1. A method comprising: receiving a plurality of images of a vehicle passing over a surface of a roadway from at least one camera module of a license plate recognition imaging system, wherein the surface of the roadway is within a field of view of an image sensor of the at least one camera module; determining an estimate of speed of the vehicle passing over the roadway based at least in part on a difference between a first pixel location of a portion of the vehicle in a first of the plurality of images and a second pixel location of the portion of the vehicle in a second of the plurality of images, wherein the determining the estimate of speed of the vehicle involves a correction to the difference between the first pixel location and the second pixel location based on a plurality of passes of a vehicle through the field of view of the image sensor, each pass of the vehicle at a constant, known speed; and storing the estimate of speed of the vehicle in a memory.