates at the time had, and may still have, very distinctive letter-digit patterns.)

[SidS1045]

Multiply km/h by .6 to get mph (not exact, but pretty close).

So, 80km/h = 48 mph.

[Pete from Boston]

Multiply km/h by .6 to get mph (not exact, but pretty close).

So, 80km/h = 48 mph.

In reverse, multiply mph by 6, back the decimal point up one place, then add this to the mph to get km/h.

E.g.,

55 mph x 6 = 330

33.0 + 55 = 88 km/h


After a day out of one's measurement zone this can become almost innate (though for many, it's all still anxiety-inducing).

[hbelkins]

Featuring Jeremy's favorite Canadian singer/bassist:

[Duke87]

Somehow I've never really had trouble with metric speed limits

30 = 20
40 = 25
50 = 30
60 = 35/40
70 = 45
80 = 50
90 = 55
100 = 60/65
110 = 70
120 = 75
130 = 80

Done. Easy enough to memorize.

Not to mention that when you see these numbers enough and see what kinds of roads what number is posted on, it becomes very intuitive.


What takes me more time to comprehend is Celsius. That I usually can't figure out without doing math to convert it to Fahrenheit, unless it's a number close to 0 (which I know is 32), close to 37 (which I know is 98), or close to 100 (which I know is 212). See, speed limits are only ever posted in multiples of 10 km/h, so it's easy to just remember them all. With temps, the weather will report it to the degree and thermostats in Canada go to the half degree. Too many different numbers to memorize the conversion for them all.

[english si]

I believe some British ports have exits with special signs giving metric equivalents for British speed limits, but these are less common than the signs saying "Drive on left" in several languages.

AFAICS, it's every one that has a ferry from France, Belgium, the Netherlands, Spain, Norway or Denmark. And the Channel Tunnel.

Here's Plymouth's

But there's normally only one of them, right by the port exit whereas there's many drive on left signs for each port. Kent is littered with them.

I visited Ireland, entering and exiting through Northern Ireland, in the summer of 1999.  At that time there were no signs at the border indicating a units conversion because Ireland still signed speed limits in miles per hour--km/h signing came into force in Ireland about ten years later.  You also could expect to see county boundary signs only on major roads.  There were numerous smaller border crossings where the only indication of the boundary was a change in shoulder striping pattern, from thin solid white in NI to thick broken yellow in the Republic.  I stopped at a few of these and searched casually for monumentation, which I never found.

Given there's so little border monumentation between counties in the British Isles that's hardly surprising (only really signed on main roads). Even the Anglo- Welsh or Scottish border isn't marked other than signs on main roads.

Where its different is that I'm not sure there was even county signage on the main roads until relatively recently, and even then only some of the time. The boundary is well signed with the speed limit signs, but still very few 'Welcome to County Armagh' type signs.

I think I was waved through without question or comment because I was driving a car with GB, not NI plates.  (The format and typeface is identical but NI plates at the time had, and may still have, very distinctive letter-digit patterns.)

Almost certainly why you were waved through. NI plates are a remnant of a separate Irish system dating back to the 1910s, but the Republic has changed its system. They still have plates spare, so have the different format.

[hotdogPi]

What takes me more time to comprehend is Celsius. That I usually can't figure out without doing math to convert it to Fahrenheit, unless it's a number close to 0 (which I know is 32), close to 37 (which I know is 98), or close to 100 (which I know is 212). See, speed limits are only ever posted in multiples of 10 km/h, so it's easy to just remember them all. With temps, the weather will report it to the degree and thermostats in Canada go to the half degree. Too many different numbers to memorize the conversion for them all.

10=50
20=68 (room temperature)
30=86

[mukade]

Although this is a bit more than 1.6X higher speed, you can see it would not be pretty if these vehicles shared the same road. I would guess the train is going 180-200 mph. (skip to minute 39 and watch the video for one minute)

[vdeane]

See, speed limits are only ever posted in multiples of 10 km/h, so it's easy to just remember them all.

Except with advisory limits, which always end in 5 in Quebec.

[tidecat]

Would they think you're foreign or would they think you're mad?     

What if you saw someone driving a speed in km/h that was actually in MPH?  They'll be driving practically half the speed the should be doing.  The result will be a lot of swerving motorists realizing nearly too late how slow that particular vehicle is going.  Unless you're right at the border, I'd think they're drunk, too old to be driving, or just an idiot, more so than thinking if the person was foreign.

I had the misfortune of getting behind someone from Quebec who was doing less than 40 MPH in a 65 MPH zone.  65 MPH * 0.62 KM/M = 40.3 MPH

[1995hoo]

See, speed limits are only ever posted in multiples of 10 km/h, so it's easy to just remember them all.

Except with advisory limits, which always end in 5 in Quebec.

Of course, technically those aren't speed limits.

It's funny, with a few exceptions (I-87 comes to mind) there aren't signs on the US side of the border reminding Canadian drivers of the different measurement in use here. I was thinking to myself that I wonder what that says about American drivers' ignorance about Canada versus Canadian drivers' familiarity with the US (or, alternatively, the respective authorities' assessment of the other country's drivers).

Does Mexico post signs reminding Americans that signs are metric the way the Canadian provinces do?

[NE2]

I was thinking to myself that I wonder what that says about American drivers' ignorance about Canada versus Canadian drivers' familiarity with the US (or, alternatively, the respective authorities' assessment of the other country's drivers).

Or the fact that going 160 in a 100 kph is generally dangerous, while going 40 in a 60 mph is at worst inconsiderate (and only dangerous if other people can't drive).

[corco]

See, speed limits are only ever posted in multiples of 10 km/h, so it's easy to just remember them all.

Except with advisory limits, which always end in 5 in Quebec.

Of course, technically those aren't speed limits.

It's funny, with a few exceptions (I-87 comes to mind) there aren't signs on the US side of the border reminding Canadian drivers of the different measurement in use here. I was thinking to myself that I wonder what that says about American drivers' ignorance about Canada versus Canadian drivers' familiarity with the US (or, alternatively, the respective authorities' assessment of the other country's drivers).

Does Mexico post signs reminding Americans that signs are metric the way the Canadian provinces do?

I'm guessing it's a relic of metrication. Ostensibly the signs were erected when metric was new in Canada and people on both sides of the border just assumed the default speeds were in MPH unless posted in kilometers for some weird reason. The day after Canada went metric, there would have been a need to remind folks that speeds in Canada were in km/h, but no reason to remind drivers that speeds in America were in mph.

Since then, metric is normal in Canada now, but there's only signs on one side of the border because Canada was the one that initially needed the signs, and they've since replaced the signs because they are a helpful guide.

Basically because Canada was the country that changed units, they have the signs to clarify. The original intent of the signs wouldn't have been to say "hey, stupid Americans, we drive in metric up here" but to say "we've recently converted to metric," which may be why the speed limit signs in MPH are still Canadian-style on those signs. Now they serve more of the "hey stupid Americans, we drive in metric up here" purpose, but since that wasn't the original intent they're only on one side of the border and are formatted the way they are.

I'd actually bet that if America went metric, there would be signs on the US side of the border reminding Canadians that speeds are now in metric, at least for a little while, but since at that point both unit systems would be the same they would probably only last one sign cycle before both countries took their signs down.


Mexican speed limit signs have km/h in the sign.

[J N Winkler]

Does Mexico post signs reminding Americans that signs are metric the way the Canadian provinces do?

I'm guessing it's a relic of metrication. Ostensibly the signs were erected when metric was new in Canada and people on both sides of the border just assumed the default speeds were in MPH unless posted in kilometers for some weird reason. The day after Canada went metric, there would have been a need to remind folks that speeds in Canada were in km/h, but no reason to remind drivers that speeds in America were in mph.

(. . .)

Mexican speed limit signs have km/h in the sign.

I think that is part of it.  Another part is that engineering standards in Mexico are different and the budget for highway improvements is much more limited.  Besides unit system advisory signs having even less utility at the margin in Mexico than they do in Canada ("km/h" already explicit in speed limit signs, no recent history of conversion to metric units), they are a lower priority than removing the things that force American drivers to be far more careful in Mexico than they are in the US.  These include overhead sign supports and concrete (!) roadside marker posts with no guardrail protection, no use of breakaway sign supports, no shoulders, paved drainage gullies (cunetas) that start right at the edge of the traveled way, very few railroad crossings with either grade separations or automatic gates, etc.

Canadian driver licensing procedures are closer to European norms than ours.  There is no way to avoid a driving test by supplying a driver-education certificate like there is in many US states (including Kansas), and the driving test itself is stricter and much easier to fail.  The only state I know of where the driving test approximates that of a typical Canadian province in difficulty is California.

[Dr Frankenstein]

And how many vehicles there don't have km/h listed speedometers (even in smaller print for a model from the US)?  Unless someone's driving a very old (40+ years) car; I wouldn't think there would be that much confusion over km/h vs. MPH.

My friend's 1994 Isuzu Amigo does not have a km/h scale at all. They had him order and stick a metric gauge over the dashboard's plexiglas when he moved it to Canada, but it has long been lost. I've never had a problem driving it, I'm quite used to doing the conversion mentally.

When I bring my Canadian car to the U.S., I keep using the metric scale, since the mph scale is tiny and has few lines, making it too inaccurate for my liking. speed × 5/8 is an easy enough conversion if you know your tables.

[PHLBOS]

My friend's 1994 Isuzu Amigo does not have a km/h scale at all.

Assuming that it was one originally built for the U.S. market; that surprises me.  By then (1994), one would've thought that every make & model sold in the U.S. had both listings (km/h in smaller print).

[bulldog1979]

Since 1979-1980; just about every vehicle sold in the North American market has speedometers calibrated in both MPH and km/h.  Even vehicles equipped with digital readouts have the ability to switch from MPH to km/h with a touch of a button.

The only difference is that vehicles sold in the US market have the MPH listed in larger numerals and km/h listed in smaller numerals.  Vehicles sold in the Canadian and Mexican markets are the opposite (km/h is the major display, MPH is the minor display).

My parents' GMC Terrain has an "analog" speedometer that only has one scale on it in addition to the digital readout between the speedometer and tachometer. If you change the settings in the menu from US to metric, the needle in the dial speedometer jumps to the appropriate number, indicating that it's digitally controlled.

[PHLBOS]

Even vehicles equipped with digital readouts have the ability to switch from MPH to km/h with a touch of a button.

My parents' GMC Terrain has an "analog" speedometer that only has one scale on it in addition to the digital readout between the speedometer and tachometer. If you change the settings in the menu from US to metric, the needle in the dial speedometer jumps to the appropriate number, indicating that it's digitally controlled.

That must mean then that your analog speedometer scale is marked up to 220-230 (for km/h listings assuming the speedometer is calibrated to 140 mph equivalent).  That means if one is going 140 mph; the needle will only be postioned only slightly more than half-way.  Is that a correct assumption/assessment?

[Dr Frankenstein]

My friend's 1994 Isuzu Amigo does not have a km/h scale at all.

Assuming that it was one originally built for the U.S. market; that surprises me.  By then (1994), one would've thought that every make & model sold in the U.S. had both listings (km/h in smaller print).

All I know is that it was bought used in Rhode Island, where his family is from.

[misterjimmy]

I would think that if a USA driver tried to take one of those Canadian off-ramps marked with the checkerboard sign "40" at 40mph, a ticket would be the least of that driver's worries...