The paths of 2425 individual motorcycle trips made in London
were analyzed in order to uncover the route choice decisions made
by drivers. The paths were derived from global positioning system (GPS)
data collected by a courier company for each of their drivers, using algorithms
developed for the purpose of this paper. Motorcycle couriers were
chosen due to the fact that they both know streets very well and that
they do not rely on the GPS to guide their navigation. Each trace was
mapped to the underlying road network, and two competing hypotheses
for route choice decisions were compared: (a) that riders attempt to
minimize the Manhattan distance between locations and (b) that they
attempt to minimize the angular distance. In each case, the distance actually
traveled was compared to the minimum possible either block or
angular distance through the road network. It is usually believed that
drivers who know streets well will navigate trips that reduce Manhattan
distance; however, here it is shown that angularity appears to play an
important role in route choice. 63% of trips made took the minimum
possible angular distance between origin and destination, while 51% of
trips followed the minimum possible block distance. This implies that
impact of turns on cognitive distance plays an important role in decision
making, even when a driver has good knowledge of the spatial network
