120 km/h here in Ireland.
Well, as Maastricht already mentioned, here in Germany we have the autobahn with (theoretically) no speed limit at all; in reality this only applies to about half of the network, about 6000 km. So it can happen that you overtake a slow car driving 160 km/h while seeing a Porsche rapidly approaching with 250 km/h in the mirror. But all in all, the autobahn is not the hotbed of insanity one might imagine, though driving on our neighbor’s highways (I often drive in the Netherlands and Belgium) is more relaxed.
Well - in NS the controlled access highways are 110. I forget NB. QC - I drove the width of the province this summer and I’m pretty sure it was 100 all the way. I live in ON, and I can’t recall seeing a 110 anywhere - certainly the Toronto area and east to Montreal along the 401 is 100. Don’t recall MB and SK, but AB is 110 in the controlled access highways. BC - don’t drive enough outside Vancouver to comment.
I regularly go past police cars on the 400 series highways at 120 km/hr and have never been stopped. But of course, like 90% of drivers, I’m above average in my ability, so it’s OK. 
Of course:)
In Spain the official limit is 120km/h on the fastest roads but, due to a judicial decision, there’s always a 10% margin before the cops can fine you, so the effective limit gets treated as 132km/h. I know quite a few guys who were terribly surprised that no, 135km/h does not get “rounded down”.
Montana, a couple of decades ago, had no numerical speed limits. This was often misinterpreted as no speed limits at all, which is why they ended the experiment. There was actually still a limit, but it was just expressed as “a reasonable and prudent speed”.
All 120 km/h roads drop to 100 km/h during winter - for the 100 km/h roads, I think it varies and some drop to 80 km/h while others stay at 100 km/h. I could be wrong, it’s over 10 years since I last drove a car regularly.
ETA - went looking and found some news that confirm that and added that some 80 km/h narrow roads drop to 70 km/h during winter as well.
What kind of roadsign do you have for “no speed limit” ?
(only half joking)
Just a regular sign ending the previous limit. IIRC on Stuart there is a limited section around each intersection, so the sign is effective in each case.
On the Autobahn this is assumed to be common knowledge. People crossing the border pass a sign, and there is a sticker in rental cars telling you that 130 is only recommended, not a hard limit.
I’n Oman it’s 125 kmh (77.7 mph).
New Brunswick is 110 kph on major highways and 90-100 kph on the smaller roads.
I seem to recall a few 120 kph signs just after passing through Quebec.
Note that this only means previous a-typical restrictions are over. In Germany that means: drive whatever you want. But in other European countries it means: the “normal” maximum applies again. In Europe you have signs at the border indicating the speed limits for certain types of roads (high way, regional, city) and you’re supposed to know to keep to them.
I personally find that there is plenty of opportunity to drive 150/160kmh in Germany, just like I get up to 130kmh often enough in Holland as well.
Caution. This only applies to the autobahn. On other roads, the regular speed limit is 100 km/h (50 km/h in cities and villages).
What nonsense! Yes, the speed limit on Ontario 400 series freeways is 100 km/h, and usually 80 km/h on highways that are not limited-access. But just a few hours ago I was doing a steady 120 in the middle lane of a 400-series highway behind several cars doing the same. Then I noticed that there was a cop behind us doing the same speed. He pulled out into the passing lane and passed us all doing at least 130. We kept going at 120. I have also encountered radar traps when I was doing around 120 on 400-series highways with no consequence. No guarantee – YMMV – but this stuff about some new “official” or “unofficial” limit is bunk.
In Japan, the limit on highways is 80 km/h. Camera traps will snap your picture for a stiff fine at 110 km/h and over.
Here in California, the speed limit on highways varies from 55 to 75 MPH,depending on location…for passenger cars . For commercial trucks, and for all vehicles with trailers, the limit is always 55.
This and some other countries speed limits surprises me because the countries are small and the distances between points is much less.
Here in parts of the US like Montana one can be 50 miles between towns with little traffic so those areas were one of the first to drop the old 55 mph law. On the east coast where cities are closer together there was less of a need.
Though you probably wouldn’t guess this from the behavior of drivers.
But it is occasionally enforced. A friend told me he was nabbed for 65mph with a trailer, and it led to an $1100/yr insurance surcharge (lasts 5 years). Nasty.
Somewhat off-topic, but this isn’t quite true. They mostly went back to numerical speed limits due to federal pressure, but also because the state supreme court struck down the “reasonable and prudent” part of the speed law for being too vague. In terms of highway safety, abolishing and then going back to numerical limits (on the Interstate only BTW) had essentially no measurable effect.
Although speaking of unofficial limits, back during the “reasonable and prudent” days the Highway Patrol made a decision to enforce a de facto 90 MPH speed limit which is still about as fast as you need to be going to get a speeding ticket on a rural Interstate in Montana these days. That’s probably why abolishing the limits didn’t make that much of a difference-- other than the occasional out of state yay-hoo in a sports car, the actual speeds didn’t change that much.
Nitpick: unless something has changed very recently, I think the top limit in California is 70.