Satnav speed question!

[gasmansteve]

Hi folks
Just been given a satnav (Dayton - no I hadn`t heard of it either) for our works vans and driving along speedo says I`m doing 30mph sat nav says 25mph which is likely to be correct?. Don`t know if this explains why I inadvertantly went through a speed camera recently at what I thought was 35mph and never got a ticket or maybe I was just lucky.
cheers
Steve

 

[Digit]

The sat nav should be a clear winner, in theory.

Roy.

 

[wizer]

yes I would normally tend to trust the Sat Nav. But as you say this is a prety unknown brand. How old is your Van?

 

[PowerTool]

Under Construction and Use regulations,speedometers need to be accurate to plus or minus 10% - so if it says 30mph,you could be doing anywhere between 27 and 33.

Andrew

 

[Chris Knight]

According to Hansard..

"Speedometer Accuracy

Lord Allen of Abbeydale asked Her Majesty's Government:

Whether, in the light of the increasing importance of speed limits, they have any plans to make it easier for the private motorist to have his speedometer tested for accuracy.[HL839]

Lord Whitty: The Road Vehicles (Construction and Use) Regulations 1986, as amended, allows the use of speedometers that meet the requirements of EC Community Directive 75/443(97/39) or ECE Regulation 39. Both the EC Directive and the ECE Regulation lay down accuracy requirements to be applied at the time of vehicle approval for speedometers. These requirements are that the indicated speed must not be more than 10 per cent of the true speed plus 4 km/h. In production, however, a slightly different tolerance of 5 per cent plus 10 km/h is applied. The requirements are also that the indicated speed must never be less than the true speed.

A vehicle meeting these requirements would not be able to travel at a greater speed than that shown on the speedometer and a driver could not, therefore, inadvertently exceed speed restrictions. Her Majesty's Government have no plans to introduce instrument tests."

 

[Roger]

Actually, under Vehicle Con. & Use Regs. for the U.K. a speedometer must be accurate within the range of -0 to +10%. The EC requirements actually give drivers more leeway for the newer vehicles

It must never under-indicate for just this reason (as a defense) but may over-indicate as stated. This accuracy would be too costly for most car makers, so the vast majority of speedometers tend to over-indicate these days. baring outside influences such as bigger tires etc.

 

[ike]

Sat Navs are pretty accurate. At steady speed, continuous reception - better than ±0.5 mph.

 

[Woody Alan]

My car is fairly accurate reads about 1-2 miles an hour over the range, and my current vauxhall combo is about 4-5 miles high.
Previously I had a Ford connect transit and that was 9-10 miles high, I always drove on the gps speed on dual carriageways and had an indicated 80 and never had a problem. All the firms connects were the same.

Alan

 

[gasmansteve]

Hi all
Interesting replies, it seems that 10% seems to be the margin of error.
My van is a `Y` reg Ford transit, actually the oldest in the fleet here at York and I have been wondering about the speedo accuracy for some time but its due for renewal soon (one of the oovavoo or whatever the hell they are called :wink: ). Will have to see what collegues in the newer vans reckon.
Cheers
Steve

 

[andycktm]

Everybody i know with sat nav say that their car speedo is about 5 mph fast.
After all if the car speedo was 10% slow and you got busted for 33mph in a 30 who's fault is it?.
Or even 77 on the motorway!

 

[gasmansteve]

If 10% is the allowed tolerance then would you get busted doing 33 in a 30 zone??. Don`t know if/how that works in those zero tolerance areas like North Wales?.
regards
Steve

 

[Digit]

Neither do I. Most of us stay well away from that pillock!

Roy.

 

[gasmansteve]

Point taken Roy but in staying away from him has that achieved what he wanted in the first place?I don`t know how or why we let these people get away with whatever they throw at us but we just grit our teeth and grin and bear it me included !!.
Cheers
Steve

 

[Digit]

Time to change the leaders of the mad house I think.

Roy.