If you've recently kept up with either the automotive world, the Guiness World Records, or both, you might know that the title of "fastest production car" was famously held by the Bugatti Veyron. You may or may not know that an American company, SSC (Shelby SuperCars), beat the Veyron's record by a little bit, although the SSC team believes the Ultimate Aero has the capacity to go faster.
The record run for the Aero was done on a 2 ½-mile road; having a longer road would probably make a difference. Regardless, the latest iteration of the Bugatti Veyron, the Veyron SuperSport, recently surpassed both the previous Veyron's record and that of the Ultimate Aero, so it now holds the world record for highest top speed for a street-legal car. Some people like to say the Barabus TKR is the world's fastest road car, but as none of its claims have been verified, that's just speculation.
However, the title quite likely might soon return to America, as an insanely powerful supercar called the Dagger GT. Its 9.4 liter engine produces 2000 (yes, that's two thousand) horsepower and 2000 ft-lbs. of torque on racing fuel, giving it an estimated power-to-weight ration of about 1.5:1. By the way, I do like the way it looks better than the Ultimate Aero.
Here are some of the calculated performance numbers for the car:(using wind tunnel, etc.)
0-60: Under 1.5 seconds (calculated)
Top speed: 314 mph (calculated)
¼-mile: 6.6 seconds (calculated)
Here's the car's website: