**Lucia Vigoroso, Federica Caffaro \* and Eugenio Cavallo**

Institute for Agricultural and Earthmoving Machines (IMAMOTER), National Research Council of Italy (CNR), Strada delle Cacce, 73–10135 Torino, Italy; l.vigoroso@ima.to.cnr.it (L.V.); eugenio.cavallo@cnr.it (E.C.) **\*** Correspondence: f.caffaro@ima.to.cnr.it; Tel.: +39-011-39-77-720

Received: 18 December 2018; Accepted: 17 February 2019; Published: 20 February 2019

**Abstract:** Steep slopes are the main cause of rollover incidents in agriculture. Targeted safety signs have been developed to warn machinery operators against risky slopes. However, machinery user's manuals and road signs report information regarding slope steepness in two different ways, by using the tilt angle in degrees and the slope percentage, respectively. In this study, we investigated the comprehension of safety signs depicting critical slopes, either in degrees or as percent values in a group of Italian agricultural machinery operators while considering the possible influence of previous experience with agricultural machinery, previous incidents, and on-farm occupation. Eighteen tractor and self-propelled machinery operators were administered graphical representations of seven slope angles in a randomized order and then were asked to estimate the slope steepness as both a tilt angle and a slope percentage. The participants tended to overestimate slope steepness in degrees, whereas the opposite was true for percentages. Farmers who were previously involved in a machinery-related incident were more accurate in their estimates. The present results raise some considerations regarding the need to redesign safety communication and to promote targeted training interventions.

**Keywords:** agriculture; injury risk; occupational safety; road sign comprehension; slope angle; warning sign
