A pseudo-3D visual variable for simultaneous risk mapping and safest route communication

Routing applications are integral to daily life, providing reliable route planning on smartphones and the web. Despite their utility, adequate visualization of recommended paths tailored to individual user requests is often overlooked. Current route maps typically use standard visual variables like color and symbols to represent traffic conditions or road types. However, when communicating situations beyond traffic efficiency, such as areas of potential risk (e.g., high concentrations of particulate matter), these visualizations may not be appropriate. To address this, we introduce a pseudo-3D visual variable as an alternative method for risk mapping and safe route communication. The proposed technique specifically highlights out-of-danger paths, guiding travelers to avoid risk zones and nudging them toward safer routes. A user study demonstrated that this visualization significantly influences route choice behavior, with over 65% of participants favoring the safest route over the fastest when the pseudo-3D visualizations were applied. Additionally, a prototype web application was developed to showcase the practical application of this visualization in a realistic routing scenario.