They were likely from speed cameras and came through the mail all at the same time.

Tolerances for some fixed cameras (don't know about mobile cameras) in Victoria, Australia, are as low as 2km/hr (1.24 miles/hr). Which is pretty scummy given the following: Australian Design Rule 18 sets out the accuracy standards for vehicle speedos. Until July 2006 this rule specified an accuracy of +/- 10 percent of the vehicle’s true speed when the vehicle was travelling above 40km/h. That is, at a true vehicle speed of 100km/h the speedo could indicate between 90km/h and 110km/h. An odometer accuracy of +/- 4 percent was also a requirement. From July 1 2006 a new standard began its phase in and by 1 July 2007 all new vehicles had to comply. The new standard requires that: The speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h. Odometer accuracy is no longer defined. ---------- So Victoria is essentially enforcing the new design standards even on older car for which those standards did not apply when they were made. And it is for this scumbag reason that whenever I buy a new car I compare the speedo to both the speedo GPS apps on my phone read, and what my handheld GPS says. My current car reads 10% above the true speed (so if my speedo reads 110km/hr I am actually doing 100km/hr).

Using your phone while driving?

Waze is a GPS app, similar to Google maps (so it's on your dashboard before you're driving, or someone else is holding your phone) and it also tells you if you're going over the speed limit, if there are cameras/police/accident(s) reported in the area. Some other GPS systems also track the speed you're driving at, so it doesn't have to be on your phone.