A vehicle detector with improved reference tracking routines in both the Call direction and the No Call direction. Call direction tracking includes rate sensitive tracking in which the reference is only changed in response to small fluctuations in loop frequency due to drift, and one or more fixed decrementing tracking intervals during which the reference is decremented at a fixed rate for a maximum predetermined period of time. Call direction tracking also includes infinite tracking during which the reference is decremented to an end value representative of loop inductance prior to the generation of a call signal. No Call tracking permits reference updating only after the loop frequency has stabilized for a minimum period of time, a minimum number of loop frequency samples or both.