130kmph instead of 120kmph on motorway

Big Gerry

https://www.boards.ie/discussion/comment/123203972#Comment_123203972

The high cost of petrol is what really stops people from driving over 80mph.

KrisW1001

https://www.boards.ie/discussion/comment/123205474#Comment_123205474

You are well aware that those limits are explicitly conditional on weather conditions, whereas our limit is not.

Reincarnation is supposed to bring one closer to enlightenment...

quantum_technician

https://www.boards.ie/discussion/comment/123206396#Comment_123206396

Well that is incorrect information which you disseminating there but I don't have the time nor inclination to correct you.

Flinty997

France...

"....When raining, the default speed limit on dual carriageway roads is reduced to 100 km/h, and on motorways 110 km/h (or 100 km/h if signposted for a lower dry-weather speed than the 130 km/h default). ..."

There were others but not as clearly stated.

Seth Brundle

https://www.boards.ie/discussion/comment/123206516#Comment_123206516

I corrected you on this two days ago and youre still claiming it is incorrect? Enlighten us with your wisdom so!

quantum_technician

Your comments were related to France so you didn't correct me.

Flinty997

It was made out Ireland was an outlier. With a minimum of fact checking, it obviously isn't.

130km make so little difference to anything considering the short distances in Ireland. But it's tone deaf.

kirving

https://www.boards.ie/discussion/comment/123204692#Comment_123204692

https://www.boards.ie/discussion/comment/123205190#Comment_123205190

There are various implementations depending on the manufacturer. They can use GPS, wheels speed sensors, or even dead reckoning in a tunnel (for GPS calculations, I don't think for speed display)

My car with GPS and a digital dash actually under-reads my speed by about 1mph vs GPS on a straight road with Cruise Control on, but I'm based in the US now. Even cars without GPS/digital dashes are very accurate, and often actually have a programmed offset built in (which can sometimes be coded out), mainly just to compensate for incorrect tyre sizes.

The big catalyst for more accurate speedo's is EV's. A 10% discrepancy between range vs milage would be quickly noticed and be more trouble to explain - so they'll bias toward a GPS reading. In addition, eCall has really mandated that all cars have a GPS receiver built in, even if you don't have Navigation.

KrisW1001

@kirving
All production cars use a rotation sensor for the speedometer display. This is the only way you can have reliable, accurate speed measurement in all conditions. Your sat-nav uses the speedometer as an input for dead-reckoning in loss of signal, not the other way around. And your car’s sat-nav is lying to you pretty much all the time: in low signal-quality conditions, it snaps your position to the most likely road based on your speed and direction of travel. (I used to work with raw GPS traffic data; the actual measurements are all over the place).

As for your speedo, US regulations do appear to allow under-reading - here’s the text, which is remarkably clear for the FMVSS:

“The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).” [eCFR :: 49 CFR 393.82 -- Speedometer.] (Yes, kilometres.. Federal regulations tend to be a mix of both. But all US distance measures are ultimately defined in metric units anyway)

That’s a single-point calibration, of course, so the error could do anything outside that range (it’s usually mostly linear because it’s measured by a rotation-counter).

For comparison, the regulations used in the rest of the world are: 1. never under-report speed; 2. Test at 40, 80, 120 km/h real speed, 3. Car must over-report by no more than 10% real speed + 4km/h (i.e., max “48 km/h” at actual 40, max “92 km/h” at actual 80, max “136 km/h” at actual 120.)

Because the UNECE rules require a 3-point calibration, the actual error ends up being far smaller than the rules allow.

geographica

https://www.boards.ie/discussion/comment/123201040#Comment_123201040

The M50 is 100 no way they’d increase it to 130

chicorytip

https://www.boards.ie/discussion/comment/123206022#Comment_123206022

Average fuel consumption is far less on motorway trips - particularly if the cruise control is engaged - than it tends to be in city and suburban driving, by as much as 10 L per 100 km in my experience. I drive a diesel engined car. Driving long distances at higher speed is not less economical - unless you're exceeding the speed limit by a large margin.

Tenzor07

https://www.boards.ie/discussion/comment/123207144#Comment_123207144

And with very good reason, the M50 is very "Twisty" for a motorway plus it dips and rises in elevation across it's route… not to mention the many exits along it's distance too… we're lucky it's even 100!

magicbastarder

https://www.boards.ie/discussion/comment/123207186#Comment_123207186

generally speaking, once you're in top gear, your fuel efficiency drops off with speed. it's not the case that it holds steady with speed till you exceed the speed limit (i assume you mean 120km/h here) by 'a large margin'.

the inefficiency in stop/start urban traffic comes primarily from the stop/start nature of the traffic, and secondarily from the lower speed.

in my car, peak fuel efficiency seems to happen at around 85 to 90km/h (based on my crude observations).

onedmc

https://www.boards.ie/discussion/comment/123201018#Comment_123201018

I agree, this is hard to police but if there was a distance limit of say 3km on the outside lane. After thart you must pull-in that might make it easier to police.

quantum_technician

https://www.boards.ie/discussion/comment/123206742#Comment_123206742

Are you actually trying to deny that the vast, vast majority of Europe in terms of land mass and population hasn't got a default speed of 130kmph. The fact checking done confirmed my position, not yours.

Denying the Irish the ability to travel at what is considered a safe speed elsewhere is just another example of the deeply ingrained nanny statism that afflicts Ireland

KrisW1001

https://www.boards.ie/discussion/comment/123207263#Comment_123207263

Most passenger cars are geared for maximum efficiency at 80-90 km/h because that's what gives the best results in the "extra urban" cycle of the official fuel consumption test. Every engine has a speed where it's most efficient, and the manufacturer sets up the gearbox ratios so that this speed translates to 80-90 km/h on the road.

Energy use rises exponentially with speed, as you're primarily fighting wind resistance at any speed over 100 km/h. The size of this increase isn't as obvious in combustion engined cars, where around 50% of the fuel you burn is wasted anyway, but in EVs 90% of your stored energy goes into moving the car, so you really notice the difference between 100 and 120.

Rocket_GD

https://www.boards.ie/discussion/comment/123207323#Comment_123207323

This seems like an awful lot of bluster of 10kmph that would cost millions to implement between consultation phases, advertising, changing road signs etc.

Are you really in that much of a rush?

magicbastarder

https://www.boards.ie/discussion/comment/123207338#Comment_123207338

i think i remember james may, when driving the bugatti veyron, claiming that it took 250hp to get it to 155mph, and another 750hp to get it from 155 to 250mph.

quantum_technician

https://www.boards.ie/discussion/comment/123206516#Comment_123206516

Google search for "Bei Nässe Schild" is the missing piece of information which Kris doesn't have at his disposal. Autobahns are of variable quality and construction with various speed limits due to various reasons such as construction material, presence of emergency lanes, lane width, straightness or lack thereof, steep ascents and more importantly descents, proximity to population centres not only for traffic density but also noise pollution but the over-riding concept is that the right speed(Richtgeschwindigkeit) is 130kmph even on unrestricted stretches of road where one may travel faster but with partial blame asssumed should an accident occur.

elperello

https://www.boards.ie/discussion/comment/123207144#Comment_123207144

That's agreed.

They would never go from 100 to 130.

Interestingly the original design speed was 70 mph (112 kph).

Despite upgrades over the years the increased traffic volumes have reduced the limit.

bikeman1

My car speedo reads consistently at 127 / 128 kmh with the digital display for a GPS 120 kmh on a straight open road with different devices. I pop the cruise control at 127kmh and don't go less than or mor than that for as long as possible on long runs. That gets the average speed up, which is what cuts down the journey time.

Raising it to 130kmh is a pointless exercise. Uses a lot more fuel, saves literally a few seconds on the journey overall. Pulling in for one coffee and before you even step out of the car you will have nearly lost most of the time savings on most runs. This idea should be put in the bin as it is a pointless exercise.

Also, our speed limits increased from 70 mph to 75 mph when we switched to kmh, a wise move at the time, but we don't need to go more.

As has been mentioned numerous times, middle lane hoggers or slow overtakers are far more an issue than 120 or 130 kmh.

Flinty997

https://www.boards.ie/discussion/comment/123207134#Comment_123207134

Thanks for that very comprehensive.

Flinty997

https://www.boards.ie/discussion/comment/123207427#Comment_123207427

The overriding concept is you drive to the conditions. 130 is recommendation even where there is no limit. But it's lower in poor weather and visibility.

The difference is they will enforce it. In Ireland they won't. So it's nonsense to just copy rules from somewhere else because you prefer them..

Flinty997

https://www.boards.ie/discussion/comment/123207323#Comment_123207323

So having failed in misrepresentation of number of countries and limits you've now switched to land mass and population size.

Speed limits are across vast empty parts of the world where your lucky to see a goat are irrelevant to Ireland.

What will you try next elevation and colour of tarmac.

Flinty997

https://www.boards.ie/discussion/comment/123207186#Comment_123207186

Already explained by other posters...

"...Generally speaking, the optimum driving speed for fuel economy is 72-80 km/h (increasing your speed from 90 km/h to 120 km/h can raise fuel consumption as much as 20%).."

I remember seeing before there's a big difference between 100 and 120. But it depends on a lot of factors..

magicbastarder

air resistance squares with speed, and at those speeds, air resistance dominates. so increasing your speed by 10% would increase your fuel consumption by over 10%.

dodzy

https://www.boards.ie/discussion/comment/123201165#Comment_123201165

I can guarantee you one thing. Travelling at 130kmh will make your efficient EV very inefficient.

Flinty997

https://www.boards.ie/discussion/comment/123207338#Comment_123207338

You can see the effect of speed on range (for EVs) in apps like abrp. (A better route planner).

Yeah Right

https://www.boards.ie/discussion/comment/123207323#Comment_123207323

What is the population of the countries that use 130 vs the rest?……………..and what is the landmass of those that use 130 vs the rest?

Seeing as you've already made the calculations, that is. I mean, you wouldn't be making that claim without having actually done your sums, correct?

CrabRevolution

https://www.boards.ie/discussion/comment/123207357#Comment_123207357

It'd be a comical waste of resources.

If I drive from the Dunkettle interchange to north of Dundalk along the M8-M7-N7-M50-M1, my maximum time saving would be under 11 minutes.

Even that assumes I maintain 130kph for the entire motorway section (m50 aside) without once encountering any road works, traffic jams, slow moving cars in both lanes, crashes, HGVs overtaking etc. Having to slow down and speed up for the 3 toll plazas will cut further into my time savings.

It would cost millions in materials and man hours to replace every single speed limit sign, plus as you say the admin and advertising of it. All to produce a slim chance of less than ten minutes in time savings for the miniscule number of people who need to regularly cover vast tracts of motorway in one journey.