production van speedo or tom tom ,which will show a more accurate speed
cheers
richard

Tomtom, speedo will overread by up to 8%.

Tom Tom

Tom Tom if on a good strait A road or above.

regards

agriv8

if the sat nav was spot on you could use it as a guidance system so i would say it can never be 100% guys

i'd say sat nav... but remember sat nav can locate you within something like 10m, so i guess for calculating speed, it could be out by whatever time it takes you to travel 20m

PLus if your on a hill then sat nav can be way out!

drive at a steady speed on a straight, flat road with no trees.. further you travel, the more accurately your tom tom will read.. my vivaro reads spot on at sixty.. speedo reads 72 mph at 70 and 85 at 80 mph... (gosh.. did I say that outloud).. keith