What is more dangerous? Driving below the speed limit or above?

Both are dangerous but in different ways. If you are driving 25 mph on a 2 lane country road you might get rear ended but if you drive 90 on a 2 lane country road you may cause a head on crash or run off the road into a ditch

As with most things - it's situational.

The general rule is to keep pace with other traffic.

You normally drive at the speed the traffic wants to flow at. Neither faster nor slower. Going at a different speed disrupts the flow and caused a dangerous condition.

Once when I was driving back to LA from Vegas the traffic near Ranch Cucamonga on the 15 was flowing at 90. Even the California Highway Patrol cars were going with the flow. Other days the traffic wants to flow at 30 and that is also what you do.

Still, slower is somewhat less dangerous than faster.

Sitting in the fast lane doing 30 ks below the limit is as bad I saw an idiot with 4 cameras on its car doing just that the other day sitting in the fast lane on the freeway 30k's under the limit How long until someone cleans him up I wonder

Driving above the speed limit, always. The faster you drive, the damage caused by a collision rises exponentially, and the less control you have over the vehicle.

Driving below the speed limit under ideal road conditions is less safe on multi-lane highways because it interrupts the traffic flow. But more accidents are caused from driver frustration and taking foolish risks to get around 'the slowpoke', and that is 100% preventable. It's your job to identify hazards ahead of time and manage them.

On Interstates and multi-lane (one direction) roads, below the speed of traffic and above the speed of traffic- are equally dangerous, regardless of the posted speed limit. On single lane roads (in one direction) going over is more dangerous.

In more scenarios above the speed limit, because it adds the danger of you not being completely in control of your vehicle. Especially if you re driving a 370z or something drifty.

Above the speed limit.