Description updated for V1.4:
I. Installation
extract DRV.cs to 'cleo' folder
extract DRV.fxt to 'cleo_text' folder

II. Controls
G - enter as passenger to any vehicle
Z - activate/deactivate autopilot (stop car)
X - Follow Marked Coordinate

III. How it works
1. When activated, the mod would generate a Mafia ped if the driver seat is empty. Once the player goes out of the car the Mafia ped would be automatically deleted.
2. If there are other peds in the driver seat or if CJ is in the driver seat, the mod wouldn't generate a Mafia ped. The ped wouldn't be deleted when CJ leaves the car.
3. This doesn't work on planes and helicopters.
4. Cars you used would end up being "all-proofed" and I didn't bother remove the specialties. It's all good.
5. A separate driveby mod is available. See posted links.

The driveby mod as promised; click here
Toggle Car Immunities; click here
Parked Vehicles; click here

NOTE:
In cases of cars you hopped in with drivers, the ped continues to follow the traffic normally when the autopilot is deactivated. To stop the car, activate the autopilot again and exit the vehicle or activate the autopilot then deactivate.

As of version 1.4, you can now leave the car to deactivate the autopilot. Glitches that occur when used with the driveby mod (cars being unlocked and driveby being deactivated) are now fixed.

Be sure to download the latest versions and update all files.