Traffic signal operators are often faced with the challenge of assessing the performance of signal operation and troubleshooting day-to-day operational issues. In many cases, the problems can be specific to a certain time of day or exclusive traffic patterns; this specificity makes it more difficult to pinpoint the problems without spending hours or even days at the sites. With limited resources and budget constraints, public agencies need to find a more efficient and cost-effective approach to operating and maintaining an ever-increasing number of signals within their jurisdictions. To address this challenge, the authors developed a portable tool that consists of a field-hardened computer that interfaces with the traffic signal cabinet through special enhanced bus interface units. The toolbox consists of a monitoring tool and an analysis tool. The monitoring tool monitors and logs relevant events within the cabinet that provide input for analyzing intersection operations. These inputs include signal status, detector call status (including pedestrian calls), preempt status, and coordination status. The analysis tool then analyzes the log files for each day and produces user-friendly reports in hourly average and cycle-based formats. The measures of effectiveness produced by the tool include signal data (e.g., phase time, phase failures, queue clearance time), pedestrian data (e.g., pedestrian calls per hour and average time to service pedestrian), and preempt data (e.g., type of preempt, time of preempt, and duration of preempt). The analyst can install the tool in the signal cabinet and log the data for subsequent evaluation and troubleshooting in the office. The tool was deployed and field-evaluated at two signalized intersections in Texas. The results generated from the tool were found to be in good agreement with observations at the test sites.