When observing another vehicle merging onto the interstate, what is the safest action?

Moving to the left lane to allow safe entry for a merging vehicle is the safest action because it creates a clear space for the other driver to merge without the risk of a collision. This action demonstrates defensive driving and consideration for other road users by providing a buffer zone. It encourages a smooth traffic flow and shows that you are aware of your surroundings.

Accelerating to pass the merging vehicle may increase the risk of an accident, as it does not account for the merging vehicle's speed or trajectory. Honking your horn might startle the driver and create further confusion instead of helping them. Maintaining your speed in the right lane might leave insufficient space for the merging vehicle, which could lead to a dangerous situation. Therefore, moving to the left lane is the best choice to facilitate a safe merging process.