Research shows how 'navigational
hazards' in metro maps confuse travelers
May 17, 2018
B. Lloyd, a PhD student in the School of Computing, working alongside Dr
Peter Rodgers in the same department, and Dr Maxwell J. Roberts, a
cognitive psychologist at the University of Essex, is carrying out a
series of studies on the New York City subway map. This is sometimes
ranked as the most complex metro map in the world, but the results are
expected to be applicable to other cities.
The researchers recruited 300 participants online to use an on-screen
map to plan a number of journeys between randomly selected pairs of
stations. Each journey contained one or more 'navigational hazard' such
as where one route switched places with another route, merged with
another route or trunk, or passed under another trunk.
The initial aim of the study was to determine the effect of commonly
used colour-coding schemes on the usability of the map as measured by
accuracy and speed of navigation.
The three colour-coding schemes studied were: 'route colouring' where
each end-to-end route is coloured distinctly; 'trunk colouring' where
routes are coloured according to the trunks they run along; and the
intermediate 'shade colouring' (shown below). Participants' performance
when navigating from one station to another was determined by recording
how many mistakes they made and how long they took to complete each
Their results are consistent with what the researchers predicted: in
planning simple journeys with at most one change, the route-coloured map
scored the highest usability, while in planning complex journeys with
multiple changes, the trunk-coloured map scored the highest usability.
A surprising outcome from the study is the large effect on usability of
navigational hazards - specific local features in the map that are
frequently misread by passengers. The researchers found that some
navigational hazards affect the usability score more than the choice of
colour-coding scheme does and that a few specific navigational hazards
reverse the general trend of the effect of colour coding.
example, on routes with slip hazards - where two routes converge as one
- route colouring remained the fastest and most accurate means of
identifying the correct route. But on routes with jump hazards - where
riders have to move from one branch line to another - it was the least
effective and trunk colouring was more effective.
The researchers are now carrying out further analyses of the dataset to
characterize navigational hazards with a view to developing software for
automated detection and correction of those hazards.
The paper, Metro Map Colour-Coding: Effect on Usability in Route
Tracing, is being presented at the conference Diagrams2018 in Edinburgh
on June 18-22 and presented at the Transit Mapping Symposium, a meeting
of academics and industry representatives, on 28-29 June in Montreal,