On the subject of driving

[Steve Walker]

In most modern cars, the black box has access to wheel speed sensors in all four hubs (these are required by the antilock braking system) - alternatively, it may take an input from a sensor in the gearbox.

 

What is interesting is that while all cars report their speed inexactly (because any estimation of road speed from how fast the wheels are going round must make an assumption about tyre diameter, which will depend how much tread is left on them) some cars then proceed to lie about how fast they think you are going. Someone in the owners club for my old car plugged a scanner into his car to interrogate the ECU and record data - he noticed that the speed reported by directly interrogating the ECU was consistently lower than the speed shown on the digital speedo. It is a requirement for type approval that speedometers never under-read, so that's how they were covering their arses!

Edited July 20, 2012 by Steve Walker

[captain cojones]

I never bother using the speed reader of the car.

Just use the GPS instead its more accurate.

[Steve Walker]

I never bother using the speed reader of the car.

Just use the GPS instead its more accurate.

 

On the motorway, I tend to set the cruise control to a cop-safe speed based on the GPS.

[crumpercatcher]

Lowering the speed limits on these roads has very little to do with road safety. National speed limit / 60 / 50mph roads must be maintained by local authorities to a higher standard than a 30 mph or 40 mph road. It is all about cutting corners and saving money, not road safety.

[captain cojones]

On the motorway, I tend to set the cruise control to a cop-safe speed based on the GPS.

 

same here.