Why open apertures and generous x-height improve transit signage speed.
AWhen commuters hurry through crowded underground rail interchanges, signage legibility depends on split-second character recognition from oblique angles. Type designers therefore avoid tightly closed letterforms like 'c', 'e', and 'a', preferring wide apertures that resist optical blurring under dim tunnel lighting.
BFollowing Margaret Calvert and Jock Kinneir's 1960s British highway typeface overhaul, empirical eye-tracking trials confirmed that mixed-case lettering outperforms all-capitals because distinctive word silhouettes speed reading recognition by nearly 15 percent.
Eye-tracking studies found all-uppercase highway signs are recognised faster than mixed-case wording.