A methodology to assess the comprehension of interpretation signs is proposed. A set of parameters to evaluate the legibility and readability characteristics collected from the literature are classified. Forty use items on panels from walking routes from Spain have been collected and tested with our methodology. Later, these parameters were computed semi-automatically, and the degree of compliance regarding these aspects was calculated. Also, a survey was performed to study the visitors' experience. Panels from each track have been evaluated by five people in three levels, under a set of established criteria. A classifying model has been computed showing that comprehension depends on both legibility and readability. Model accuracy is 0.75. The results help us to establish the relative importance of each aspect. Interpretative panels have a cultural value with socio-economic impact. This study could be helpful to design better informative panels in the future.