Methods of estimating vehicle location in a roadway using an automatic vehicle identification system are described. The methods involve receiving a set of response signals from a vehicle-mounted transponder at points in time and determining a range rate of the transponder relative to the antenna at each point in time; identifying a minima in the magnitude of the range rate; estimating a first position of the transponder at a first time corresponding to the occurrence of the minima; estimating a velocity of the vehicle based upon one or more of the determined range rates; and estimating a second position of the transponder based upon the first position and the velocity.