Travel time is an important performance measure used to assess the traffic operational quality of various types of highway facilities. Previous research funded by the Florida Department of Transportation (FDOT) on travel time reliability developed, implemented, and evaluated tools for estimating travel time reliability for freeways and arterials. These efforts also compared the model-estimated travel times to field-measured travel times using various sources of data. Given the variety and diversity of travel time measurement methods, it is important to evaluate the accuracy of the data obtained by each of them and to develop recommendations regarding their suitability in the validation of travel time estimation models as well as in the development of real-time travel time reliability metrics. The main objective of this research was to collect field data along several freeways and arterials and to evaluate the travel time measurements obtained by STEWARD, INRIX, BlueTOAD, and HERE. The research team collected data with the use of an instrumented vehicle on five freeway segments and two arterial segments in Florida. The field-measured travel times were statistically compared with the travel times provided through the methods listed above. The results of the statistical comparison suggest that the HERE traffic data provide better freeway travel time estimates, compared to the remaining methods. HERE traffic is more accurate for oversaturated conditions. On the other hand, when analyzing uncongested freeway segments, STEWARD, INRIX, and BlueTOAD performed better than HERE traffic. Lastly, analysis at the arterial sites suggested that none of the methods was accurate, although the sample size was relatively small, especially during the oversaturated runs.