Need Help - Long Exposure Shots

[RgrDat]

I shot the following long exposure shot the other night using only a 2 sec shutter speed setting. I was just messing around, but there was too much light at the intersection (which is where I wanted to get the shot as there were more moving cars). Can anyone tell me if, and if so which, ND filters I can use to possibly mitigate the crazy amount of light? Also, I know the mavic goes up to 8" shutter, has anyone been able to get any good shots with this long exposure? Is there a happy medium that allows for the best shots? Maybe one that's more forgiving while still producing some really cool shots? Any help is greatly appreciated...