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Old 22nd August 2019, 10:20   #16
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Re: Speedometer calibration: Government says that vehicle should overstate speed

I had no idea this was the case; regardless of the intention, I'm surprised why it is so. Why should a gauge not always display the accurate reading? When laws/regulations expect facts/data to be black and white, how is this shade of grey accepted?

Would we be okay if the label on say, a soda bottle overstated the volume just because soda is not good for health?

Quote:
Originally Posted by Thermodynamics View Post
I asked him why 9, he said, 10 would be a double digit overspeeding and more likely to attract ticket
Nope; that's not why. From what I've heard/read:all instrument gauges (in law enforcement terms: speed gun, alcohol check meter) develop some error in reading over time and in the US, are required by law to be calibrated periodically. An accepted error in reading (actual vs. reading) is 10%. Hence, cops won't fine if you are just under 10% over the speed limit.

Last edited by libranof1987 : 22nd August 2019 at 10:32.
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Old 22nd August 2019, 10:24   #17
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Why does the govt have to intervene is every little thing? Someday I'd like to see a properly done survey which co-relates speed to accidents. I'm willing to bet that accidents that happen due to pure speed alone are a small percentage and most happen because of something or the other obstruction on the road, like a cow or a pedestrian or a two wheeler (in case of 4 wheeler accidents) or even a 4 wheeler suddenly changing direction/lanes.
All around the country, the municipalities/traffic police are hell bent on curtailing speeds when in reality we already have some of the slowest average traffic in the world. That distinction hasn't stopped any accident, how would any of the stop accidents is beyond me. /rant over

Quote:
Originally Posted by libranof1987 View Post
Nope; that's not why. From what I've heard/read:all instrument gauges (in law enforcement terms: speed gun, alcohol check meter) develop some error in reading over time and are required by law to be calibrated periodically. An accepted error in reading (actual vs. reading) is 10%. Hence, cops won't fine if you are just under 10% over the speed limit.

I was fined on the NH1 near Panipat once for driving at 94kmph when the speed limit there is 90. The cops only want to collect money, that's their incentive. Their incentive is not to stop speeding. That's where the whole problem lies.

Last edited by Gannu_1 : 22nd August 2019 at 10:50. Reason: Back to back posts merged. Please edit your first post and add content if re-posting within 30 mins. Thanks.
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Old 22nd August 2019, 10:44   #18
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Quote:
Originally Posted by libranof1987 View Post
An accepted error in reading (actual vs. reading) is 10%. Hence, cops won't fine if you are just under 10% over the speed limit.
Quote:
Originally Posted by Thermodynamics View Post
I asked him why 9, he said, 10 would be a double digit overspeeding and more likely to attract ticket
There is no hard and fast rule in such cases. It is totally up to the local enforcement. Like in Michigan, up to 85 mph was considered okay although posted limit is usually 70 mph. In northern Virginia, even 2 or 3 mph over the limit is considered risky. In Texas, again 85 mph was considered defacto limit regardless of posted limits. In Northern California 75-80 mph was considered okay though many highways have 65 mph limit. Its all up to the local traffic flow. Many states implemented speed limits long ago & haven't revised them. So even law enforcement considers posted limits as dated and low by today's standards.
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Old 22nd August 2019, 11:51   #19
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Quote:
Originally Posted by libranof1987 View Post
An accepted error in reading (actual vs. reading) is 10%. Hence, cops won't fine if you are just under 10% over the speed limit.
That’s not true. My FIL recently received an echallan for doing 52kmph in a 50kmph zone. My brother has been challaned for going at 91kmph when the limit was 90kmph.

The cops are least concerned about road safety and are solely interested in money. The only agenda is revenue maximisation and achieving collection target, personal as well as official.
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Old 22nd August 2019, 12:20   #20
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Re: Speedometer calibration: Government says that vehicle should overstate speed

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Originally Posted by Shreyans_Jain View Post
That’s not true. My FIL recently received an echallan for doing 52kmph in a 50kmph zone. My brother has been challaned for going at 91kmph when the limit was 90kmph.

The cops are least concerned about road safety and are solely interested in money. The only agenda is revenue maximisation and achieving collection target, personal as well as official.

Well you can't blame them for following the rules, can you? Had it been an automatic camera, it too would have penalized any speed above the limit, irrespective of it being 1kmph or 2kmph above. That said, there might be few rotten ones, but let's accept it when it is fair.

We tend to blame the officials a tad too much. Darn it if they do, darn it if they don't.
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Old 22nd August 2019, 13:13   #21
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Re: Speedometer calibration: Government says that vehicle should overstate speed

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Originally Posted by ValarMorghulis View Post
We tend to blame the officials a tad too much. Darn it if they do, darn it if they don't.

Not blaming anyone. Just providing a counter point to the 10%+ (hear say) rule most people cite. All I'm saying is there could be a measurement error also and so 1-5% should ideally be allowed and if it's allowed it should be in the law, in black and white. Right now, sure the guys are doing their duty, hopefully.
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Old 22nd August 2019, 13:32   #22
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I was doing 120 (speedo), on the Delhi Amritsar highway, and somewhere near Panipat I was flagged down for overspending, the speed gun had me doing 108 km/hr. Car: 2012 VW Polo

So yeah, VW has a + 10% error as well.
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Old 22nd August 2019, 15:05   #23
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Quote:
Originally Posted by ValarMorghulis View Post
Well you can't blame them for following the rules, can you? Had it been an automatic camera, it too would have penalized any speed above the limit, irrespective of it being 1kmph or 2kmph above. That said, there might be few rotten ones, but let's accept it when it is fair.

We tend to blame the officials a tad too much. Darn it if they do, darn it if they don't.
We don’t know what kind/quality of equipment they use. We don’t know how reliable it’s readings are, and how much role human error or equipment setting plays in the output. We don’t know how well their equipment is calibrated, how frequently it needs calibration or if it has indeed been showing error. We don’t know if readings or the reliability of readings is affected by our extreme weather conditions.
We don’t even know if it is possible to game the equipment into showing speeds say 5kmph higher than actual (like how unscrupulous petrol pumps show more fuel than what actually goes in).

If the limit is 100 and I am doing 120, yes I am at fault and deserve to be hauled up. It is beyond reasonable doubt. But when you challan me for as little as 1-2kmph, that I feel is unfair and honestly, pretty ambiguous. You cannot and should not expect the driver to drive with one eye continuously on the speedo. A std allowance of say 10% should be there to accommodate human and machine error.

Last edited by Shreyans_Jain : 22nd August 2019 at 15:08.
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Old 22nd August 2019, 16:58   #24
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Re: Speedometer calibration: Government says that vehicle should overstate speed

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Originally Posted by Senna4Ever View Post
That's a wrong interpretation. Same wrong interpretation has been made in the Team-BHP news post also.

First, indicated (speedometer) speed should always be more than or equal to the true speed. (and not necessarily by 4kph, 6kph etc..)
From the news article:
Quote:
The rules specify that the indicated speed shall exceed the true speed by more than 4 km/h, 6 km/h and 8 km/h across the various vehicle classes.
Quote:
Originally Posted by Senna4Ever View Post
Second, indicated speed should not exceed the true speed by more than (for a car): 10% of true speed + 6kph.
Please refer below screenshots for better clarity:
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Old 22nd August 2019, 18:13   #25
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Quote:
Originally Posted by blackwasp View Post
From the news article:


Somewhat OT

But as a guy who visits the forum directly, without visiting the home page, feels good to know that two of my threads(this and the ZX10R 250 kmph one) have made the front page in such a short span of time.

Immensely honoured.
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Old 22nd August 2019, 18:28   #26
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Re: Speedometer calibration: Government says that vehicle should overstate speed

As others have spoken, speedo indicated speeds are already more than true speeds. So, this regulation is nothing new.
Once, long before, I checked my Civic for the same and found that the error starts creeping at around 50 kmph and locks to exactly 5 KMPH at speeds of 100 KMPH.
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Old 22nd August 2019, 19:03   #27
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Not sure about government regulations, but all cars that I have driven so far in Indian and abroad, overstates the speed (atleast ones with analog speedometers). Is there a technical reasons to it or is it always done due to government regulations?
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Old 22nd August 2019, 19:05   #28
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Quote:
Originally Posted by blackwasp View Post
From the news article:
I hope this doesn't get OT (even though I really enjoy such discussions )
  • For the second requirement of not exceeding a limit (10%+6kph), I agree with the interpretation/text that you wrote and underlined. No confusion there..
  • For the first requirement, i will have to humbly insist that interpretation is wrong. To be specific, the ''by more than'' part of the sentence.

With the sentence: ''by more than 4 km/h, 6 km/h and 8 km/h across the various vehicle classes.'', one is supposed to understand that a minimum difference of 4/6/8 kph is required between speedometer and real speed. If this was indeed your intended message (?), then you are forgetting this:
Speedometer calibration: Government says that vehicle should overstate speed-inkedscreenshot-20190822-4.54.05-pm_li.jpg

Speedo can, in theory and legally, show the true speed or have a difference of just 1, 2 or 3 kph. Difference doesn't have to be, in your words, ''by more than 4 km/h, 6 km/h and 8 km/h"

Hope i could show the distinction.
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Old 22nd August 2019, 22:55   #29
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Re: Speedometer calibration: Government says that vehicle should overstate speed

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Originally Posted by Thermodynamics View Post
I always had doubt, now realized it could be true. This could also be true in other countries. One of my US friend says, different states have different speed limits and overspeeding tickets hurt. Given the size of US they often need to munch miles. He runs 9 mph above limit on interstates and he never got a ticket in 35 years of driving. I asked him why 9, he said, 10 would be a double digit overspeeding and more likely to attract ticket
In California, for 65Mph rated freeways, Cops usually never used to give tickets upto 80 Mph, unless there is a road work going on. Anything over 80 is an issue. So I have seen people setting their cruise control at 78 or 79.
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Old 23rd August 2019, 05:23   #30
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Re: Speedometer calibration: Government says that vehicle should overstate speed

Ever tried changing the time on your watch to a few minutes faster? The human brain sees the time, it knows it's not yet the time that the watch shows but yet, phychologically, you end up following the time that the watch shows.

You never want to have a slower time on your watch though.

It's the same case here. Err on the side of caution.
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