This paper presents a tool for the evaluation of employer-based transportation demand management (TDM) strategies. The conventional method of evaluating TDM strategies has typically been to conduct expensive before-and-after strategy implementation surveys. As an alternative approach, this research uses a joint revealed preference (RP) and stated preference (SP) survey (the RP–SP survey) administered before deployment of the TDM strategy, which is more cost-effective and efficient. The data collected from the RP–SP survey were used to estimate an advanced discrete choice model, which was packaged into a spreadsheet-based tool for TDM decision support. The tool adopted the concept of penetration rate, whereby only a subset of the target population could be targeted for any specific TDM strategy. The tool that was developed provides an alternative approach for the predeployment evaluation of any TDM strategy for efficient implementation. Moreover, the empirical model used in the tool reveals many behavioral details about commuters’ responses to employer-based TDM strategies.