The Overloaded Bus Shelter Poster
A city transport authority wants a single poster for a bus shelter at a busy junction. The shelter's display panel is 1.2 m wide × 1.8 m tall, viewed by pedestrians from 1–4 m and by motorists from 8–15 m. The brief says the poster must communicate the new night-service timetable, a QR code to a route planner, and a safety slogan. The client insists all three be 'equally prominent.' The designer has a 3-colour print budget and 48 hours. Pedestrians walk past at roughly 1.4 m/s; motorists pass at 30–50 km/h. The junction is lit at night but the panel faces away from the main light source after 8 pm.
1. Should the designer accept the 'all three equally prominent' instruction as written? Justify with a viewing-distance and dwell-time argument, and propose a hierarchy.
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No. Equal prominence is physically impossible to execute honestly here because the two audiences have incompatible dwell times.
- Pedestrian at 1.4 m/s crossing a ~2 m viewing cone gets roughly 1.5 s of attention - enough for one headline and maybe a QR code if it is large.
- Motorist at 30–50 km/h has under 0.5 s and cannot read body text at all; they can register one high-contrast shape or slogan.
So the poster needs a primary, secondary, tertiary order rather than three co-equal elements. A defensible hierarchy: (1) safety slogan as the largest, highest-contrast element readable at speed; (2) QR code at a size that a stationary pedestrian can scan (roughly 15–20 cm square at 1–2 m); (3) timetable details as the smallest block, since a pedestrian who stops will read it, and a motorist never will.
The designer should push back with this reasoning rather than silently comply - the brief's intent (reach both audiences) is served by hierarchy, not by flattening everything to the same weight.
2. The panel is poorly lit after 8 pm. How should this change the colour and contrast decisions within a 3-colour budget?
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Poor lighting inverts normal contrast logic: dark text on a light ground becomes unreadable in dim conditions because the light ground reflects little and the eye loses edge definition, while light elements on a dark ground stay legible longer.
With three inks, a strong allocation is: a dark ground (e.g. deep navy or charcoal), a light ink (white or cream) for the slogan and QR quiet zone, and one saturated accent reserved for a single call to action or the safety icon. This spends the accent where it earns attention and keeps the QR code high-contrast (dark modules on light, or inverted only if tested - many scanners fail on inverted codes, so the QR should sit on a light patch within the dark field).
The designer must also check the QR code's quiet zone and module contrast survive the lighting, and avoid relying on subtle hue differences that vanish at low light. The 3-colour budget is not the constraint - the constraint is preserving edge contrast under dim viewing.