First, the unsafe lane change is something that clearly no radar is needed for, and once an officer sees you do that, he can pull you over and then cite you for no seatbelt. So it would seem that you probably do not have grounds to fight those, unless you feel the officer is lying AND feel you will  be more believable, persuasive, reliable as a witness, etc. than him.Similarly, the law does not require that an officer use a radar gun. He can testify as to what your speed was and why he believes that and the issue will be how believable he is--and how believeble any testimony of yours to the contrary is. For example: officer says, "I was going 55 mph. The defendant passed me, and based on 12 years experience as a patrolman, I estimate that he was goiing 15 mph faster than me"--that's very reasonable and believable testimony. If instead he says, "I saw defendant in the distance doing at least 100mph down the exit ramp," that's much less believable because of distance and  because it may be impossible to go that fast down that ramp (depending on its slope, curve, length) without crashing.