As far as production cars go the McClaren F1 has the highest top speed.
The highest speed limits on public highways can be found on the German Autobahn, where some sections have no speed limit. However, there are also race tracks like the Nürburgring Nordschleife in Germany where cars can reach even higher speeds.
what is the maximum speed limit in florida
A GATSO speed camera
As fast as other cars get out of the way
8 mph in CT
50 mph
A realistic speed limit depends on the circumstances, the vehicle, the conditions and the ability of the person in charge. A speed limit suitable for race cars would not be suitable for urban areas.
80 MPH
70 mph
There are two ways cars could be made so they couldn't go any faster than the highest speed limit: 1. The car could be made so that the maximum speed limit was the absolute highest speed the car was capable of. But any machine, when you push it to its absolute limits, is likely behave unpredictably and break down, so this would be rather dangerous. 2. Governments could force car manufacturers to install devices which artificially limit the speed the of the car. Actually I think this might already be done with some buses and trucks/lorries (certainly some are fitted with devices which record the speed). But applying this to personal cars is generally considered too intrusive and politically difficult, and I'm not sure how easy it would be to make them impossible to remove.
we have a limit of 75 in some states and no speed limit in some states out west