normally you can drive limit + 15 miles (-1), which means 79 mph at 65 speed limit, or 69 mph at 55 speed limit, but be careful when the interstate highway crosses some small towns, the traffic ticket fines are one of the primary revenue for these towns.
2. For local double yellow line road, you can drive around 5 to 10 + speed limit.
3. For community road, you better stick with the speed limit, especially around school area or small town. ( normally 25 Mph)
4. recommend to use waze to find the checkpoint to avoid traffic tickets.