The Effect of Font Weight and Rendering System on Glance-Based Text Legibility

In-vehicle user interfaces increasingly rely on digital text to display information to the driver. Led by Apple's iOS, thin, lightweight typography has become increasingly popular in cutting-edge HMI designs. The legibility trade-offs of lightweight typography are sparsely studied, particularly in the glance-like reading scenarios necessitated by driving. Previous research has shown that even relatively subtle differences in the design of the on-screen typeface can influence to-device glance time in a measurable and meaningful way. Here we investigate the relative legibility of four different weights (line thicknesses) of type under two different rendering systems (suboptimal rendering and optimal rendering). Results indicate that under suboptimal rendering, the lightest weight typeface renders poorly and is associated with markedly degraded legibility. Under optimal rendering, lighter weight typefaces show enhanced legibility compared to heavier typefaces. The reasons for this pattern of results, and its implications for design considerations in modern HMIs, are discussed.