Coping with a zero tolerance roadscape

What does it mean now road police have scrapped any good will in respect to speed limits?

NO more leniency, so a lot more speed obsession?

Road police have scrapped their speed buffer on roads in favour of a no tolerance approach.

All motorists edging over the limit at any time of the year can now expect to be pulled over and possibly fined, national road policing manager Acting Superintendent Gini Welch has told a national media outlet.

It brings an end to a long-standing convention that law enforcement would let minor speeding breaches slide. 

“We don’t have a threshold,” Welch is reported as saying. “We don’t have anything other than the speed limit. That’s what we will enforce.” 

In theory, this raises the potential of punishment for straying just 1kmh over a posted limit. In probability?

Speed measuring tech used by enforcement agencies undoubtedly has capability of clocking just that difference, yet will police be that draconian for all motorists in all circumstances? It’s one thing to ping an individual vehicle but quite another to constrain an Auckland’s traffic stream in its entirety, right?

That’s not to say a driver shouldn’t try to stay on the right side of the law. We all need to be proactive about safe driving; anyone out there actively being stupid and presenting a danger to others deserves to be brought into line.

At same token, you’d have to imagine having to become to so zealous about keeping exactly to, or under, a posted limited isn’t good for anyone, either. It’s easy to imagine some drivers becoming focused on this to the point of distraction. How’s that a plus for road safety?

So, some good news about that. Even if you’ve been in the habit of driving j-u-u-u-s-t above the posted limited, chances are you’ve really still been in the safe zone. That’s because your vehicle has very probably always been intentionally fibbing about how fast it’s been going all.

Indeed: Here’s a statement that will generally be true - if your speedo is exactly indicating 100kmh your true speed is more likely to be somewhere closer to 96kmh. It might even be slower.

Sorry, you’re telling my car’s speedo is inaccurate?

Yup.

Speedometers are always calibrated to over-estimate a vehicle's true speed to help stop drivers from unintentionally speeding.

The actual allowance for margins of error varies between car makers and models and is not disclosed, but as a rule they have always set speed measuring devices to read faster than actual road speed.

Why are they doing this? 

It’s a safety net.

International regulations in respect to speedometers is reasonably uniform.

Industry standard is that a speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4kmh.

Accordingly, manufacturers target a suitably high overestimation - in the five to eight kays an hour range - and that allows them some wriggle room on intrinsic speedo accuracy and differences in tyre sizes and so on. I’ll have more about the latter in a minute.

Isn’t this a bit duplicitous?

Well, I suppose it’s something you could argue out in court – but why would you?

 Makers could argue they’re being proactive and argue this is a safety net that’s good for all. Hands up those drivers who might occasionally sneak over the legal speed limit without realising it? Yup, exactly.

And that’s the only reason they do it?

Well, okay, it also means you really cannot blame the manufacturer for committing a speeding offence - because the speedo didn’t make you do it. In fact the speedo is probably slowing you down.

And you’re saying this is a status quo?

Yup.

And it’s been shown to be true in testing. For instance, a couple of years ago a big media outlet in Australia undertook an exhaustive test, spanning five months and involving 60 popular models new at the time. 

It found 93 percent inaccuracy and showed most speedos measured over the posted limit by an average of 5kmh at 100kmh – well within the Australian Design Rule parameters which align with European regs in requiring a vehicle's true speed must not be higher than the speed indicated by the speedometer. 

The most inaccurate reading was from a large heavy duty off-roader no longer being sold in New Zealand (though it was then). It was out by 11kmh. Just as a matter of interest, luxury cars fared better in the testing than regular passenger cars – usually within 2kmh of the true speed – as did models built in Australia. The compulsion to achieve greater accuracy with the latter increased when some states, notably Victoria, cut out leniency some years ago. And Victoria, of course, has long been the one state that NZ authorities seem to see as the leader they must follow for road safety practice.

And you’re saying this is ALWAYS the case?

Well, almost always. One crucial factor it assumes is that vehicle has not been modified inappropriately in terms of wheel/tyre size.

It’s not uncommon for a manufacturer to issue a product with a wide range of wheel and tyre sizes; but even when they do this, care is being taken not to change the overall rolling radius and total wheel height of the wheel/tyre set. 

So, for instance, a base model on 16-inch rims and a flagship on, say, 19s will still have the same rolling radius, as the smaller wheel will carry a taller tyre whereas the larger will be fitted with lower-profile rubber. 

It’s when people move to nicer rims and different tyre choices beyond the maker’s spectrum where things get interesting. If you manage to reduce the total wheel height, then the speedo will show a faster speed than the vehicle is actually going. On the other side of the spectrum, when bigger tyres are fitted, the opposite effect on the speedometer occurs.This particularly happens with off-road models when they are fitted with either mega-sized dirt tyres or, alternately, with larger rims than the maker will provision as original equipment.

So, okay, we ‘ve taken all this on board and have decided we want to be absolutely certain we’re not exceeding the limit, even by a fraction. Is this possible? 

I know where you are heading with this: GPS.

Global positioning satellite tech is a fantastically useful to establish location and ground speed. That’s why these have become a fairly common and handy accessory and driver aid in recent years. 

That speedo accuracy check in Australia was undertaken using a satellite phone app. Sitting on 100kmh with the cruise control activated, testers monitored the true speed of the app over a period of about 60 seconds, comparing it with a vehicle’s indicated speed. The app reading was then compared to an industry-certified GPS performance meter, to ensure absolute accuracy.

The results were considered bombproof, but testers were very specific about something else: The trial zone. All tests were conducted on the same flat stretch of road.

That’s because GPS accuracy is potentially compromised uphill or downhill. The system itself is reasonably robust for the Z-coordinate, but the receiver you use might not be paying that much attention to elevation in practise.

So you’re not advocating GPS as an absolute?

Well, let’s just say it might shoot you in the foot. For sure, if you want to drive legally, but at the maximum permitted speed, you can suck a GPS unit to your windscreen and compare it reading to that of the speedo to derive a correction factor.

But be aware error might not be constant across all operating speeds in your car. Also, GPS systems that indicate a vehicle's speed have NO built-in safety margin.

Plus, consider the degree of focus it will require. Even for the most fanatical and focused driver, trying to consistently drive to the maximum speed limit even for the shortest distance is pretty much impossible.

 There’s argument that the risk of getting caught speeding increases if drivers travel to the speed indicated on the GPS system, and ignore the vehicle's indicated speed.

And by the way, when discussing GPS, we’re talking about external devices, not the integrated system that the car maker has primarily provided to provision sat nav duty. The latter generally do not display speed. Presumably because manufacturers don’t want to open the floodgate of complaints about speedo inaccuracy from indignant customers, when they see two mutually irreconcilable readings on the same instrument panel. 

So why not just put my absolute trust in cruise control?

That’s really only going to work on the open road and the degree of usefulness will come down to how smart your cruise control.

To explain: Cruise control oversees your car’s speed in exactly the same way you do. Via the throttle.  These days it’s a wholly electronic set-up run through a computer which attunes to when the car has reached the desired speed or when it’s falling away from that pace.

Now we’re into the era of adaptive (also called active) cruise control, which adds in either a radar or cameras to help your car use another car’s speed to regulate its own based on your own pre-set speed. 

Regardless, the big test of how smart your cruise control will come as you head down a hill.

Some systems are able to retard the vehicle in that scenario, either through self-braking the car or at least using the gearbox, if it’s an automatic, to induce some engine braking. But these are in the minority.

If your car has a cruise control that just relies on the throttle to control speed and not the brakes, you’ll need to be ready to induce some braking to prevent ‘running away’ down a hill.

As said, if you have an automatic with ‘grade logic control’ it might have better chance of maintaining the pre-set speed, as this allows the gearbox to sync with cruise control. The system will downshift the gearbox to provide more engine braking.

However, now we’re seeing some advanced cruise control systems that will apply the brakes to keep speed in check when travelling downhill. One or two even detect corners and slow down. An increasing count are now able to read speed signs and adjust the vehicle’s pace accordingly. 

And they’re not all really expensive, either. One of the very best systems in the market is Intelligent Speed Assist, which not only tells the car you don’t want it to exceed a sign-posted speed limit, but will self-slow it when, say, moving from a 50kmh zone to a 30kmh area. This fits to a budget car, the Ford Focus

Is there a chance that police speed radar readings can be wrong?

That’s a touchy subject with the rozzers but, yes, any web search on this subject will deliver a rich haul of international tales about occasions when speed measuring devices have had to be pulled and tickets rescinded because of faulty readings.

Police use mobile and fixed speed cameras, plus radar and laser speed detection devices, either hand held or mounted in a vehicle. All sorts of information about the latter can be found on the we – we even discovered an operator’s manual (dating from 2013). The accuracy and fallibilities of equipment used by New Zealand police seems to be open to question. It’s not something I’m going into here, but assuming it is still accurate, the following made some interesting points.

https://drivetribe.com/p/police-radar-Nh9xuJ51Qo-H3dqE6LNYtg?iid=JlRN-XQ0Q8m1myf4sE-5BQ 

Right, so all in all this could be a challenge for everyone – so why are they doing this?

Police are adamant. Their research overwhelmingly shows whatever causes a crash, the outcome depends on speed. Driving below the speed limit and to the conditions reduces death and trauma on our roads. They say most illegal speeding is in the one-10kmh band above the limit. Speeds in this band are associated with the most crashes.

Therefore, they argue, everyone travelling a few kilometres slower makes us all safer. With even a small decrease in average speed, we see a decrease in the number of fatal and injury crashes.