Can you explain how the speed limit display works?

[GURU4U2BUY]

Many people have different ideas about how cars determine the speed limit: through cameras or GPS? This week, TFL fixed the problem for my EV3 by lowering the limit from 40 to 30, all it took was removing a few 40 signs from the exit of the 30 zone. The dash display in my automobile always changes to 40 at the aforesaid position, even though it normally changes at the threshold of each restriction. It must be the GPS mapping since there are no longer forty signs.

[Edmonston33]

Mostly it's GPS, but signs take precedence. Thus, it may occasionally inform you that the limit has been reduced to 20, for instance, in a 30, due to a misreading of the sign for a side turn.

There is a section of the A6 in the area where the limit was recently reduced from 40 to 30. Presumably due to unupdated mapping, it initially recognises the 30 sign then reverts to the 40 sign approximately halfway through.

[killiomop]

agrees that signs take precedence over GPS readings for determining actual speed. In order to compare it with the EV3 speedo, I purchased an additional GPS speedometer for use on a boat. Around every corner, they were in complete agreement. Because of this, I am quite cautious when attempting to maintain a speed of 10% below the posted limit!

[GURU4U2BUY]

Rather than measuring the vehicle's real speed, the idea was that GPS mapping data included information about local speed limits. I might end up tumbling over the Hindhead tunnel in my speedo if it happened!

[Noble4u]

We purchased our EV3 in Spain. The speed restriction is often inaccurate. The speed limit is 40 kmph on larger routes and 30 kpmh on smaller ones. Due to my back pain, we frequently take a tarmacadamed, one-way side road that runs parallel to the main road (40 kph, marked with metal speed bumps). "Normally," one shouldn't go faster than 30 kph, because there are many pedestrians, bikers, dog walkers, runners, etc. According to our EV3, the speed limit is 90 kmph! If the authorities pulled you over for speeding, would you be able to use the data from your vehicle as evidence?

[GURU4U2BUY]

The speed limits in Spain that do not apply to motorways are 90, 60, 30 and 20 kph, which is quite similar to the UK's 60, 40 and 30/20mph limit. Maybe rural Spain's GPS mapping is lacking in development, with 90 kph being the default?
I don't see how the car's displayed limit could ever be used as a defence in court; after all, everyone knows the technology isn't perfect. Who among us has the guts to sue a manufacturer over a traffic violation?

[Noble4u]

Much obliged, but I seriously doubt we'd have a chance against the authorities or the manufacturer. Even though it looks like it's in rural Spain, the street actually lies in a metropolitan suburb! That's the strangest part! Not sure if it's worth it to update the maps (I assume it would cost money to do so). would have any impact on this!)

[lumperjack]

Manufacturers cannot be sued. Because it is the duty of every driver to observe traffic laws and regulations. The same goes for making sure the vehicle is roadworthy.

Are you going to follow the directions on the satellite map over a cliff without thinking?


These systems rely on accurate data, which is often a result of local governments informing mapping companies of changes (there were three distinct reporting systems in the UK as of last count). Councils that are short on funds will find this to be a simple way to minimise costs.
This may not be as big of a problem with the new ccNC since it receives more updates (like phone apps), unlike the previous two versions, which were frequently outdated when consumers received them.