You should be leaving enough stopping distance between yourself and the next car that someone can merge easily and you have time to react by slowing down or moving to the next lane to make space for them. If you don’t have that much stopping distance, then you’re already in danger if the car in front brakes suddenly, e.g. if they need to do an emergency stop because of something you’ve not seen, they have a medical event making them lose consciousness and accidentally step on the brake pedal, or their car breaks down in a way that forces the breaks on.
It really doesn’t have anything to do if there is a car in front or not.
At least in the Pittsburgh area, because of the hilly terrain, there is often not enough reaction time between seeing if a car is waiting on an on ramp and switching lanes.
You should be leaving enough stopping distance between yourself and the next car that someone can merge easily and you have time to react by slowing down or moving to the next lane to make space for them. If you don’t have that much stopping distance, then you’re already in danger if the car in front brakes suddenly, e.g. if they need to do an emergency stop because of something you’ve not seen, they have a medical event making them lose consciousness and accidentally step on the brake pedal, or their car breaks down in a way that forces the breaks on.
It really doesn’t have anything to do if there is a car in front or not.
At least in the Pittsburgh area, because of the hilly terrain, there is often not enough reaction time between seeing if a car is waiting on an on ramp and switching lanes.