  The growth of transportation networks and their increasing interconnections,
although positive, has the downside effect of an increasing complexity which
make them difficult to use, to assess, and limits their efficiency. On average
in the UK, 23% of travel time is lost in connections for trips with more than
one mode, and the lack of synchronization decreases very slowly with population
size. This lack of synchronization between modes induces differences between
the theoretical quickest trip and the `time-respecting' path, which takes into
account waiting times at interconnection nodes. We analyse here the statistics
of these paths on the multilayer, temporal network of the entire, multimodal
british public transportation system. We propose a statistical decomposition --
the `anatomy' -- of trips in urban areas, in terms of riding, waiting and
walking times, and which shows how the temporal structure of trips varies with
distance and allows us to compare different cities. Weaknesses in systems can
be either insufficient transportation speed or service frequency, but the key
parameter controlling their global efficiency is the total number of stop
events per hour for all modes. This analysis suggests the need for better
optimization strategies, adapted to short, long unimodal or multimodal trips.
