Drive V is the result of 5 years and over 2,000 hours of learning the physics system and testing in order to create a realistic and fun experience. Every vehicle is unique (even some variants that originally shared the same handling line) and has had careful attention to every single dynamic attribute. The most critical change I felt was needed was the Z-axis rotation, which is what made the vanilla cars feel so darty with every flick of the wheel. Now, heavy and old vehicles have a realistic delay between steering inputs and the car reacting, giving something like the Emperor the sloppy feel of a '70s Cadillac, and making semi trucks actually feel like you're driving a massive rig. You'll also notice vehicles like the Emperor have a very soft suspension and more body roll (but not cartoonish GTAIV levels of roll). For an example of the attention to detail: The taxi has less precise steering and poorer brakes than the police variant to reflect wear and tear because taxis are often driven hard with high mileage. The police variant gets a power boost and improved handling to reflect the police package upgrades, but still feels like a heavy Crown Victoria that's prone to oversteer, whereas the Interceptor drives like a more modern car.
Power levels and acceleration have been adjusted to match vehicles' real world counterparts, to the extent of calculating the net SAE horsepower ratings of old muscle cars that used a different rating standard (SAE gross) to determine a true realistic power output. Off-road traction has been overhauled for realism. Damage/deformation has been increased to a realistic level, similar to GTAIV. Downforce has been removed from everything except supercars that would actually produce downforce. Finally, the original game had many cars sitting at unusually low ride heights, so they have been raised to reflect the ride heights of their real world counterparts.