An improved fatigue cracking model is presented for jointed plain concrete pavements (JPCP) incorporated in PaveSpec 3.0. PaveSpec 3.0 is the latest version of the software developed under the FHWA project on performance-related specifications (PAS) for concrete pavements. The ability to accurately predict pavement distresses is important for successful implementation of PRS. The development process for the JPCP fatigue cracking model is described and the final model is presented along with the procedure used to calculate fatigue damage. The new JPCP cracking model has reasonable statistics for being calibrated with such a large number of data points (815) and is deemed suitable for use with the current PRS procedure. Specific improvements to the new model include direct consideration of the characteristics of the base layer, direct consideration of the effects of a tied portland cement concrete shoulder, incorporation of improved procedures for computing load and thermal curling stresses, incorporation of the influence of built-in construction curling on slab cracking, and recalibration of the model by using a database that is much improved in both quality and quantity.