driving slow : your views ?

bod1467

We have a 30 mph speed warning sign on a road in our town. If I go past it at 35 (with cruise control set) it indicates; if I go past at 33 it doesn't.

Comparing indicated speed against satnavs (I've tried 2 different devices and they both seem to match) I get the following ratio (approx):

Speedo Satnav
75.........70
64.........60
54.........50
43.........40
32.........30

Meaning my speedo reads about 7% higher than actual travelling speed.

bod1467

Regarding digital speedos ... these count pulses against a reference time source. If the detector head starts to fail (and miss pulses) then the accuracy will go. If the time source starts to slip then accuracy will go.

So whilst digital speedos (in terms of the measurement technique, not necessarily how it is displayed) tend to be more accurate and stable than analogue units, they don't remain with a fixed accuracy indefinitely.

nobbysn*ts

dori2o wrote: »

Probably because they are not travelling at the speeds being displayed by the speedo, AND because most local authorities apply tolerances to the speed limits because of the fact that speedos are not accurate.

For example, our LA has the cameras set at speed limit + 10% + 4mph, so in a 30 zome the camera's, fixed and mobile, are set at 30 + 3 + 4 = 37mph.

Looking at other LA's in this area they seem to apply the same rules.

Therefore people travelling 33-36mph are not committing an offence.

Yes they are. They're just not being caught.

nobbysn*ts

bod1467 wrote: »

Regarding digital speedos ... these count pulses against a reference time source. If the detector head starts to fail (and miss pulses) then the accuracy will go. If the time source starts to slip then accuracy will go.

So whilst digital speedos (in terms of the measurement technique, not necessarily how it is displayed) tend to be more accurate and stable than analogue units, they don't remain with a fixed accuracy indefinitely.

If the head goes, it throws up a fault that the ecu logs when it sees random or rregular pulses. If the ecu clock frequency slips, the ecu will error. Usually fatally.

Cornucopia

nobbysn*ts wrote: »

Me? I believe in inertia....

I think you may mean momentum?

Anyway, that sounds like an argument for widespread reduction in speed (limits), and in particular much lower limits for heavier vehicles.

In reality, motorways are the safest roads. In contrast, speeders on local/residential roads can make life hell for people, and increase the chances of pedestrian injury considerably.

nobbysn*ts

Cornucopia wrote: »

I think you may mean momentum?

Anyway, that sounds like an argument for widespread reduction in speed (limits), and in particular much lower limits for heavier vehicles.

In reality, motorways are the safest roads. In contrast, speeders on local/residential roads can make life hell for people, and increase the chances of pedestrian injury considerably.

Nope. Inertia. Newton's Laws of Motion. In reality motorways may be safer to the mind of the speeder, until one person messes up at 80mph , then they're a lot unsafer than one person messing up at 26mph

jase1

nobbysn*ts wrote: »

Maybe because they see what happens at 80mph, and what happens at 26mph?

Children will not be crossing motorways though; they frequently do cross roads in built-up areas.

40 in a 30 is the equivalent of 80 in a 60, or 93mph on a motorway. I somehow doubt though that the 40mph monospeeders would see their actions as equivalent to doing 90+ on the motorway.

Speeding in built-up areas is just about the most dangerous form of speeding there is, and those who career around town at 40, or even 45-50mph need to be strung up by their genitalia IMO.

nobbysn*ts

jase1 wrote: »

Children will not be crossing motorways though; they frequently do cross roads in built-up areas.

40 in a 30 is the equivalent of 80 in a 60, or 93mph on a motorway. I somehow doubt though that the 40mph monospeeders would see their actions as equivalent to doing 90+ on the motorway.

Speeding in built-up areas is just about the most dangerous form of speeding there is, and those who career around town at 40, or even 45-50mph need to be strung up by their genitalia IMO.

Even when it's a perfectly clear road, in the early morning, in good dry weather? And for 40mph? That's only 3mph over the 'real' limit. "For example, our LA has the cameras set at speed limit + 10% + 4mph, so in a 30 zome the camera's, fixed and mobile, are set at 30 + 3 + 4 = 37mph." Bit harsh for the extra 3 mph from the 37."

bod1467

Yes. Mono-speed-morons are as bad as middle-lane-morons (if not worse). I accept that 35 in a 30 might happen quite easily, but to do 40+ in a 30 is irresponsible, regardless of the conditions or time of day.

jase1

nobbysn*ts wrote: »

Even when it's a perfectly clear road, in the early morning, in good dry weather? And for 40mph? That's only 3mph over the 'real' limit. "For example, our LA has the cameras set at speed limit + 10% + 4mph, so in a 30 zome the camera's, fixed and mobile, are set at 30 + 3 + 4 = 37mph." Bit harsh for the extra 3 mph from the 37."

40 in a 30 is 33% over the legal limit. That is utterly unacceptable.

It really grinds my gears when I hear people who do 40 in a 30, complain about speeders on motorways, when what they are doing is far worse.

You shouldn't be looking at speeding in terms of number of mph over the posted limit -- it's percentages that matter.