The problem of this calculus you mention wasnt the speed at the end, nor even the beginning. we're missing a piece of information to properly go through this. distance. it says at a stop light, he was 0, then the next ping was 45. but the problem becomes distance covered in that 30 seconds. tie in the math, etc. if it says 45 on the ping, thats worthless. we need to know how far he traveled in 35 seconds to get an average speed, and, for the sake of argument, his vehicles 0-60 speed as well to get the stats on how quickly he could have possibly gone up to 60, nearly where they "clocked" him. obviously, his average speeds worthless, and his speed 30 seconds after his initial of 0 is worthless. we need the distance traveled in that 30 seconds. And TFA says "virtually" the same location. For all we know, he spotted the cop, hit his brakes and was doing 45 when he was pinged.
Distance is key ... notice how TFA forgets that wonderful detail.
And, I'm sure as a teenager, with a GPS, he knew that if he hit 70, theyd get an email alert. Heck, he probably knew that if he wanted to, he could go 69, wait for a ping, if he had timed them right, speed up to 100 and brake to 69 again, all before the second ping... I guess the parents forgot that Teenager + Technology is generally > Parents + technology