I hope that most drivers subscribe to the Two Second Rule under good driving conditions and increase the following distance when the situation is not ideal. It certainly makes sense to leave sufficient room between your vehicle and the one you are following to create a safety margin. Why then do some drivers make lane changes that force the driver behind them into being a tailgater?
When I was being taught to drive the instructor said that I was not to make a lane change until I could see all of the front of the vehicle behind me in my center rearview mirror. This would insure that there was a safe distance between us when I did move over in front of the other driver. Unfortunately, it appears that this has been forgotten or is not being taught to drivers today.
All too often I am cruising in the right lane at the speed limit when I am overtaken by another driver who may or may not signal before jamming their vehicle in front of me about 2 vehicle lengths away. Now I have to drop back to maintain my space cushion and this becomes especially difficult if the driver behind is tailgating me.
A driver must not drive from one lane to another unless the driver has ascertained that movement can be made with safety and will in no way affect the travel of another vehicle. This requirement is straight forward, if I have to slow to maintain safe following distance after you change lanes in front of me, you are in violation. Remember that half the driving world is in your rearview mirror and deserves as much of your consideration as the half that is in front of your windshield.
Lane Change Must Not Affect Other Traffic - Section 151(a) MVA